Exploring the quantum advantages of various non-classical quantum states in noisy environments is a central subject in quantum sensing.Here we provide a complete picture for the frequency estimation precision of three...Exploring the quantum advantages of various non-classical quantum states in noisy environments is a central subject in quantum sensing.Here we provide a complete picture for the frequency estimation precision of three important states(the Greenberger-Horne-Zeilinger(GHZ)state,the maximal spin squeezed state,and the spin coherent state)of a spin-S under both individual dephasing and collective dephasing by general Gaussian noise,ranging from the Markovian limit to the extreme non-Markovian limit.Whether or not the noise is Markovian,the spin coherent state is always worse than the classical scheme under collective dephasing although it is equivalent to the classical scheme under individual dephasing.Moreover,the maximal spin squeezed state always give the best sensing precision(and outperforms the widely studied GHZ state)in all cases.This establishes the general advantage of the spin squeezed state for noisy frequency estimation in many quantum sensing platforms.展开更多
Inspired by the recent discovery of breathing kagome materials Nb_(3)Cl_(8) and Nb_(3)TeCl_(7),we have explored the influence of the breathing effect on the Hubbard model of the kagome lattice.Utilizing the determinan...Inspired by the recent discovery of breathing kagome materials Nb_(3)Cl_(8) and Nb_(3)TeCl_(7),we have explored the influence of the breathing effect on the Hubbard model of the kagome lattice.Utilizing the determinant quantum Monte Carlo method,we first investigated the average sign problem in the breathing kagome lattice,which is influenced by both the breathing strength and the interaction strength.Secondly,we calculated the electronic kinetic energy,the direct current conductivity,and the electronic density of states at the Fermi level to determine the critical interaction strength for the metal-insulator transition.Our results indicate that the breathing effect,in conjunction with the interaction strength,drives the kagome system from a metal to an insulator.Finally,we evaluated the magnetic properties and constructed a phase diagram incorporating both transport and magnetic properties.The phase diagram reveals that as the interaction strength increases,the system transitions from a paramagnetic metal to a Mott insulator.Our research provides theoretical guidance for utilizing the breathing effect to control the band gaps,conductivity,and magnetic properties of kagome materials with electronic interactions.展开更多
Finding the optimal control is of importance to quantum metrology under a noisy environment.In this paper,we tackle the problem of finding the optimal control to enhance the performance of quantum metrology under an a...Finding the optimal control is of importance to quantum metrology under a noisy environment.In this paper,we tackle the problem of finding the optimal control to enhance the performance of quantum metrology under an arbitrary non-Markovian bosonic environment.By introducing an equivalent pseudomode model,the non-Markovian dynamic evolution is reduced to a Lindblad master equation,which helps us to calculate the gradient of quantum Fisher information and perform the gradient ascent algorithm to find the optimal control.Our approach is accurate and circumvents the need for the Born-Markovian approximation.As an example,we consider the frequency estimation of a spin with pure dephasing under two types of non-Markovian environments.By maximizing the quantum Fisher information at a fixed evolution time,we obtain the optimal multi-axis control,which results in a notable enhancement in quantum metrology.The advantage of our method lies in its applicability to the arbitrary non-Markovian bosonic environment.展开更多
Single-atom catalysts(SACs)have garnered interest in designing their ligand environments,facilitating the modification of single catalytic sites toward high activity and selectivity.Despite various synthetic approache...Single-atom catalysts(SACs)have garnered interest in designing their ligand environments,facilitating the modification of single catalytic sites toward high activity and selectivity.Despite various synthetic approaches,it remains challenging to achieve a catalytically favorable coordination structure simultaneously with the feasible formation of SACs at low temperatures.Here,a new type of coordination structure for Pt SACs is introduced to offer a highly efficient hydrogen evolution reaction(HER)catalyst,where Pt SACs are readily fabricated by atomically confining PtCl_(2)on chemically driven NO_(2)sites in two-dimensional nitrogen-doped carbon nanosheets at room temperature.The resultant Pt SACs form the NO_(2)-Pt-Cl_(2)coordination structure with an atomic dispersion,as revealed by X-ray spectroscopy and transmission electron microscopy investigations.Moreover,our first-principles density functional theory(DFT)calculations show strong interactions in the coordination by computing the binding energy and charge density difference between PtCl_(2)and NO_(2).Pt SACs,established on the NO_(2)-functionalized carbon support,demonstrate the onset potential of 25 mV,Tafel slope of 40 mV dec^(-1),and high specific activity of 1.35 A mgPt^(-1).Importantly,the Pt SACs also exhibit long-term stability up to 110 h,which is a significant advance in the field of single-atom Pt catalysts.The newly developed coordination structure of Pt SACs features a single Pt active center,providing hydrogen binding ability comparable to that of Pt(111),enhanced long-term durability due to strong metal-support interactions,and the advantage of room-temperature fabrication.展开更多
Control of hyperfine interaction strength of shallow donors in Si is one of the central issues in realizing Kane quantum computers.First-principles calculations on the hyperfine Stark shift of shallow donors are chall...Control of hyperfine interaction strength of shallow donors in Si is one of the central issues in realizing Kane quantum computers.First-principles calculations on the hyperfine Stark shift of shallow donors are challenging since large supercells are needed to accommodate the delocalized donor wave functions.In this work,we investigated the hyperfine Stark shift and its strain tunability for shallow donors P and As in Si using the potential patching method based on first-principles density functional theory calculations.The good agreement between our calculations and experimental results confirms that the potential patching method is a feasible and accurate first-principles approach for studying wave-function-related properties of shallow impurities,such as the Stark shift parameter.It is further shown that the application of strain expands the range of hyperfine Stark shift and helps improve the response of shallow donor based qubit gates.The results could be useful for developing quantum computing architectures based on shallow donors in Si.展开更多
