In the context of climate change,the acceleration of the global water cycle has led to the emergence of abrupt transitions between drought and flood events,presenting a new challenge for flood and drought disaster mit...In the context of climate change,the acceleration of the global water cycle has led to the emergence of abrupt transitions between drought and flood events,presenting a new challenge for flood and drought disaster mitigation.Abrupt transitions between drought and flood refer to a phenomenon in which an extreme drought event quickly shifts to an extreme flood event,or vice versa,within a relatively short time span.This phenomenon disrupts the traditional spatiotemporal distribution patterns of water-related disasters,reflecting not only the extreme unevenness in the distribution of water resources but also the rapid alternation of the water cycle's evolution(He et al.,2016).Moreover,due to its suddenness,extremity,and complexity,it poses severe threats to human societies and ecosystems.Scientifically addressing abrupt transitions between drought and flood has thus become a new challenge in flood and drought disaster prevention.展开更多
Active matter is a non-equilibrium condensed system consisting of self-propelled particles capable of converting stored or ambient energy into collective motion.Typical active matter systems include cytoskeleton biopo...Active matter is a non-equilibrium condensed system consisting of self-propelled particles capable of converting stored or ambient energy into collective motion.Typical active matter systems include cytoskeleton biopolymers,swimming bacteria,artificial swimmers,and animal herds.In contrast to wet active matter,dry active matter is an active system characterized by the absence of significant hydrodynamic interactions and conserved momentum.In dry active matter,the role of surrounding fluids is providing viscous friction at low Reynolds numbers and can be neglected at high Reynolds numbers.This review offers a comprehensive overview of recent experimental,computational,and theoretical advances in understanding phase transitions and critical phenomena in dry aligning active matter,including polar particles,self-propelled rods,active nematics,and their chiral counterparts.Various ways of determining phase transition points as well as non-equilibrium phenomena,such as collective motion,cluster formation,and creation and annihilation of topological defects are reviewed.展开更多
This letter presents a method for probing the attosecond time delay between two radiatively resonant transitions from Fano structures,which arise from interference between the extreme ultraviolet free induction decay(...This letter presents a method for probing the attosecond time delay between two radiatively resonant transitions from Fano structures,which arise from interference between the extreme ultraviolet free induction decay(XFID)emission and high-order harmonics.The ellipticity dependence of the Ne^(+)XFID yield confirms that the ionic excited-state populations originate from inelastic recollision between tunneling electrons and parent ions.Subsequent extraction of relative phases from Fano structures enables the determination of the time delay(~22 as)between the two decay pathways.This work provides an experimental approach to probe the attosecond time delay between different XFID channels and contributes to a deeper understanding of the tunneling-plusrescattering model in strong laser fields.展开更多
Phase transitions,as one of the most intriguing phenomena in nature,are divided into first-order phase transitions(FOPTs)and continuous ones in current classification.While the latter shows striking phenomena of scali...Phase transitions,as one of the most intriguing phenomena in nature,are divided into first-order phase transitions(FOPTs)and continuous ones in current classification.While the latter shows striking phenomena of scaling and universality,the former has recently also been demonstrated to exhibit scaling and universal behavior within a mesoscopic,coarse-grained Landau-Ginzburg theory.Here we apply this theory to a microscopic model-the paradigmatic Ising model,which undergoes FOPTs between two ordered phases below its critical temperature-and unambiguously demonstrate universal scaling behavior in such FOPTs.These results open the door for extending the theory to other microscopic FOPT systems and experimentally testing them to systematically uncover their scaling and universal behavior.展开更多
Mn_(3)Si_(2)Te_(6) is a ferrimagnetic nodal-line semiconductor with colossal angular magnetoresistance at ambient pressure.In this work,we investigated the effect of hydrostatic pressure on its electrical transport pr...Mn_(3)Si_(2)Te_(6) is a ferrimagnetic nodal-line semiconductor with colossal angular magnetoresistance at ambient pressure.In this work,we investigated the effect of hydrostatic pressure on its electrical transport properties,magnetic transition,and crystal structure by measuring resistivity,DC and AC magnetic susceptibility,and XRD under various pressures up to~20 GPa.Our results confirmed the occurrence of pressure-induced structural transition at P_(c)≈10–12 GPa accompanied by a concurrent drop of room-temperature resistance in Mn_(3)Si_(2)Te_(6).In the low-pressure phase at PP_(c),the sample exhibits a metallic behavior in the whole temperature range and its resistivity exhibits a kink anomaly at T_(M),characteristic of critical scattering around a magnetic transition.Recovery of the Raman spectrum upon decompression indicated that pressure-induced structural transition is reversible without amorphization under hydrostatic pressure conditions.Our present work not only resolves some existing controversial issues but also provides new insights into pressure-driven diverse behaviors of Mn_(3)Si_(2)Te_(6).展开更多
A longstanding discrepancy between theoretical predictions and experimental observations on the highpressurestructural transformations of lanthanum mononitride(LaN)has posed challenges for understandingthe behavior of...A longstanding discrepancy between theoretical predictions and experimental observations on the highpressurestructural transformations of lanthanum mononitride(LaN)has posed challenges for understandingthe behavior of heavy transition metal mononitrides.Here,we systematically investigate the structural evolutionof LaN under high pressure using first-principles calculations combined with angle-dispersive synchrotron X-raydiffraction,identifying the phase transition sequence and corresponding phase boundaries.Analyses of energetics,kinetic barriers,and lattice dynamics reveal distinct mechanisms driving these transitions.These results clarifythe structural stability of LaN and offer guidance for studying other heavy transition metal mononitrides withcomplex electronic behavior under extreme conditions.展开更多
