We investigate the unconventional Landau levels of ultracold fermionic atoms on the two-dimensionalhoneycomb optical lattice subjected to an effective magnetic field,which is created with optical means.In the presence...We investigate the unconventional Landau levels of ultracold fermionic atoms on the two-dimensionalhoneycomb optical lattice subjected to an effective magnetic field,which is created with optical means.In the presenceof the effective magnetic field,the energy spectrum of the unconventional Landau levels is calculated.Furthermore,wepropose to detect the unconventional Landau levels with Bragg scattering techniques.展开更多
Magnetotransport experiments including tilt fields are performed on ultrahigh mobility L-shaped Hall-bar samples of GaAs/AlGaAs quantum wells. The low-temperature longitudinal resistivity （ρxx） data demonstrate tha...Magnetotransport experiments including tilt fields are performed on ultrahigh mobility L-shaped Hall-bar samples of GaAs/AlGaAs quantum wells. The low-temperature longitudinal resistivity （ρxx） data demonstrate that a striking even-odd asymmetric transport exists along the [110] direction at half filling in N ≥ 2 high Landau levels. Although the origin for the peculiar even-odd asymmetry remains unclear, we propose that the coupling strength between electrons within the same Landau level and between the neighboring two Landau levels should be considered in future studies. The tilt field data show that the in-plane field can suppress the formation of both bubble and stripe phases.展开更多
Landau levels,previously proposed and verified in condensed matter systems,are conventionally achieved by introducing an external magnetic field that interacts with electrons.In phononic systems,people have proposed t...Landau levels,previously proposed and verified in condensed matter systems,are conventionally achieved by introducing an external magnetic field that interacts with electrons.In phononic systems,people have proposed the method of applying strain to structures to form artificial synthetic magnetic fields,which in turn induces the emergence of Landau levels.While most of the current implementations about Landau levels are based on three-dimensional(3D)Weyl systems,the experimental realization of chiral Landau levels in two-dimensional(2D)Dirac acoustic systems remains an open and interesting topic.In this work,we present an innovative approach to generate the chiral Landau levels within a 2D acoustic system by introducing an in-plane artificial pseudomagnetic field.Through breaking the spatial parity symmetry and opening the Dirac cones,we introduce position-dependent effective mass terms to Hamiltonian and confirm the existence of chiral Landau levels by simulations and experiments.Furthermore,We verify the strong robustness of the zeroth Landau level to different kinds of defects.This work provides a feasible way to realize chiral Landau levels in 2D acoustic systems and suggests potential applications in other 2D artificial structures.展开更多
Motivated by the fascinating progresses in the cold atom experiments and theories,especially the artificial gauge field induced spin–orbit coupling of neutral atoms,we present a novel dispersion of neutral atoms carr...Motivated by the fascinating progresses in the cold atom experiments and theories,especially the artificial gauge field induced spin–orbit coupling of neutral atoms,we present a novel dispersion of neutral atoms carrying a non-vanishing magnetic moment in a special gauge field,an external electric field of dark-soliton shaped profile.By means of WKB approximation,we obtain discrete quantized landau-like energy levels,which is instructive for the quantum Hall effect of neutral particles.The observability of the results is also discussed.展开更多
We study the quantization of a charged particle motion without spin inside a flat box under a static electromagnetic field. Contrary to Landau’s solution with constant magnetic field transverse to the box and using F...We study the quantization of a charged particle motion without spin inside a flat box under a static electromagnetic field. Contrary to Landau’s solution with constant magnetic field transverse to the box and using Fourier transformation, we found a full solution for the wave function which is different from that one given by Landau, and this fact remains when static electric field is added. However, the Landau’s levels appear in all cases.展开更多