The incorporation of graphene fillers into polymer matrices has been recognized for its potential to enhance thermal conductivity,which is particularly beneficial for applications in thermal management.The uniformity ...The incorporation of graphene fillers into polymer matrices has been recognized for its potential to enhance thermal conductivity,which is particularly beneficial for applications in thermal management.The uniformity of graphene dispersion is pivotal to achieving optimal thermal conductivity,thereby directly influencing the effectiveness of thermal management,including the mitigation of local hot-spot temperatures.This research employs a quantitative approach to assess the distribution of graphene fillers within a PBX(plastic-bonded explosive)matrix,focusing specifically on the thermal management of hot spots.Through finite element method(FEM)simulations,we have explored the impact of graphene filler orientation,proximity to the central heat source,and spatial clustering on heat transfer.Our findings indicate that the strategic distribution of graphene fillers can create efficient thermal conduction channels,which significantly reduce the temperatures at local hot spots.In a model containing 0.336%graphene by volume,the central hot-spot temperature was reduced by approximately 60 K compared to a pure PBX material,under a heat flux of 600 W/m^(2).This study offers valuable insights into the optimization of the spatial arrangement of low-concentration graphene fillers,aiming to improve the thermal management capabilities of HMX-based PBX explosives.展开更多
It is well known that the A-square term must be considered in both cavity and circuit quantum electrodynamics systems,because it arises in the derivation from the minimal coupling Hamiltonian at any finite coupling st...It is well known that the A-square term must be considered in both cavity and circuit quantum electrodynamics systems,because it arises in the derivation from the minimal coupling Hamiltonian at any finite coupling strength.In this paper,we study the quantum Rabi model with A-square terms using the Bogoliubov operator approach.After a unitary transformation,the A-square terms can be eliminated,resulting in a modified quantum Rabi model with renormalized parameters.A transcendental function responsible for the exact solution is then derived.The presence of the A-square terms is found to significantly alter the energy spectrum.The dynamics are also studied using the obtained exact wave function,which is sensitive to the strength of the A-square terms at strong coupling.We believe that these results could be observed in future light–matter interaction systems in the ultra-strong and deep strong coupling regimes.展开更多
Lattice distortion of materials has a profound impact on their electronic and magnetic properties,which can generate local magnetic states in intrinsically non-magnetic systems.Here we report on the realization of a o...Lattice distortion of materials has a profound impact on their electronic and magnetic properties,which can generate local magnetic states in intrinsically non-magnetic systems.Here we report on the realization of a one-dimensional(1D)magnetic stripe in monolayer H-NbSe_(2)sustained by strain along the terraces of the graphene/SiC substrates.The strength of this tensile strain is widely tunable by the height-to-width ratio of the terraces.Increasing the tensile strength leads to the shifts and splitting of the Nb 4d bands crossing the Fermi energy,generating spin polarization in a 1D magnetic stripe along the terrace.Simultaneously,the charge-densitywave signature of strained H-NbSe_(2)is significantly suppressed.Such a magnetic stripe can be locally quenched by an individual Se-atom defect via the defect-induced Jahn-Teller distortion and charge density redistribution.These findings provide a different route to achieving and manipulating 1D magnetism in otherwise non-magnetic systems,offering a new way for spintronic devices.展开更多
The glass-forming ability(GFA)of metallic glasses is a key scientific challenge in their development and application,with compositional dependence playing a crucial role.Experimental studies have demonstrated that the...The glass-forming ability(GFA)of metallic glasses is a key scientific challenge in their development and application,with compositional dependence playing a crucial role.Experimental studies have demonstrated that the addition of specific minor elements can greatly enhance the GFA of parent alloys,yet the underlying mechanism remains unclear.In this study,we use the ZrCuAl system as a model to explore how the addition of minor Al influences the crystallization rate by modulating the properties of the crystal-liquid interface,thereby affecting the GFA.The results reveal that the minor addition of Al significantly reduces the crystal growth rate,a phenomenon not governed by particle density fluctuations at the interface.The impact of minor element additions extends beyond a modest increase in crystal-unfavorable motifs in the bulk supercooled liquid.More importantly,it leads to a significant enrichment of these motifs at the crystal-supercooled liquid interface,forming a dense topological network of crystal-unfavorable structures that effectively prevent the growth of the crystalline interface and enhance GFA.Our results provide valuable insights for the design and development of high-performance metallic glasses.展开更多
The Josephson junction is typically tuned by a magnetic field or electrostatic gate to realize a superconducting(SC)transistor,which manipulates the supercurrent in integrated SC circuits.Here,we propose a theoretical...The Josephson junction is typically tuned by a magnetic field or electrostatic gate to realize a superconducting(SC)transistor,which manipulates the supercurrent in integrated SC circuits.Here,we propose a theoretical scheme for a light-controlled SC transistor,which is composed of two superconductor leads weakly linked by a coherent light-driven quantum dot.We discover a Josephson-like relation for the supercurrent I=I(Φ)sinΦsc,where both the supercurrent phaseΦand magnitude Iccan be completely controlled by the phase,intensity,and detuning of the driving light.Additionally,the supercurrent magnitude displays a Fano profile with the increase of the driving light intensity,which is understood by comparing the level splitting of the quantum dot under light driving with the SC gap.Moreover,when two such SC transistors form a loop,they constitute a light-controlled SC quantum interference device(SQUID).Such a light-controlled SQUID can demonstrate the Josephson diode effect,and the optimized non-reciprocal efficiency achieves up to 54%,surpassing the maximum record reported in recent literature.Thus,our scheme delivers a promising platform for performing diverse and flexible manipulations in SC circuits.展开更多
Co_(3)O_(4)possesses both direct and indirect oxidation effects and is considered as a promising catalyst for the oxidation of 5-hydroxymethylfurfural(HMF).However,the enrichment and activation effects of Co_(3)O_(4)o...Co_(3)O_(4)possesses both direct and indirect oxidation effects and is considered as a promising catalyst for the oxidation of 5-hydroxymethylfurfural(HMF).However,the enrichment and activation effects of Co_(3)O_(4)on OH-and HMF are weak,which limits its further application.Metal defect engineering can regulate the electronic structure,optimize the adsorption of intermediates,and improve the catalytic activity by breaking the symmetry of the material,which is rarely involved in the upgrading of biomass.In this work,we prepare Co_(3)O_(4)with metal defects and load the precious metal platinum at the defect sites(PtVco).The results of in-situ characterizatio ns,electrochemical measurements,and theoretical calculations indicate that the reduction of Co-Co coordination number and the formation of Pt-Co bond induce the decrease of electron filling in the antibonding orbitals of Co element.The resulting upward shift of the d-band center of Co combined with the characteristic adsorption of Pt species synergically enhances the enrichment and activation of organic molecules and OH species,thus exhibiting excellent HMF oxidation activity(including a lower onset potential(1.14 V)and 19 times higher current density than pure Co_(3)O_(4)at 1.35 V).In summary,this work explores the adsorption enhancement mechanism of metal defect sites modified by precious metal in detail,provides a new option for improving the HMF oxidation activity of cobalt-based materials,broadens the application field of metal defect based materials,and gives an innovative guidance for the functional utilization of metal defect sites in biomass conversion.展开更多