We explored a distinct mechanism for matter creation via electron-positron pair production during bound-bound transitions in the deexcitation of muonic atoms.For ions with nuclear charges Z≥24,transitions from low-ly...We explored a distinct mechanism for matter creation via electron-positron pair production during bound-bound transitions in the deexcitation of muonic atoms.For ions with nuclear charges Z≥24,transitions from low-lying excited states to the 1s-muon state can lead to the production of electron-positron pairs.We show that the Breit interaction determines the transition probabilities for states with nonzero orbital momentum.We show that the pair production arises mainly from the decay of the 2p states.Thus,the Breit interaction governs electron-positron pair production in bound-bound muon transitions.This process offers a unique opportunity to explore quantum electrodynamics in strong fields,as well as a class of nonradiative transitions involving electron-positron pair production.展开更多
We investigate the localization and topological properties of the Haldane model under the influence of random flux and Anderson disorder. Our localization analysis reveals that random flux induces a transition from in...We investigate the localization and topological properties of the Haldane model under the influence of random flux and Anderson disorder. Our localization analysis reveals that random flux induces a transition from insulating to metallic states, while Anderson localization only arises under the modulation of Anderson disorder. By employing real-space topological invariant methods, we demonstrates that the system undergoes topological phase transitions under different disorder manipulations, whereas random flux modulation uniquely induces topological Anderson insulator phases, with the potential to generate states with opposite Chern numbers. These findings highlight the distinct roles of disorder in shaping the interplay between topology and localization, providing insights into stabilizing topological states and designing robust topological quantum materials.展开更多
We study the average rate of change of energy of two accelerated entangled atoms coupled to electromagnetic fields in the presence of a reflecting boundary,which according to the Dalibard,Dupont-Roc and Cohen-Tannoudj...We study the average rate of change of energy of two accelerated entangled atoms coupled to electromagnetic fields in the presence of a reflecting boundary,which according to the Dalibard,Dupont-Roc and Cohen-Tannoudji formalism is only attributed to the contribution of the radiative reaction of atoms.When the boundary is present,this result can be expressed as the sum of the free-space result and the boundary-induced modifications,and it generally depends on the two-atom initial state,the orientations of atomic dipole moments,as well as the relative scales among atom-boundary distance,interatomic separation and the inverse of atomic acceleration.When the two atoms are vertically aligned and one atom is very close to the boundary,we find that the terms only related to the closer atom are zero for the symmetric state but double the free-space counterpart for the antisymmetric state,if the atom is polarizable parallel to the boundary.However,for the atom polarizable vertically to the boundary,these terms vanish for the antisymmetric state but are twice the free-space counterpart for the symmetric state.Moreover,the terms related to the farther atom exhibit obviously oscillatory behavior,and the terms related to both atoms are vanishing unless the dipole moments of two atoms both have their components vertical to the boundary.When the two atoms are aligned parallel to and very close to the boundary,the terms related to one atom are interatomicseparation-independent and only influenced by the atomic dipole moments.The terms related to both atoms are actually consistent with the counterpart in the vertical-alignment case.In addition,when the two atoms are polarizable along the direction parallel to the boundary,the average rate of change of energy of two parallel-aligned and symmetric entangled atoms vanishes as if the two atoms were a closed system.展开更多
Mg_(2)V_(2)O_(7)is the most promising candidate for low-temperature co-fired ceramic(LTCC)multilayer devices.Selecting the appropriate precursors strongly requires reliable thermodynamic properties to be defined accur...Mg_(2)V_(2)O_(7)is the most promising candidate for low-temperature co-fired ceramic(LTCC)multilayer devices.Selecting the appropriate precursors strongly requires reliable thermodynamic properties to be defined accurately.In this study,the structural parameters of the Mg_(2)V_(2)O_(7)at ambient temperature indicate that it is crystallized in space group of P2_(1)/c.Notably,Mg_(2)V_(2)O_(7)has low lattice thermal conductivity(k_(L))of 4.77,5.12,and 4.52 W/m K,along the a,b,and c axes,respectively,which originates from the large phonon scattering rate and low phonon group velocity.The α-Mg_(2)V_(2)O_(7)←→β-Mg_(2)V_(2)O_(7) and β-Mg_(2)V_(2)O_(7)←→γ-Mg_(2)V_(2)O_(7)polymorphic transitions occur at 743℃and 908℃with enthalpy change of 1.82±0.04 kJ/mol and 1.51±0.04 kJ/mol,respectively.The endothermic effect at 1083℃ with an enthalpy change of 26.54±0.26 kJ/mol is related to the congruent melting of γ-Mg_(2)V_(2)O_(7).In addition,the molar heat capacity of Mg_(2)V_(2)O_(7) was measured utilizing drop calorimetry at high temperatures.The measured thermodynamic properties were then applied to select precursors for preparing Mg_(2)V_(2)O_(7)via a solid-state reaction,indicating that the V_(2)O_5 and Mg(OH)_(2) precursors are strongly recommended due to their thermodynamic superiority.展开更多
Understanding the occurrence and characteristics of dry and wet events is crucial for effective disaster prevention,resource management,and risk reduction in vulnerable regions.This study analyzed the spatiotemporal p...Understanding the occurrence and characteristics of dry and wet events is crucial for effective disaster prevention,resource management,and risk reduction in vulnerable regions.This study analyzed the spatiotemporal patterns of dry-wet events and their transition characteristics in Uttar Pradesh,India.The standardized precipitation evapotranspiration index(SPEI)at a monthly timescale was utilized to identify hotspot regions vulnerable to concurrent and frequent dry and wet events and their transitions.The severity,duration,and intensity of dry and wet events were characterized with the run theory over SPEI time series data from 18 synoptic stations in Uttar Pradesh over 48 years(1971-2018),sourced from the Indian Institute of Tropical Meteorology and the India Meteorological Department.Multiple assessment methods were utilized to examine the interaction of these extreme events,considering characteristics such as wet-dry ratio,average transition time,and rapid transition times from wet to dry events and from dry to wet events.Average wet durations ranged from 1.27 to 1.58 months,and average dry durations ranged from 1.29 to 1.82 months.Rapid transition times from dry to wet events ranged from 2.5 to 4.1 months,and those for wet-to-dry events ranged from 2.1 to 5.3 months.The eastern region experienced a significantly high number of dry events,while the western and Bundelkhand regions experienced more intense dry events.In contrast,the eastern region had intense wet events.This research on the occurrence of dry-wet events and their transitions can provide valuable insights for government decision-making and disaster prevention and reduction efforts.展开更多