The spectrum of cold fermionic atoms is studied in a trilayer honeycomb optical lattice subjected to a perpendicular effective magnetic field,which is created with optical means.In the low energy approximation,the spe...The spectrum of cold fermionic atoms is studied in a trilayer honeycomb optical lattice subjected to a perpendicular effective magnetic field,which is created with optical means.In the low energy approximation,the spectrum shows unconventional Landau levels,which are proportional to the 3/2 power of integer numbers.The zoro modes exist and the quasiparticles are chiral.It is also proposed to identify the unconventional Landau levels via probing the dynamic structure factor of the system with Bragg spectroscopy.展开更多
By exactly solving the effective two-body interaction for a two-dimensional electron system with layer thickness and an in-plane magnetic field, we recently found that the effective interaction can be described by the...By exactly solving the effective two-body interaction for a two-dimensional electron system with layer thickness and an in-plane magnetic field, we recently found that the effective interaction can be described by the generalized pseudopoten- tials （PPs） without the rotational symmetry. With this pseudopotential description, we numerically investigate the behavior of the fractional quantum Hall （FQH） states both in the lowest Landau level （LLL） and first excited Landau level （1LL）. The enhancements of the 7/3 FQH state on the 1LL for a small tilted magnetic field are observed when layer thickness is larger than some critical values, while the gap of the 1/3 state in the LLL monotonically reduced with increasing the in-plane field. From the static structure factor calculation, we find that the systems are strongly anisotropic and finally enter into a stripe phase with a large tilting. With considering the Landau level mixing correction on the two-body interaction, we find the strong LL mixing cancels the enhancements of the FQH states in the 1LL.展开更多
The electronic structure of InAs/AlSb/GaSb quantum wells embedded in AlSb barriers and in the presence of a perpendicular magnetic field is studied theoretically within the 14-band ？？ · ？？ approach without ma...The electronic structure of InAs/AlSb/GaSb quantum wells embedded in AlSb barriers and in the presence of a perpendicular magnetic field is studied theoretically within the 14-band ？？ · ？？ approach without making the axial approximation.At zero magnetic field, for a quantum well with a wide In As layer and a wide GaSb layer, the energy of an electron-like subband can be lower than the energy of hole-like subbands. As the strength of the magnetic field increases, the Landau levels of this electron-like subband grow in energy and intersect the Landau levels of the hole-like subbands. The electron–hole hybridization leads to a series of anti-crossing splittings of the Landau levels. The magnetic field dependence of some dominant transitions is shown with their corresponding initial-states and final-states indicated. The dominant transitions at high fields can be roughly viewed as two spin-split Landau level transitions with many electron–hole hybridization-induced splittings. When the magnetic field is tilted, the electron-like Landau level transitions show additional anti-crossing splittings due to the subband-Landau level coupling.展开更多
The nuclear spin relaxation rate （l/T1） is measured for GaAs two-dimensional （2D） electron systems in the quantum Hall regime with an all-electrical technique for agitating and probing the nuclear spins. A ＂tilte...The nuclear spin relaxation rate （l/T1） is measured for GaAs two-dimensional （2D） electron systems in the quantum Hall regime with an all-electrical technique for agitating and probing the nuclear spins. A ＂tilted plateau＂ feature is observed near the Landau level filling factor v = 1 in 1/T1 versus v. Both the width and magnitude of the plateau increase with decreasing electron density. At low temperatures, lIT1 exhibits an Arrhenius temperature dependence within the tilted plateau regime. The extracted energy gaps are up to two orders of magnitude smaller than the corresponding charge transport gaps. These results point to a nontrivial mechanism for the disorder-enhanced nuclear spin relaxation, in which microscopic inhomogeneities play a key role for the low energy spin excitations related to skyrmions.展开更多