CXCR1 is a G-protein coupled receptor, transducing signals from chemokines, in particular the interleukin-8 （1L8） molecules. This study combines homology modeling and molecular dynamics simulation methods to study t...CXCR1 is a G-protein coupled receptor, transducing signals from chemokines, in particular the interleukin-8 （1L8） molecules. This study combines homology modeling and molecular dynamics simulation methods to study the structure of CXCRI-IL8 complex. By using CXCR4-vMIP-II crystallography structure as the homologous template, CXCRI-IL8 complex structure was constructed, and then refined using all-atom molecular dynamics simulations. Through extensive simulations, CXCRI-IL8 binding poses were investigated in detail. Furthermore, the role of the N-terminal of CXCR1 receptor was studied by comparing four complex models differing in the N-terminal sequences. The results indicate that the receptor N-terminal affects the binding of IL8 significantly. With a shorter N-terminal domain, the binding of IL8 to CXCR1 becomes unstable. The homology modeling and simulations also reveal the key receptor-ligand residues involved in the electrostatic interactions known to be vital for complex formation.展开更多
Polymerases are protein enzymes that move along nucleic acid chains and catalyze template-based polymerization reactions during gene transcription and replication. The polymerases also substantially improve transcript...Polymerases are protein enzymes that move along nucleic acid chains and catalyze template-based polymerization reactions during gene transcription and replication. The polymerases also substantially improve transcription or replica- tion fidelity through the non-equilibrium enzymatic cycles. We briefly review computational efforts that have been made toward understanding mechano--chemical coupling and fidelity control mechanisms of the polymerase elongation. The polymerases are regarded as molecular information motors during the elongation process. It requires a full spectrum of computational approaches from multiple time and length scales to understand the full polymerase functional cycle. We stay away from quantum mechanics based approaches to the polymerase catalysis due to abundant former surveys, while ad- dressing statistical physics modeling approaches along with all-atom molecular dynamics simulation studies. We organize this review around our own modeling and simulation practices on a single subunit T7 RNA polymerase, and summarize commensurate studies on structurally similar DNA polymerases as well. For multi-subunit RNA polymerases that have been actively studied in recent years, we leave systematical reviews of the simulation achievements to latest computational chemistry surveys, while covering only representative studies published very recently, including our own work modeling structure-based elongation kinetic of yeast RNA polymerase II. In the end, we briefly go through physical modeling on elongation pauses and backtracking activities of the multi-subunit RNAPs. We emphasize on the fluctuation and control mechanisms of the polymerase actions, highlight the non-equilibrium nature of the operation system, and try to build some perspectives toward understanding the polymerase impacts from the single molecule level to a genome-wide scale.展开更多
We investigate the quantum dynamics of two defect centers in solids,which are coupled by vacuum-induced dipole-dipole interactions.When the interaction between defects and phonons is taken into account,the two coupled...We investigate the quantum dynamics of two defect centers in solids,which are coupled by vacuum-induced dipole-dipole interactions.When the interaction between defects and phonons is taken into account,the two coupled electron-phonon systems make up two equivalent multilevel atoms.By making Born-Markov and rotating wave approximations,we derive a master equation describing the dynamics of the coupled multilevel atoms.The results indicate the concepts of subradiant and superradiant states can be applied to these systems and the population transfer process presents different behaviors from those of the two dipolar-coupled two-level atoms due to the participation of phonons.展开更多
Rechargeable magnesium-metal batteries(RMMBs)are promising next-generation secondary batteries;however,their development is inhibited by the low capacity and short cycle lifespan of cathodes.Although various strategie...Rechargeable magnesium-metal batteries(RMMBs)are promising next-generation secondary batteries;however,their development is inhibited by the low capacity and short cycle lifespan of cathodes.Although various strategies have been devised to enhance the Mg^(2+)migration kinetics and structural stability of cathodes,they fail to improve electronic conductivity,rendering the cathodes incompatible with magnesium-metal anodes.Herein,we propose a dual-defect engineering strategy,namely,the incorporation of Mg^(2+)pre-intercalation defect(P-Mgd)and oxygen defect(Od),to simultaneously improve the Mg^(2+)migration kinetics,structural stability,and electronic conductivity of the cathodes of RMMBs.Using lamellar V_(2)O_(5)·nH_(2)O as a demo cathode material,we prepare a cathode comprising Mg_(0.07)V_(2)O_(5)·1.4H_(2)O nanobelts composited with reduced graphene oxide(MVOH/rGO)with P-Mgd and Od.The Od enlarges interlayer spacing,accelerates Mg^(2+)migration kinetics,and prevents structural collapse,while the P-Mgd stabilizes the lamellar structure and increases electronic conductivity.Consequently,the MVOH/rGO cathode exhibits a high capacity of 197 mAh g^(−1),and the developed Mg foil//MVOH/rGO full cell demonstrates an incredible lifespan of 850 cycles at 0.1 A g^(−1),capable of powering a light-emitting diode.The proposed dual-defect engineering strategy provides new insights into developing high-durability,high-capacity cathodes,advancing the practical application of RMMBs,and other new secondary batteries.展开更多