The phase transition among different solid forms of active pharmaceutical ingredients can significantly influence their physicochemical properties,potentially leading to clinical safety risks.However,phase transition ...The phase transition among different solid forms of active pharmaceutical ingredients can significantly influence their physicochemical properties,potentially leading to clinical safety risks.However,phase transition mechanisms remain under explored,especially in multi-component drugs.Here we report a novel ciprofloxacin-diclofenac salt system and investigate phase transitions among its anhydrate,dihydrate,and methanol solvate forms.The study focused on the influence of water activity and solvent vapor conditions,elucidating the role of vip molecules in driving these transitions.These findings offer new insights into polymorphic phase transitions,advancing our understanding of stability and performance in pharmaceutical formulations.展开更多
Kibble-Zurek scaling is the scaling of the density of topological defects formed via the Kibble-Zurek mechanism with respect to the rate at which a system is cooled across a continuous phase transition.Recently,the de...Kibble-Zurek scaling is the scaling of the density of topological defects formed via the Kibble-Zurek mechanism with respect to the rate at which a system is cooled across a continuous phase transition.Recently,the density of the topological defects formed via the Kibble-Zurek mechanism was estimated for a system cooled through a first-order phase transition rather than conventional continuous transitions.Here we address the problem of whether such defects generated across a first-order phase transition exhibit Kibble-Zurek scaling similar to the case in continuous phase transitions.We show that any possible Kibble-Zurek scaling for the topological defects can only be a very rough approximation due to an intrinsic field responsible for the scaling.However,complete universal scaling for other properties does exist.展开更多
Based on the principles of thermodynamics, we elucidate the fundamental reasons behind the hysteresis of spontaneous polarization in ferroelectric materials during heating and cooling processes. By utilizing the effec...Based on the principles of thermodynamics, we elucidate the fundamental reasons behind the hysteresis of spontaneous polarization in ferroelectric materials during heating and cooling processes. By utilizing the effective Hamiltonian method in conjuction with the phase-field model, we have successfully reproduced the thermal hysteresis observed in ferroelectric materials during phase transitions. The computational results regarding the electrocaloric effect from these two different computational scales closely align with experimental measurements. Furthermore, we analyze how the first-order ferroelectric phase transition gradually diminishes with an increasing applied electric field, exhibiting characteristics of second-order-like phase transition. By employing the characteristic parameters of thermal hysteresis, we have established a pathway for calculations across different computational scales, thereby providing theoretical support for further investigations into the properties of ferroelectric materials through concurrent multiscale simulations.展开更多
We propose an eigen microstate approach(EMA)for analyzing quantum phase transitions in quantum many-body systems,introducing a novel framework that does not require prior knowledge of an order parameter.Using the tran...We propose an eigen microstate approach(EMA)for analyzing quantum phase transitions in quantum many-body systems,introducing a novel framework that does not require prior knowledge of an order parameter.Using the transversefield Ising model(TFIM)as a case study,we demonstrate the effectiveness of EMA by identifying key features of the phase transition through the scaling behavior of eigenvalues and the structure of associated eigen microstates.Our results reveal substantial changes in the ground state of the TFIM as it undergoes a phase transition,as reflected in the behavior of specific componentsξ_(i)^((k))within the eigen microstates.This method is expected to be applicable to other quantum systems where predefining an order parameter is challenging.展开更多
Energy security is a crucial aspect of modern societies,as it directly impacts the availability,accessibility,and reliability of energy sources.The reliance on natural resources and geopolitical factors in shaping ene...Energy security is a crucial aspect of modern societies,as it directly impacts the availability,accessibility,and reliability of energy sources.The reliance on natural resources and geopolitical factors in shaping energy security has gained significant attention in recent years.Natural resources and geopolitical risk are examined in 38 countries at risk of geopolitical conflict between 1990 and 2021 by examining CO_(2) emissions,renewable energy consumption,and foreign direct investment as controlling variables.The long-run analysis conducted in this study focused on slope heterogeneity,Westerlund cointegration,and dynamic panel data estimation.The findings indicated that the energy security index is positively associated with various determinants,including natural resources,geopolitical risk,CO_(2) emissions,and renewable energy consumption.However,foreign direct investment was found to be negatively associated with the energy security index among the selected 38 geopolitical risk countries.The role of natural resources and geopolitical risk in energy security cannot be overlooked.Natural resources provide the raw materials for generating electricity and powering our societies,while geopolitical risks can disrupt energy supply chains and threaten stability.Achieving sustainable energy security requires a comprehensive approach that addresses both aspects of energy provision.Transitioning to renewable energy sources,improving energy efficiency,diversifying energy supplies,promoting international cooperation,and conserving natural resources are essential steps towards a more sustainable and resilient energy future.展开更多