To investigate the influences of co-flowand counter-flowmodes of reactant flowarrangement on a proton exchange membrane fuel cell(PEMFC)during start-up,unsteady physical and mathematical models fully coupling the flow...To investigate the influences of co-flowand counter-flowmodes of reactant flowarrangement on a proton exchange membrane fuel cell(PEMFC)during start-up,unsteady physical and mathematical models fully coupling the flow,heat,and electrochemical reactions in a PEMFC are established.The continuity equation and momentum equation are solved by handling pressure-velocity coupling using the SIMPLE algorithm.The electrochemical reaction rates in the catalyst layers(CLs)of the cathode and anode are calculated using the Butler-Volmer equation.The multiphase mixture model describes the multiphase transport process of gas mixtures and liquid water in the fuel cell.After validation,the influences of co-flow and counter-flow modes on the PEMFC performance are investigated,including the evolution of the current density,flow field,temperature field,and reactant concentration field during start-up,as well as the steady distribution of the current density,reactant concentration,andmembrane water content when the start-up stabilizes.Co-flow and counter-flow modes influence the current density distribution and temperature distribution.On the one hand,the co-flow mode accelerates the start-up process of the PEMFC and leads to a more evenly distributed current density than the counter-flow mode.On the other hand,the temperature difference between the inlet and outlet sections of the cell is up to 10.1℃ under the co-flow mode,much larger than the 5.0℃ observed in the counter-flow mode.Accordingly,the counter-flowmode results in a more evenly distributed temperature and a lower maximum temperature than the co-flow case.Therefore,in the flow field design of a PEMFC,the reactant flow arrangements can be considered to weigh between better heat management and higher current density distribution of the cell.展开更多
The combination of non-Hermitian physics and Majorana fermions can give rise to new effects in quantum transport systems. In this work, we investigate the interplay of PT-symmetric complex potentials, Majorana tunneli...The combination of non-Hermitian physics and Majorana fermions can give rise to new effects in quantum transport systems. In this work, we investigate the interplay of PT-symmetric complex potentials, Majorana tunneling and interdot tunneling in a non-Hermitian double quantum dots system. It is found that in the weak-coupling regime the Majorana tunneling has pronounced effects on the transport properties of such a system, manifested as splitting of the single peak into three and a reduced 1/4 peak in the transmission function. In the presence of the PT-symmetric complex potentials and interdot tunneling, the 1/4 central peak is robust against them, while the two side peaks are tuned by them. The interdot tunneling only induces asymmetry, instead of moving the conductance peak, due to the robustness of the Majorana modes. There is an exceptional point induced by the union of Majorana tunneling and interdot tunneling. With increased PT-symmetric complex potentials, the two side peaks will move towards each other. When the exceptional point is passed through, these two side peaks will disappear. In the strong-coupling regime, the Majorana fermion induces a 1/4 conductance dip instead of the three-peak structure. PT-symmetric complex potentials induce two conductance dips pinned at the exceptional point. These effects should be accessible in experiments.展开更多
Semiconductor devices are often operated at elevated temperatures that are well above zero Kelvin,which is the temperature in most first-principles density functional calculations.Computational approaches to com-putin...Semiconductor devices are often operated at elevated temperatures that are well above zero Kelvin,which is the temperature in most first-principles density functional calculations.Computational approaches to com-puting and understanding the properties of semiconductors at finite temperatures are thus in critical demand.In this review,we discuss the recent progress in computationally assessing the electronic and phononic band structures of semiconductors at finite temperatures.As an emerging semiconductor with particularly strong temperature-induced renormalization of the electronic and phononic band structures,halide perovskites are used as a representative example to demonstrate how computational advances may help to understand the band struc-tures at elevated temperatures.Finally,we briefly illustrate the remaining computational challenges and outlook promising research directions that may help to guide future research in this field.展开更多
The application of the eigenstate thermalization hypothesis to non-Hermitian quantum systems has become one of the most important topics in dissipative quantum chaos, recently giving rise to intense debates. The proce...The application of the eigenstate thermalization hypothesis to non-Hermitian quantum systems has become one of the most important topics in dissipative quantum chaos, recently giving rise to intense debates. The process of thermalization is intricate, involving many time-evolution trajectories in the reduced Hilbert space of the system. By considering two different expansion forms of the density matrices adopted in the biorthogonal and right-state time evolutions, we derive two versions of the Gorini–Kossakowski–Sudarshan–Lindblad(GKSL)master equations describing the non-Hermitian systems coupled to a bosonic heat bath in thermal equilibrium. By solving the equations, we identify a sufficient condition for thermalization under both time evolutions, resulting in Boltzmann biorthogonal and right-eigenstate statistics, respectively. This finding implies that the recently proposed biorthogonal random matrix theory needs an appropriate revision. Moreover, we exemplify the precise dynamics of thermalization and thermodynamic properties with test models.展开更多
Materials for deep-ultraviolet(DUV)light emission are extremely rare,significantly limiting the development of efficient DUV light-emitting diodes.Here we report CsMg(I_(1−x)Br_(x))_(3) alloys as potential DUV light e...Materials for deep-ultraviolet(DUV)light emission are extremely rare,significantly limiting the development of efficient DUV light-emitting diodes.Here we report CsMg(I_(1−x)Br_(x))_(3) alloys as potential DUV light emitters.Based on rigorous first-principles hybrid functional calculations,we find that CsMgI_(3) has an indirect bandgap,while CsMgBr_(3) has a direct bandgap.Further,we employ a band unfolding technique for alloy supercell calculations to investigate the critical Br concentration in CsMg(I_(1−x)Br_(x))_(3) associated with the crossover from an indirect to a direct bandgap,which is found to be∼0.36.Thus,CsMg(I_(1−x)Br_(x))_(3) alloys with 0.366≤6≤1 cover a wide range of direct bandgap(4.38–5.37 eV;284–231 nm),falling well into the DUV regime.Our study will guide the development of efficient DUV light emitters.展开更多
基金supported by the National Natural Science Foundation of China(NSFC)Grant No.12274019the NSAF grant in NSFC with Grant No.U2230402。
文摘Exploring the quantum advantages of various non-classical quantum states in noisy environments is a central subject in quantum sensing.Here we provide a complete picture for the frequency estimation precision of three important states(the Greenberger-Horne-Zeilinger(GHZ)state,the maximal spin squeezed state,and the spin coherent state)of a spin-S under both individual dephasing and collective dephasing by general Gaussian noise,ranging from the Markovian limit to the extreme non-Markovian limit.Whether or not the noise is Markovian,the spin coherent state is always worse than the classical scheme under collective dephasing although it is equivalent to the classical scheme under individual dephasing.Moreover,the maximal spin squeezed state always give the best sensing precision(and outperforms the widely studied GHZ state)in all cases.This establishes the general advantage of the spin squeezed state for noisy frequency estimation in many quantum sensing platforms.
基金supported by the National Science Foundation of China(Grant No.12474218)Beijing Natural Science Foundation(Grant Nos.1242022 and 1252022).
文摘Inspired by the recent discovery of breathing kagome materials Nb_(3)Cl_(8) and Nb_(3)TeCl_(7),we have explored the influence of the breathing effect on the Hubbard model of the kagome lattice.Utilizing the determinant quantum Monte Carlo method,we first investigated the average sign problem in the breathing kagome lattice,which is influenced by both the breathing strength and the interaction strength.Secondly,we calculated the electronic kinetic energy,the direct current conductivity,and the electronic density of states at the Fermi level to determine the critical interaction strength for the metal-insulator transition.Our results indicate that the breathing effect,in conjunction with the interaction strength,drives the kagome system from a metal to an insulator.Finally,we evaluated the magnetic properties and constructed a phase diagram incorporating both transport and magnetic properties.The phase diagram reveals that as the interaction strength increases,the system transitions from a paramagnetic metal to a Mott insulator.Our research provides theoretical guidance for utilizing the breathing effect to control the band gaps,conductivity,and magnetic properties of kagome materials with electronic interactions.
基金supported by the National Natural Science Foundation of China(Grant No.12274019)the NSAF Joint Fund(Grant No.U2230402)。
文摘Finding the optimal control is of importance to quantum metrology under a noisy environment.In this paper,we tackle the problem of finding the optimal control to enhance the performance of quantum metrology under an arbitrary non-Markovian bosonic environment.By introducing an equivalent pseudomode model,the non-Markovian dynamic evolution is reduced to a Lindblad master equation,which helps us to calculate the gradient of quantum Fisher information and perform the gradient ascent algorithm to find the optimal control.Our approach is accurate and circumvents the need for the Born-Markovian approximation.As an example,we consider the frequency estimation of a spin with pure dephasing under two types of non-Markovian environments.By maximizing the quantum Fisher information at a fixed evolution time,we obtain the optimal multi-axis control,which results in a notable enhancement in quantum metrology.The advantage of our method lies in its applicability to the arbitrary non-Markovian bosonic environment.
基金supported by the National Research Foundation of Korea(NRF)(NRF-2020M3H4A3106354,NRF-2021M3I3A1083946,and NRF-2021R1A6A3A01087461)the Korea Institute of Science and Technology,and the KISTI Supercomputing Center(KSC-2023-CRE-0492).
文摘Single-atom catalysts(SACs)have garnered interest in designing their ligand environments,facilitating the modification of single catalytic sites toward high activity and selectivity.Despite various synthetic approaches,it remains challenging to achieve a catalytically favorable coordination structure simultaneously with the feasible formation of SACs at low temperatures.Here,a new type of coordination structure for Pt SACs is introduced to offer a highly efficient hydrogen evolution reaction(HER)catalyst,where Pt SACs are readily fabricated by atomically confining PtCl_(2)on chemically driven NO_(2)sites in two-dimensional nitrogen-doped carbon nanosheets at room temperature.The resultant Pt SACs form the NO_(2)-Pt-Cl_(2)coordination structure with an atomic dispersion,as revealed by X-ray spectroscopy and transmission electron microscopy investigations.Moreover,our first-principles density functional theory(DFT)calculations show strong interactions in the coordination by computing the binding energy and charge density difference between PtCl_(2)and NO_(2).Pt SACs,established on the NO_(2)-functionalized carbon support,demonstrate the onset potential of 25 mV,Tafel slope of 40 mV dec^(-1),and high specific activity of 1.35 A mgPt^(-1).Importantly,the Pt SACs also exhibit long-term stability up to 110 h,which is a significant advance in the field of single-atom Pt catalysts.The newly developed coordination structure of Pt SACs features a single Pt active center,providing hydrogen binding ability comparable to that of Pt(111),enhanced long-term durability due to strong metal-support interactions,and the advantage of room-temperature fabrication.
基金supported by the National Natural Science Foun-dation of China(Grant Nos.12393831 and 12088101).
文摘Control of hyperfine interaction strength of shallow donors in Si is one of the central issues in realizing Kane quantum computers.First-principles calculations on the hyperfine Stark shift of shallow donors are challenging since large supercells are needed to accommodate the delocalized donor wave functions.In this work,we investigated the hyperfine Stark shift and its strain tunability for shallow donors P and As in Si using the potential patching method based on first-principles density functional theory calculations.The good agreement between our calculations and experimental results confirms that the potential patching method is a feasible and accurate first-principles approach for studying wave-function-related properties of shallow impurities,such as the Stark shift parameter.It is further shown that the application of strain expands the range of hyperfine Stark shift and helps improve the response of shallow donor based qubit gates.The results could be useful for developing quantum computing architectures based on shallow donors in Si.
基金supported by the National Natural Science Foundation of China(Grant No.U2330208).