The rare earth(RE)-transition metal(TM)based compounds have emerged as one of the best candi-dates for the application in eco-friendly and effective cooling technology due to their outstanding cryogenic magnetocaloric...The rare earth(RE)-transition metal(TM)based compounds have emerged as one of the best candi-dates for the application in eco-friendly and effective cooling technology due to their outstanding cryogenic magnetocaloric performances.In this work,three RE-TM germanides RE_(3)Co_(2)Ge_(4)(RE=Gd,Tb and Dy)were synthesized and characterized,aiming to investigating their structural,magnetic and magnetocaloric properties.These compounds crystallize in the Tb_(3)Co_(2)Ge_(4)-type monoclinic structure(space group C2/m,Z=2).Two successive ferromagnetic transitions are observed with T_(c) of 31 and 135 K for Gd_(3)Co_(2)Ge_(4),ferromagnetic and spin reorientation transitions are observed with Tc of 24 K and T_(s) of 19 K for Dy_(3)Co_(2)Ge_(4),all of which are second ordered.In contrast,Tb_(3)Co_(2)Ge_(4)exhibits a second order antiferromagnetic transition with T_(n) of 36 K,accompanied with a spin reorientation transition with T_(s) of 17 K.Furthermore,the ferromagnetic ground state for Gd_(3)Co_(2)Ge_(4)is also confirmed by the first-principles calculations.Significant cryogenic magnetocaloric performances are observed in these compounds,.The determined maximum magnetic entropy change(-ΔS_(M)^(max))under a magnetic field change(△H)of 0-7 T are 10.7,5.3 and 11.6 J/(kg·K)for Gd_(3)Co_(2)Ge_(4),Tb_(3)Co_(2)Ge_(4)and Dy_(3)Co_(2)Ge_(4),respectively.Our results suggest that Gd_(3)Co_(2)Ge_(4)and Dy_(3)Co_(2)Ge_(4)compounds are attractive candidates for cryogenic magnetic refrigeration applications.展开更多
As a promising anode material for magnesium ion rechargeable batteries,magnesium metavanadate(MgV_(2)O_(6))has attracted considerable research interest in recent years.A MgV_(2)O_(6)sample was synthesized via a facile...As a promising anode material for magnesium ion rechargeable batteries,magnesium metavanadate(MgV_(2)O_(6))has attracted considerable research interest in recent years.A MgV_(2)O_(6)sample was synthesized via a facile solid-state reaction by multistep-firing stoichiometric mixtures of MgO and V2O5 powder under an air atmosphere.The solid-state phase transition fromα-MgV_(2)O_(6)toβ-MgV_(2)O_(6)occurred at 841 K and the enthalpy change was 4.37±0.04 kJ/mol.The endothermic effect at 1014 K and the enthalpy change was 26.54±0.26 kJ/mol,which is related to the incongruent melting ofβ-MgV_(2)O_(6).In situ XRD was performed to investigate phase transition of the as-prepared MgV_(2)O_(6)at high temperatures.The cell parameters obtained by Rietveld refinement indicated that it crystallizes in a monoclinic system with the C2/m space group,and the lattice parameters of a=9.280 A°,b=3.501 A°,c=6.731 A°,β=111.76°.The solid-state phase transition fromα-MgV_(2)O_(6)toβ-MgV_(2)O_(6)was further studied by thermal kinetics,indicating that this process is controlled first by a fibril-like mechanism and then by a spherulitic-type mechanism with an increasing heating rate.Additionally,the enthalpy change of MgV_(2)O_(6)at high temperatures was measured utilizing the drop calorimetry,heat capacity was calculated and given as:Cp=208.3+0.03583T-4809000T^(−2)(298-923 K)(J mol^(−1)K^(−1)),the high-temperature heat capacity can be used to calculate Gibbs free energy of MgV_(2)O_(6)at high temperatures.展开更多
Multiple quantum coherences are often employed to describe quantum many-body dynamics in nuclear spin systems and recently,to characterize quantum phase transitions in trapped ions.Here we investigate the multiple-qua...Multiple quantum coherences are often employed to describe quantum many-body dynamics in nuclear spin systems and recently,to characterize quantum phase transitions in trapped ions.Here we investigate the multiple-quantum-coherence dynamics of a spin-1 Bose–Einstein condensate.By adjusting the quadratic Zeeman shift,the condensate exhibits three quantum phases.Our numerical results show that the spectrum of multiple quantum coherence does indeed catch the quantum critical points.More importantly,with only a few low-order multiple quantum coherences,the spin-1 condensate exhibits rich signals of the many-body dynamics,beyond conventional observables.The experimental implementation of such multiple quantum coherence protocol is also discussed.展开更多
The ecological function of land use is the basis for developing an ecological civilization and realizing sustainable development.This paper may help guide the coordination of economic development and ecological develo...The ecological function of land use is the basis for developing an ecological civilization and realizing sustainable development.This paper may help guide the coordination of economic development and ecological development in China’s coastal border areas.Based on theoretical analysis,this paper studies the spatiotemporal evolution of the functional spaces and the ecological function transitions of land use in the Beibu Gulf Economic Zone(BGEZ)by analyzing patterns,processes,and factors by applying eco-environmental quality index,grid subdivision,kriging interpolation,barycenter model,and Geodetector.This paper constructs a theoretical framework of ecological function transitions of land use based on the research idea of“system-pattern-process-factor”,and carries out empirical research.Some conclusions can be drawn as follows:(1)The ecological space in the BGEZ has continuously decreased,converting mainly into agricultural production space and industrial-mining production space.The production space has expanded slowly.The area of living space in the BGEZ has increased rapidly.(2)The ecological function of land use in the BGEZ has continued to weaken,especially in the southern part of the BGEZ.The“high-sub-high”quality zones of ecological function are retreating to the north.(3)There were more deterioration transition areas than optimization transition areas of ecological function in the BGEZ.The former were mostly located in the central and southern urbanized areas of the BGEZ,whereas the latter were mostly located in the edge zones of district and county units.(4)As for the driving factors of the deterioration transitions of land use ecological function in the BGEZ,the significant trend of“de-ecologization”of the land cover/land use structure was the dominant driving factor;the interactions among the“natural-socioeconomic-managerial”systems were the main recessive factor.The natural system played a fundamental role,and the driving force of natural factors was the strongest.The industrialization,urbanization,and GDP increment in the socioeconomic system and the policy positioning of development intensity in the managerial system played a significant role.The interactions among natural factors,road construction,and industrial non-agricultural transformation had a“fuze”effect on stimulating driving forces.展开更多
基金supported by the National Key Research and Development Program of China(Grant No.2023YFC3209800)the National Natural Science Foundation of China(Grant No.52279011).