文摘The incorporation of graphene fillers into polymer matrices has been recognized for its potential to enhance thermal conductivity,which is particularly beneficial for applications in thermal management.The uniformity of graphene dispersion is pivotal to achieving optimal thermal conductivity,thereby directly influencing the effectiveness of thermal management,including the mitigation of local hot-spot temperatures.This research employs a quantitative approach to assess the distribution of graphene fillers within a PBX(plastic-bonded explosive)matrix,focusing specifically on the thermal management of hot spots.Through finite element method(FEM)simulations,we have explored the impact of graphene filler orientation,proximity to the central heat source,and spatial clustering on heat transfer.Our findings indicate that the strategic distribution of graphene fillers can create efficient thermal conduction channels,which significantly reduce the temperatures at local hot spots.In a model containing 0.336%graphene by volume,the central hot-spot temperature was reduced by approximately 60 K compared to a pure PBX material,under a heat flux of 600 W/m^(2).This study offers valuable insights into the optimization of the spatial arrangement of low-concentration graphene fillers,aiming to improve the thermal management capabilities of HMX-based PBX explosives.
基金supported by the National Science Foundation of China under Grant Nos.12305009(XYC)and 11834005(QHC)the China Postdoctoral Science Foundation under Grant No.2022M720387(XYC).
文摘It is well known that the A-square term must be considered in both cavity and circuit quantum electrodynamics systems,because it arises in the derivation from the minimal coupling Hamiltonian at any finite coupling strength.In this paper,we study the quantum Rabi model with A-square terms using the Bogoliubov operator approach.After a unitary transformation,the A-square terms can be eliminated,resulting in a modified quantum Rabi model with renormalized parameters.A transcendental function responsible for the exact solution is then derived.The presence of the A-square terms is found to significantly alter the energy spectrum.The dynamics are also studied using the obtained exact wave function,which is sensitive to the strength of the A-square terms at strong coupling.We believe that these results could be observed in future light–matter interaction systems in the ultra-strong and deep strong coupling regimes.
基金supported by the National Key R&D Program of China(Grant Nos.2022YFA1402602,2022YFA1402502,2021YFA1400103,2020YFA0308802,and 2024YFA1611300)the National Natural Science Foundation of China(Grant Nos.92163206,12274026,12321004,12304205,11934003,12393831,and U2230402)+1 种基金Beijing Association for Science and Technology Youth Talent Lift Program,MCIN/AEI/10.13039/501100011033(Grant No.PID2022-140845OB-C66)FEDER Una manera de hacer Europa。
文摘Lattice distortion of materials has a profound impact on their electronic and magnetic properties,which can generate local magnetic states in intrinsically non-magnetic systems.Here we report on the realization of a one-dimensional(1D)magnetic stripe in monolayer H-NbSe_(2)sustained by strain along the terraces of the graphene/SiC substrates.The strength of this tensile strain is widely tunable by the height-to-width ratio of the terraces.Increasing the tensile strength leads to the shifts and splitting of the Nb 4d bands crossing the Fermi energy,generating spin polarization in a 1D magnetic stripe along the terrace.Simultaneously,the charge-densitywave signature of strained H-NbSe_(2)is significantly suppressed.Such a magnetic stripe can be locally quenched by an individual Se-atom defect via the defect-induced Jahn-Teller distortion and charge density redistribution.These findings provide a different route to achieving and manipulating 1D magnetism in otherwise non-magnetic systems,offering a new way for spintronic devices.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.T2325004 and 52161160330)the support from the Hong Kong Institute of Advanced Studies through the materials cluster project。
文摘The glass-forming ability(GFA)of metallic glasses is a key scientific challenge in their development and application,with compositional dependence playing a crucial role.Experimental studies have demonstrated that the addition of specific minor elements can greatly enhance the GFA of parent alloys,yet the underlying mechanism remains unclear.In this study,we use the ZrCuAl system as a model to explore how the addition of minor Al influences the crystallization rate by modulating the properties of the crystal-liquid interface,thereby affecting the GFA.The results reveal that the minor addition of Al significantly reduces the crystal growth rate,a phenomenon not governed by particle density fluctuations at the interface.The impact of minor element additions extends beyond a modest increase in crystal-unfavorable motifs in the bulk supercooled liquid.More importantly,it leads to a significant enrichment of these motifs at the crystal-supercooled liquid interface,forming a dense topological network of crystal-unfavorable structures that effectively prevent the growth of the crystalline interface and enhance GFA.Our results provide valuable insights for the design and development of high-performance metallic glasses.
基金supported by NSF of China(Grant Nos.12088101 and 11905007)NSAF(Grants Nos.U1930403 and U1930402)。
文摘The Josephson junction is typically tuned by a magnetic field or electrostatic gate to realize a superconducting(SC)transistor,which manipulates the supercurrent in integrated SC circuits.Here,we propose a theoretical scheme for a light-controlled SC transistor,which is composed of two superconductor leads weakly linked by a coherent light-driven quantum dot.We discover a Josephson-like relation for the supercurrent I=I(Φ)sinΦsc,where both the supercurrent phaseΦand magnitude Iccan be completely controlled by the phase,intensity,and detuning of the driving light.Additionally,the supercurrent magnitude displays a Fano profile with the increase of the driving light intensity,which is understood by comparing the level splitting of the quantum dot under light driving with the SC gap.Moreover,when two such SC transistors form a loop,they constitute a light-controlled SC quantum interference device(SQUID).Such a light-controlled SQUID can demonstrate the Josephson diode effect,and the optimized non-reciprocal efficiency achieves up to 54%,surpassing the maximum record reported in recent literature.Thus,our scheme delivers a promising platform for performing diverse and flexible manipulations in SC circuits.
基金financially supported by the Natural Science Foundation of Shandong Province(ZR2023QB235,ZR202111240183,ZR2021QF120)the Postdoctoral Science Foundation of China(2022M711956)the Taishan Scholar Program of Shandong Province(tsqnz20231216).
文摘Co_(3)O_(4)possesses both direct and indirect oxidation effects and is considered as a promising catalyst for the oxidation of 5-hydroxymethylfurfural(HMF).However,the enrichment and activation effects of Co_(3)O_(4)on OH-and HMF are weak,which limits its further application.Metal defect engineering can regulate the electronic structure,optimize the adsorption of intermediates,and improve the catalytic activity by breaking the symmetry of the material,which is rarely involved in the upgrading of biomass.In this work,we prepare Co_(3)O_(4)with metal defects and load the precious metal platinum at the defect sites(PtVco).The results of in-situ characterizatio ns,electrochemical measurements,and theoretical calculations indicate that the reduction of Co-Co coordination number and the formation of Pt-Co bond induce the decrease of electron filling in the antibonding orbitals of Co element.The resulting upward shift of the d-band center of Co combined with the characteristic adsorption of Pt species synergically enhances the enrichment and activation of organic molecules and OH species,thus exhibiting excellent HMF oxidation activity(including a lower onset potential(1.14 V)and 19 times higher current density than pure Co_(3)O_(4)at 1.35 V).In summary,this work explores the adsorption enhancement mechanism of metal defect sites modified by precious metal in detail,provides a new option for improving the HMF oxidation activity of cobalt-based materials,broadens the application field of metal defect based materials,and gives an innovative guidance for the functional utilization of metal defect sites in biomass conversion.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11575021,U1530401,and U1430237)the National Research Foundation of Korea(Grant Nos.NRF-2017R1A2B2008483 and NRF-2016R1A6A3A04010213)
文摘CXCR1 is a G-protein coupled receptor, transducing signals from chemokines, in particular the interleukin-8 （1L8） molecules. This study combines homology modeling and molecular dynamics simulation methods to study the structure of CXCRI-IL8 complex. By using CXCR4-vMIP-II crystallography structure as the homologous template, CXCRI-IL8 complex structure was constructed, and then refined using all-atom molecular dynamics simulations. Through extensive simulations, CXCRI-IL8 binding poses were investigated in detail. Furthermore, the role of the N-terminal of CXCR1 receptor was studied by comparing four complex models differing in the N-terminal sequences. The results indicate that the receptor N-terminal affects the binding of IL8 significantly. With a shorter N-terminal domain, the binding of IL8 to CXCR1 becomes unstable. The homology modeling and simulations also reveal the key receptor-ligand residues involved in the electrostatic interactions known to be vital for complex formation.
基金supported by the National Natural Science Foundation(Grant No.11275022)
文摘Polymerases are protein enzymes that move along nucleic acid chains and catalyze template-based polymerization reactions during gene transcription and replication. The polymerases also substantially improve transcription or replica- tion fidelity through the non-equilibrium enzymatic cycles. We briefly review computational efforts that have been made toward understanding mechano--chemical coupling and fidelity control mechanisms of the polymerase elongation. The polymerases are regarded as molecular information motors during the elongation process. It requires a full spectrum of computational approaches from multiple time and length scales to understand the full polymerase functional cycle. We stay away from quantum mechanics based approaches to the polymerase catalysis due to abundant former surveys, while ad- dressing statistical physics modeling approaches along with all-atom molecular dynamics simulation studies. We organize this review around our own modeling and simulation practices on a single subunit T7 RNA polymerase, and summarize commensurate studies on structurally similar DNA polymerases as well. For multi-subunit RNA polymerases that have been actively studied in recent years, we leave systematical reviews of the simulation achievements to latest computational chemistry surveys, while covering only representative studies published very recently, including our own work modeling structure-based elongation kinetic of yeast RNA polymerase II. In the end, we briefly go through physical modeling on elongation pauses and backtracking activities of the multi-subunit RNAPs. We emphasize on the fluctuation and control mechanisms of the polymerase actions, highlight the non-equilibrium nature of the operation system, and try to build some perspectives toward understanding the polymerase impacts from the single molecule level to a genome-wide scale.
基金This work has been supported by the NSFC(Grant No.11534002)the NSAF(Grant No.U1930402 and Grant No.U1730449).
文摘We investigate the quantum dynamics of two defect centers in solids,which are coupled by vacuum-induced dipole-dipole interactions.When the interaction between defects and phonons is taken into account,the two coupled electron-phonon systems make up two equivalent multilevel atoms.By making Born-Markov and rotating wave approximations,we derive a master equation describing the dynamics of the coupled multilevel atoms.The results indicate the concepts of subradiant and superradiant states can be applied to these systems and the population transfer process presents different behaviors from those of the two dipolar-coupled two-level atoms due to the participation of phonons.
基金supported by the National Natural Science Foundation of China(52222407).
文摘Rechargeable magnesium-metal batteries(RMMBs)are promising next-generation secondary batteries;however,their development is inhibited by the low capacity and short cycle lifespan of cathodes.Although various strategies have been devised to enhance the Mg^(2+)migration kinetics and structural stability of cathodes,they fail to improve electronic conductivity,rendering the cathodes incompatible with magnesium-metal anodes.Herein,we propose a dual-defect engineering strategy,namely,the incorporation of Mg^(2+)pre-intercalation defect(P-Mgd)and oxygen defect(Od),to simultaneously improve the Mg^(2+)migration kinetics,structural stability,and electronic conductivity of the cathodes of RMMBs.Using lamellar V_(2)O_(5)·nH_(2)O as a demo cathode material,we prepare a cathode comprising Mg_(0.07)V_(2)O_(5)·1.4H_(2)O nanobelts composited with reduced graphene oxide(MVOH/rGO)with P-Mgd and Od.The Od enlarges interlayer spacing,accelerates Mg^(2+)migration kinetics,and prevents structural collapse,while the P-Mgd stabilizes the lamellar structure and increases electronic conductivity.Consequently,the MVOH/rGO cathode exhibits a high capacity of 197 mAh g^(−1),and the developed Mg foil//MVOH/rGO full cell demonstrates an incredible lifespan of 850 cycles at 0.1 A g^(−1),capable of powering a light-emitting diode.The proposed dual-defect engineering strategy provides new insights into developing high-durability,high-capacity cathodes,advancing the practical application of RMMBs,and other new secondary batteries.