文摘In the context of climate change,the acceleration of the global water cycle has led to the emergence of abrupt transitions between drought and flood events,presenting a new challenge for flood and drought disaster mitigation.Abrupt transitions between drought and flood refer to a phenomenon in which an extreme drought event quickly shifts to an extreme flood event,or vice versa,within a relatively short time span.This phenomenon disrupts the traditional spatiotemporal distribution patterns of water-related disasters,reflecting not only the extreme unevenness in the distribution of water resources but also the rapid alternation of the water cycle's evolution(He et al.,2016).Moreover,due to its suddenness,extremity,and complexity,it poses severe threats to human societies and ecosystems.Scientifically addressing abrupt transitions between drought and flood has thus become a new challenge in flood and drought disaster prevention.
基金granted by the National Natural Science Foundation of China(No.12047503)Wenzhou Institute,University of Chinese Academy of Sciences(No.WIUCASQD2023009)。
文摘Active matter is a non-equilibrium condensed system consisting of self-propelled particles capable of converting stored or ambient energy into collective motion.Typical active matter systems include cytoskeleton biopolymers,swimming bacteria,artificial swimmers,and animal herds.In contrast to wet active matter,dry active matter is an active system characterized by the absence of significant hydrodynamic interactions and conserved momentum.In dry active matter,the role of surrounding fluids is providing viscous friction at low Reynolds numbers and can be neglected at high Reynolds numbers.This review offers a comprehensive overview of recent experimental,computational,and theoretical advances in understanding phase transitions and critical phenomena in dry aligning active matter,including polar particles,self-propelled rods,active nematics,and their chiral counterparts.Various ways of determining phase transition points as well as non-equilibrium phenomena,such as collective motion,cluster formation,and creation and annihilation of topological defects are reviewed.
基金supported by the National Natural Science Foundation of China(Grant Nos.12234020,12474281,12450403,and 12274461)the Science and Technology Innovation Program of Hunan Province(Grant No.2022RC1193).
文摘This letter presents a method for probing the attosecond time delay between two radiatively resonant transitions from Fano structures,which arise from interference between the extreme ultraviolet free induction decay(XFID)emission and high-order harmonics.The ellipticity dependence of the Ne^(+)XFID yield confirms that the ionic excited-state populations originate from inelastic recollision between tunneling electrons and parent ions.Subsequent extraction of relative phases from Fano structures enables the determination of the time delay(~22 as)between the two decay pathways.This work provides an experimental approach to probe the attosecond time delay between different XFID channels and contributes to a deeper understanding of the tunneling-plusrescattering model in strong laser fields.
基金supported by the National Natural Science Foundation of China(Grant No.12175316).
文摘Phase transitions,as one of the most intriguing phenomena in nature,are divided into first-order phase transitions(FOPTs)and continuous ones in current classification.While the latter shows striking phenomena of scaling and universality,the former has recently also been demonstrated to exhibit scaling and universal behavior within a mesoscopic,coarse-grained Landau-Ginzburg theory.Here we apply this theory to a microscopic model-the paradigmatic Ising model,which undergoes FOPTs between two ordered phases below its critical temperature-and unambiguously demonstrate universal scaling behavior in such FOPTs.These results open the door for extending the theory to other microscopic FOPT systems and experimentally testing them to systematically uncover their scaling and universal behavior.
基金supported by the National Key R&D Program of China (Grant Nos. 2023YFA1406100, 2022YFA1403900, 2024YFA1408400, 2021YFA1400200, 2022YFA1403800, and 2023YFA1406500)the National Natural Science Foundation of China (Grant Nos. 12174424, 12025408, 11921004, U22A6005, and 12274459)+1 种基金the Youth Innovation Promotion Association of Chinese Academy of Sciences (Grant No. 2023007)the Chinese Academy of Sciences President’s International Fellowship Initiative (Grant No. 2024PG0003)。
文摘Mn_(3)Si_(2)Te_(6) is a ferrimagnetic nodal-line semiconductor with colossal angular magnetoresistance at ambient pressure.In this work,we investigated the effect of hydrostatic pressure on its electrical transport properties,magnetic transition,and crystal structure by measuring resistivity,DC and AC magnetic susceptibility,and XRD under various pressures up to~20 GPa.Our results confirmed the occurrence of pressure-induced structural transition at P_(c)≈10–12 GPa accompanied by a concurrent drop of room-temperature resistance in Mn_(3)Si_(2)Te_(6).In the low-pressure phase at PP_(c),the sample exhibits a metallic behavior in the whole temperature range and its resistivity exhibits a kink anomaly at T_(M),characteristic of critical scattering around a magnetic transition.Recovery of the Raman spectrum upon decompression indicated that pressure-induced structural transition is reversible without amorphization under hydrostatic pressure conditions.Our present work not only resolves some existing controversial issues but also provides new insights into pressure-driven diverse behaviors of Mn_(3)Si_(2)Te_(6).
基金supported by the Natural Science Foundation of China(Grant Nos.T2325013,12474004,and 52288102)the National Key Research and Development Program of China(Grant No.2021YFA1400503)the Program for Jilin University Science and Technology Innovative Research Team。
文摘A longstanding discrepancy between theoretical predictions and experimental observations on the highpressurestructural transformations of lanthanum mononitride(LaN)has posed challenges for understandingthe behavior of heavy transition metal mononitrides.Here,we systematically investigate the structural evolutionof LaN under high pressure using first-principles calculations combined with angle-dispersive synchrotron X-raydiffraction,identifying the phase transition sequence and corresponding phase boundaries.Analyses of energetics,kinetic barriers,and lattice dynamics reveal distinct mechanisms driving these transitions.These results clarifythe structural stability of LaN and offer guidance for studying other heavy transition metal mononitrides withcomplex electronic behavior under extreme conditions.
基金supported by the National Key Research and Development Program of China(Grant No.2022YFA1602501)the National Natural Science Foundation of China(Grant No.12011530060)+1 种基金supported solely by the Russian Science Foundation(Grant No.22-12-00043)supported by the Chinese Academy of Sciences(CAS)Presidents International Fellowship Initiative(PIFI)(Grant Nos.2018VMB0016 and 2022VMC0002),respectively。
文摘We explored a distinct mechanism for matter creation via electron-positron pair production during bound-bound transitions in the deexcitation of muonic atoms.For ions with nuclear charges Z≥24,transitions from low-lying excited states to the 1s-muon state can lead to the production of electron-positron pairs.We show that the Breit interaction determines the transition probabilities for states with nonzero orbital momentum.We show that the pair production arises mainly from the decay of the 2p states.Thus,the Breit interaction governs electron-positron pair production in bound-bound muon transitions.This process offers a unique opportunity to explore quantum electrodynamics in strong fields,as well as a class of nonradiative transitions involving electron-positron pair production.
基金Project supported by the National Key Research and Development Program of China (Grant Nos. 2021YFA1400900, 2021YFA0718300, and 2021YFA1402100)the National Natural Science Foundation of China (Grant Nos. 12174461, 12234012, 12334012, and 52327808)。
文摘We investigate the localization and topological properties of the Haldane model under the influence of random flux and Anderson disorder. Our localization analysis reveals that random flux induces a transition from insulating to metallic states, while Anderson localization only arises under the modulation of Anderson disorder. By employing real-space topological invariant methods, we demonstrates that the system undergoes topological phase transitions under different disorder manipulations, whereas random flux modulation uniquely induces topological Anderson insulator phases, with the potential to generate states with opposite Chern numbers. These findings highlight the distinct roles of disorder in shaping the interplay between topology and localization, providing insights into stabilizing topological states and designing robust topological quantum materials.
基金supported in part by the NSFC under Grant Nos.12047551 and 12105061the Graduate Innovation Project of Shanxi Normal University under Grant No.2023XSY041。
文摘We study the average rate of change of energy of two accelerated entangled atoms coupled to electromagnetic fields in the presence of a reflecting boundary,which according to the Dalibard,Dupont-Roc and Cohen-Tannoudji formalism is only attributed to the contribution of the radiative reaction of atoms.When the boundary is present,this result can be expressed as the sum of the free-space result and the boundary-induced modifications,and it generally depends on the two-atom initial state,the orientations of atomic dipole moments,as well as the relative scales among atom-boundary distance,interatomic separation and the inverse of atomic acceleration.When the two atoms are vertically aligned and one atom is very close to the boundary,we find that the terms only related to the closer atom are zero for the symmetric state but double the free-space counterpart for the antisymmetric state,if the atom is polarizable parallel to the boundary.However,for the atom polarizable vertically to the boundary,these terms vanish for the antisymmetric state but are twice the free-space counterpart for the symmetric state.Moreover,the terms related to the farther atom exhibit obviously oscillatory behavior,and the terms related to both atoms are vanishing unless the dipole moments of two atoms both have their components vertical to the boundary.When the two atoms are aligned parallel to and very close to the boundary,the terms related to one atom are interatomicseparation-independent and only influenced by the atomic dipole moments.The terms related to both atoms are actually consistent with the counterpart in the vertical-alignment case.In addition,when the two atoms are polarizable along the direction parallel to the boundary,the average rate of change of energy of two parallel-aligned and symmetric entangled atoms vanishes as if the two atoms were a closed system.
基金supported by the National Key Research and Development Program of China(No.2022YFC3901001-1)the National Natural Science Foundation of China(Grant No.U1902217)financial support from the Chinese Scholarship Council(CSC No.202106050084)。
文摘Mg_(2)V_(2)O_(7)is the most promising candidate for low-temperature co-fired ceramic(LTCC)multilayer devices.Selecting the appropriate precursors strongly requires reliable thermodynamic properties to be defined accurately.In this study,the structural parameters of the Mg_(2)V_(2)O_(7)at ambient temperature indicate that it is crystallized in space group of P2_(1)/c.Notably,Mg_(2)V_(2)O_(7)has low lattice thermal conductivity(k_(L))of 4.77,5.12,and 4.52 W/m K,along the a,b,and c axes,respectively,which originates from the large phonon scattering rate and low phonon group velocity.The α-Mg_(2)V_(2)O_(7)←→β-Mg_(2)V_(2)O_(7) and β-Mg_(2)V_(2)O_(7)←→γ-Mg_(2)V_(2)O_(7)polymorphic transitions occur at 743℃and 908℃with enthalpy change of 1.82±0.04 kJ/mol and 1.51±0.04 kJ/mol,respectively.The endothermic effect at 1083℃ with an enthalpy change of 26.54±0.26 kJ/mol is related to the congruent melting of γ-Mg_(2)V_(2)O_(7).In addition,the molar heat capacity of Mg_(2)V_(2)O_(7) was measured utilizing drop calorimetry at high temperatures.The measured thermodynamic properties were then applied to select precursors for preparing Mg_(2)V_(2)O_(7)via a solid-state reaction,indicating that the V_(2)O_5 and Mg(OH)_(2) precursors are strongly recommended due to their thermodynamic superiority.
文摘Understanding the occurrence and characteristics of dry and wet events is crucial for effective disaster prevention,resource management,and risk reduction in vulnerable regions.This study analyzed the spatiotemporal patterns of dry-wet events and their transition characteristics in Uttar Pradesh,India.The standardized precipitation evapotranspiration index(SPEI)at a monthly timescale was utilized to identify hotspot regions vulnerable to concurrent and frequent dry and wet events and their transitions.The severity,duration,and intensity of dry and wet events were characterized with the run theory over SPEI time series data from 18 synoptic stations in Uttar Pradesh over 48 years(1971-2018),sourced from the Indian Institute of Tropical Meteorology and the India Meteorological Department.Multiple assessment methods were utilized to examine the interaction of these extreme events,considering characteristics such as wet-dry ratio,average transition time,and rapid transition times from wet to dry events and from dry to wet events.Average wet durations ranged from 1.27 to 1.58 months,and average dry durations ranged from 1.29 to 1.82 months.Rapid transition times from dry to wet events ranged from 2.5 to 4.1 months,and those for wet-to-dry events ranged from 2.1 to 5.3 months.The eastern region experienced a significantly high number of dry events,while the western and Bundelkhand regions experienced more intense dry events.In contrast,the eastern region had intense wet events.This research on the occurrence of dry-wet events and their transitions can provide valuable insights for government decision-making and disaster prevention and reduction efforts.