基金supported by the Projects of Talents Recruitment of Guangdong University of Petrochemical Technology(No.2018rc14)Maoming City Science and Technology Plan Project(Nos.210427094551264 and 220415004552411).
文摘To investigate the influences of co-flowand counter-flowmodes of reactant flowarrangement on a proton exchange membrane fuel cell(PEMFC)during start-up,unsteady physical and mathematical models fully coupling the flow,heat,and electrochemical reactions in a PEMFC are established.The continuity equation and momentum equation are solved by handling pressure-velocity coupling using the SIMPLE algorithm.The electrochemical reaction rates in the catalyst layers(CLs)of the cathode and anode are calculated using the Butler-Volmer equation.The multiphase mixture model describes the multiphase transport process of gas mixtures and liquid water in the fuel cell.After validation,the influences of co-flow and counter-flow modes on the PEMFC performance are investigated,including the evolution of the current density,flow field,temperature field,and reactant concentration field during start-up,as well as the steady distribution of the current density,reactant concentration,andmembrane water content when the start-up stabilizes.Co-flow and counter-flow modes influence the current density distribution and temperature distribution.On the one hand,the co-flow mode accelerates the start-up process of the PEMFC and leads to a more evenly distributed current density than the counter-flow mode.On the other hand,the temperature difference between the inlet and outlet sections of the cell is up to 10.1℃ under the co-flow mode,much larger than the 5.0℃ observed in the counter-flow mode.Accordingly,the counter-flowmode results in a more evenly distributed temperature and a lower maximum temperature than the co-flow case.Therefore,in the flow field design of a PEMFC,the reactant flow arrangements can be considered to weigh between better heat management and higher current density distribution of the cell.
基金Project supported by the National Natural Science Foundation of China (Grant No.11834005)。
文摘The combination of non-Hermitian physics and Majorana fermions can give rise to new effects in quantum transport systems. In this work, we investigate the interplay of PT-symmetric complex potentials, Majorana tunneling and interdot tunneling in a non-Hermitian double quantum dots system. It is found that in the weak-coupling regime the Majorana tunneling has pronounced effects on the transport properties of such a system, manifested as splitting of the single peak into three and a reduced 1/4 peak in the transmission function. In the presence of the PT-symmetric complex potentials and interdot tunneling, the 1/4 central peak is robust against them, while the two side peaks are tuned by them. The interdot tunneling only induces asymmetry, instead of moving the conductance peak, due to the robustness of the Majorana modes. There is an exceptional point induced by the union of Majorana tunneling and interdot tunneling. With increased PT-symmetric complex potentials, the two side peaks will move towards each other. When the exceptional point is passed through, these two side peaks will disappear. In the strong-coupling regime, the Majorana fermion induces a 1/4 conductance dip instead of the three-peak structure. PT-symmetric complex potentials induce two conductance dips pinned at the exceptional point. These effects should be accessible in experiments.
基金supported by the National Natural Science Foundation of China(Grant Nos.11991060,52172136,12088101,12074029,and U2230402).
文摘Semiconductor devices are often operated at elevated temperatures that are well above zero Kelvin,which is the temperature in most first-principles density functional calculations.Computational approaches to com-puting and understanding the properties of semiconductors at finite temperatures are thus in critical demand.In this review,we discuss the recent progress in computationally assessing the electronic and phononic band structures of semiconductors at finite temperatures.As an emerging semiconductor with particularly strong temperature-induced renormalization of the electronic and phononic band structures,halide perovskites are used as a representative example to demonstrate how computational advances may help to understand the band struc-tures at elevated temperatures.Finally,we briefly illustrate the remaining computational challenges and outlook promising research directions that may help to guide future research in this field.
基金supported by the National Key Research and Development Program of China (Grant No.2022YFA1402700)the National Natural Science Foundation of China (Grant Nos.12174020,12088101,11974244,and U2230402)。
文摘The application of the eigenstate thermalization hypothesis to non-Hermitian quantum systems has become one of the most important topics in dissipative quantum chaos, recently giving rise to intense debates. The process of thermalization is intricate, involving many time-evolution trajectories in the reduced Hilbert space of the system. By considering two different expansion forms of the density matrices adopted in the biorthogonal and right-state time evolutions, we derive two versions of the Gorini–Kossakowski–Sudarshan–Lindblad(GKSL)master equations describing the non-Hermitian systems coupled to a bosonic heat bath in thermal equilibrium. By solving the equations, we identify a sufficient condition for thermalization under both time evolutions, resulting in Boltzmann biorthogonal and right-eigenstate statistics, respectively. This finding implies that the recently proposed biorthogonal random matrix theory needs an appropriate revision. Moreover, we exemplify the precise dynamics of thermalization and thermodynamic properties with test models.
基金supported by the National Natural Science Foundation of China(Grant Nos.52172136,12088101,11991060,and U2230402)。
文摘Materials for deep-ultraviolet(DUV)light emission are extremely rare,significantly limiting the development of efficient DUV light-emitting diodes.Here we report CsMg(I_(1−x)Br_(x))_(3) alloys as potential DUV light emitters.Based on rigorous first-principles hybrid functional calculations,we find that CsMgI_(3) has an indirect bandgap,while CsMgBr_(3) has a direct bandgap.Further,we employ a band unfolding technique for alloy supercell calculations to investigate the critical Br concentration in CsMg(I_(1−x)Br_(x))_(3) associated with the crossover from an indirect to a direct bandgap,which is found to be∼0.36.Thus,CsMg(I_(1−x)Br_(x))_(3) alloys with 0.366≤6≤1 cover a wide range of direct bandgap(4.38–5.37 eV;284–231 nm),falling well into the DUV regime.Our study will guide the development of efficient DUV light emitters.