基金supported by the Young Scientists Promotion Fund of Natural Science Foundation of Guangdong Province(No.2023A1515030128)Natural Science Foundation of Guangdong Province(No.2024A1515011590)+1 种基金National Natural Science Foundation of China(No.81703438)CAMS Innovation Fund for Medical Sciences(No.2022-I2M-1-015).
文摘The phase transition among different solid forms of active pharmaceutical ingredients can significantly influence their physicochemical properties,potentially leading to clinical safety risks.However,phase transition mechanisms remain under explored,especially in multi-component drugs.Here we report a novel ciprofloxacin-diclofenac salt system and investigate phase transitions among its anhydrate,dihydrate,and methanol solvate forms.The study focused on the influence of water activity and solvent vapor conditions,elucidating the role of vip molecules in driving these transitions.These findings offer new insights into polymorphic phase transitions,advancing our understanding of stability and performance in pharmaceutical formulations.
基金supported by the National Natural Science Foundation of China(Grant No.12175316)。
文摘Kibble-Zurek scaling is the scaling of the density of topological defects formed via the Kibble-Zurek mechanism with respect to the rate at which a system is cooled across a continuous phase transition.Recently,the density of the topological defects formed via the Kibble-Zurek mechanism was estimated for a system cooled through a first-order phase transition rather than conventional continuous transitions.Here we address the problem of whether such defects generated across a first-order phase transition exhibit Kibble-Zurek scaling similar to the case in continuous phase transitions.We show that any possible Kibble-Zurek scaling for the topological defects can only be a very rough approximation due to an intrinsic field responsible for the scaling.However,complete universal scaling for other properties does exist.
基金Project supported financially by the National Natural Science Foundation of China (Grant No. 52372100)the National Key Research and Development Program of China (Grant No. 2019YFA0307900)。
文摘Based on the principles of thermodynamics, we elucidate the fundamental reasons behind the hysteresis of spontaneous polarization in ferroelectric materials during heating and cooling processes. By utilizing the effective Hamiltonian method in conjuction with the phase-field model, we have successfully reproduced the thermal hysteresis observed in ferroelectric materials during phase transitions. The computational results regarding the electrocaloric effect from these two different computational scales closely align with experimental measurements. Furthermore, we analyze how the first-order ferroelectric phase transition gradually diminishes with an increasing applied electric field, exhibiting characteristics of second-order-like phase transition. By employing the characteristic parameters of thermal hysteresis, we have established a pathway for calculations across different computational scales, thereby providing theoretical support for further investigations into the properties of ferroelectric materials through concurrent multiscale simulations.
基金supported by the National Natural Science Foundation of China(Grant Nos.12475033,12135003,12174194,and 12405032)the National Key Research and Development Program of China(Grant No.2023YFE0109000)+1 种基金supported by the Fundamental Research Funds for the Central Universitiessupport from the China Postdoctoral Science Foundation(Grant No.2023M730299).
文摘We propose an eigen microstate approach(EMA)for analyzing quantum phase transitions in quantum many-body systems,introducing a novel framework that does not require prior knowledge of an order parameter.Using the transversefield Ising model(TFIM)as a case study,we demonstrate the effectiveness of EMA by identifying key features of the phase transition through the scaling behavior of eigenvalues and the structure of associated eigen microstates.Our results reveal substantial changes in the ground state of the TFIM as it undergoes a phase transition,as reflected in the behavior of specific componentsξ_(i)^((k))within the eigen microstates.This method is expected to be applicable to other quantum systems where predefining an order parameter is challenging.
基金funded by a grant from the Interdisciplinary Research Institute in New Finance and Economics,Hubei University of Economics(No.JXZD202403).
文摘Energy security is a crucial aspect of modern societies,as it directly impacts the availability,accessibility,and reliability of energy sources.The reliance on natural resources and geopolitical factors in shaping energy security has gained significant attention in recent years.Natural resources and geopolitical risk are examined in 38 countries at risk of geopolitical conflict between 1990 and 2021 by examining CO_(2) emissions,renewable energy consumption,and foreign direct investment as controlling variables.The long-run analysis conducted in this study focused on slope heterogeneity,Westerlund cointegration,and dynamic panel data estimation.The findings indicated that the energy security index is positively associated with various determinants,including natural resources,geopolitical risk,CO_(2) emissions,and renewable energy consumption.However,foreign direct investment was found to be negatively associated with the energy security index among the selected 38 geopolitical risk countries.The role of natural resources and geopolitical risk in energy security cannot be overlooked.Natural resources provide the raw materials for generating electricity and powering our societies,while geopolitical risks can disrupt energy supply chains and threaten stability.Achieving sustainable energy security requires a comprehensive approach that addresses both aspects of energy provision.Transitioning to renewable energy sources,improving energy efficiency,diversifying energy supplies,promoting international cooperation,and conserving natural resources are essential steps towards a more sustainable and resilient energy future.
基金the Science and Technology Development Fund,Macao SAR,China(006/2022/ALC).
文摘The rare earth(RE)-transition metal(TM)based compounds have emerged as one of the best candi-dates for the application in eco-friendly and effective cooling technology due to their outstanding cryogenic magnetocaloric performances.In this work,three RE-TM germanides RE_(3)Co_(2)Ge_(4)(RE=Gd,Tb and Dy)were synthesized and characterized,aiming to investigating their structural,magnetic and magnetocaloric properties.These compounds crystallize in the Tb_(3)Co_(2)Ge_(4)-type monoclinic structure(space group C2/m,Z=2).Two successive ferromagnetic transitions are observed with T_(c) of 31 and 135 K for Gd_(3)Co_(2)Ge_(4),ferromagnetic and spin reorientation transitions are observed with Tc of 24 K and T_(s) of 19 K for Dy_(3)Co_(2)Ge_(4),all of which are second ordered.In contrast,Tb_(3)Co_(2)Ge_(4)exhibits a second order antiferromagnetic transition with T_(n) of 36 K,accompanied with a spin reorientation transition with T_(s) of 17 K.Furthermore,the ferromagnetic ground state for Gd_(3)Co_(2)Ge_(4)is also confirmed by the first-principles calculations.Significant cryogenic magnetocaloric performances are observed in these compounds,.The determined maximum magnetic entropy change(-ΔS_(M)^(max))under a magnetic field change(△H)of 0-7 T are 10.7,5.3 and 11.6 J/(kg·K)for Gd_(3)Co_(2)Ge_(4),Tb_(3)Co_(2)Ge_(4)and Dy_(3)Co_(2)Ge_(4),respectively.Our results suggest that Gd_(3)Co_(2)Ge_(4)and Dy_(3)Co_(2)Ge_(4)compounds are attractive candidates for cryogenic magnetic refrigeration applications.
基金supported by the National Key R&D Program of China(2018YFC1900500)the Graduate Scientific Research and Innovation Foundation of Chongqing,China(Grant No.CYB20002).
文摘As a promising anode material for magnesium ion rechargeable batteries,magnesium metavanadate(MgV_(2)O_(6))has attracted considerable research interest in recent years.A MgV_(2)O_(6)sample was synthesized via a facile solid-state reaction by multistep-firing stoichiometric mixtures of MgO and V2O5 powder under an air atmosphere.The solid-state phase transition fromα-MgV_(2)O_(6)toβ-MgV_(2)O_(6)occurred at 841 K and the enthalpy change was 4.37±0.04 kJ/mol.The endothermic effect at 1014 K and the enthalpy change was 26.54±0.26 kJ/mol,which is related to the incongruent melting ofβ-MgV_(2)O_(6).In situ XRD was performed to investigate phase transition of the as-prepared MgV_(2)O_(6)at high temperatures.The cell parameters obtained by Rietveld refinement indicated that it crystallizes in a monoclinic system with the C2/m space group,and the lattice parameters of a=9.280 A°,b=3.501 A°,c=6.731 A°,β=111.76°.The solid-state phase transition fromα-MgV_(2)O_(6)toβ-MgV_(2)O_(6)was further studied by thermal kinetics,indicating that this process is controlled first by a fibril-like mechanism and then by a spherulitic-type mechanism with an increasing heating rate.Additionally,the enthalpy change of MgV_(2)O_(6)at high temperatures was measured utilizing the drop calorimetry,heat capacity was calculated and given as:Cp=208.3+0.03583T-4809000T^(−2)(298-923 K)(J mol^(−1)K^(−1)),the high-temperature heat capacity can be used to calculate Gibbs free energy of MgV_(2)O_(6)at high temperatures.
基金supported by the NSAF under Grant No.U1930201the National Natural Science Foundation of China(NSFC)under Grant Nos.12274331,91836101,12135018,12204428the Innovation Program for Quantum Science and Technology under Grant No.2021ZD0302100。
文摘Multiple quantum coherences are often employed to describe quantum many-body dynamics in nuclear spin systems and recently,to characterize quantum phase transitions in trapped ions.Here we investigate the multiple-quantum-coherence dynamics of a spin-1 Bose–Einstein condensate.By adjusting the quadratic Zeeman shift,the condensate exhibits three quantum phases.Our numerical results show that the spectrum of multiple quantum coherence does indeed catch the quantum critical points.More importantly,with only a few low-order multiple quantum coherences,the spin-1 condensate exhibits rich signals of the many-body dynamics,beyond conventional observables.The experimental implementation of such multiple quantum coherence protocol is also discussed.
基金National Natural Science Foundation of China,No.42301313Natural Science Foundation of Guangxi Zhuang Autonomous Region,No.2024GXNSFBA010097National Natural Science Foundation of China,No.41971216。
文摘The ecological function of land use is the basis for developing an ecological civilization and realizing sustainable development.This paper may help guide the coordination of economic development and ecological development in China’s coastal border areas.Based on theoretical analysis,this paper studies the spatiotemporal evolution of the functional spaces and the ecological function transitions of land use in the Beibu Gulf Economic Zone(BGEZ)by analyzing patterns,processes,and factors by applying eco-environmental quality index,grid subdivision,kriging interpolation,barycenter model,and Geodetector.This paper constructs a theoretical framework of ecological function transitions of land use based on the research idea of“system-pattern-process-factor”,and carries out empirical research.Some conclusions can be drawn as follows:(1)The ecological space in the BGEZ has continuously decreased,converting mainly into agricultural production space and industrial-mining production space.The production space has expanded slowly.The area of living space in the BGEZ has increased rapidly.(2)The ecological function of land use in the BGEZ has continued to weaken,especially in the southern part of the BGEZ.The“high-sub-high”quality zones of ecological function are retreating to the north.(3)There were more deterioration transition areas than optimization transition areas of ecological function in the BGEZ.The former were mostly located in the central and southern urbanized areas of the BGEZ,whereas the latter were mostly located in the edge zones of district and county units.(4)As for the driving factors of the deterioration transitions of land use ecological function in the BGEZ,the significant trend of“de-ecologization”of the land cover/land use structure was the dominant driving factor;the interactions among the“natural-socioeconomic-managerial”systems were the main recessive factor.The natural system played a fundamental role,and the driving force of natural factors was the strongest.The industrialization,urbanization,and GDP increment in the socioeconomic system and the policy positioning of development intensity in the managerial system played a significant role.The interactions among natural factors,road construction,and industrial non-agricultural transformation had a“fuze”effect on stimulating driving forces.