In the first step, the Ehrenfest reasoning concerning the adiabatic invariance of the angular orbital momentum is applied to the electron motion in the hydrogen atom. It is demonstrated that the time of the energy emi...In the first step, the Ehrenfest reasoning concerning the adiabatic invariance of the angular orbital momentum is applied to the electron motion in the hydrogen atom. It is demonstrated that the time of the energy emission from the quantum level n+1 to level n can be deduced from the orbital angular momentum examined in the hydrogen atom. This time is found precisely equal to the time interval dictated by the Joule-Lenz law governing the electron transition between the levels n+1 and n. In the next step, the mechanical parameters entering the quantum systems are applied in calculating the time intervals characteristic for the electron transitions. This concerns the neighbouring energy levels in the hydrogen atom as well as the Landau levels in the electron gas submitted to the action of a constant magnetic field.展开更多
Once the energies of electrons near the Fermi surface obviously exceed the threshold energy of the inverse β decay,electron capture（EC） dominates inside the magnetar.Since the maximal binding energy of the 3 P 2 ne...Once the energies of electrons near the Fermi surface obviously exceed the threshold energy of the inverse β decay,electron capture（EC） dominates inside the magnetar.Since the maximal binding energy of the 3 P 2 neutron Cooper pair is only about 0.048 MeV,the outgoing high-energy neutrons（E k（n） 60 MeV） created by the EC can easily destroy the 3 P 2 neutron Cooper pairs through the interaction of nuclear force.In the anisotropic neutron superfluid,each 3 P 2 neutron Cooper pair has magnetic energy 2μ n B in the applied magnetic field B,where μ n = 0.966 × 10 23 erg.G 1 is the absolute value of the neutron abnormal magnetic moment.While being destroyed by the high-energy EC neutrons,the magnetic moments of the 3 P 2 Cooper pairs are no longer arranged in the paramagnetic direction,and the magnetic energy is released.This released energy can be transformed into thermal energy.Only a small fraction of the generated thermal energy is transported from the interior to the surface by conduction,and then it is radiated in the form of thermal photons from the surface.After highly efficient modulation within the star＇s magnetosphere,the thermal surface emission is shaped into a spectrum of soft X-rays/γ-rays with the observed characteristics of magnetars.By introducing related parameters,we calculate the theoretical luminosities of magnetars.The calculation results agree well with the observed parameters of magnetars.展开更多
Super-massive white dwarf (WD) stars in the mass range 2.4 - 2.8 solar masses are believed to be the progenitors of “super-luminous” Type Ia supernovae according to a hypothesis proposed by some researchers. They th...Super-massive white dwarf (WD) stars in the mass range 2.4 - 2.8 solar masses are believed to be the progenitors of “super-luminous” Type Ia supernovae according to a hypothesis proposed by some researchers. They theorize such a higher mass of the WD due to the presence of a very strong magnetic field inside it. We revisit their first work on magnetic WDs (MWDs) and present our theoretical results that are very different from theirs. The main reason for this difference is in the use of the equation of state (EoS) to make stellar models of MWDs. An electron gas in a magnetic field is Landau quantized and hence, the resulting EoS becomes non-polytropic. By constructing models of MWDs using such an EoS, we highlight that a strong magnetic field inside a WD would make the star super-massive. We have found that our stellar models do indeed fall in the mass range given above. Moreover, we are also able to address an observational finding that the mean mass of MWDs are almost double that of non-magnetic WDs. Magnetic field changes the momentum-space of the electrons which in turn changes their density of states (DOS), and that in turn changes the EoS of matter inside the star. By correlating the magnetic DOS with the non-polytropic EoS, we were also able to find a physical reason behind our theoretical result of super-massive WDs with strong magnetic fields. In order to construct these models, we have considered different equations of state with at most three Landau levels occupied and have plotted our results as mass-radius relations for a particular chosen value of maximum Fermi energy. Our results also show that a multiple Landau-level system of electrons leads to such an EoS that gives multiple branches in the mass-radius relations, and that the super-massive MWDs are obtained when the Landau-level occupancy is limited to just one level. Finally, our theoretical results can be explained solely on the basis of quantum and statistical mechanics that warrant no assumptions regarding stars.展开更多
For nonparabolic dispersion law is determined by the density of the energy states (Ns) in a quantizing magnetic field. The effect of temperature on the expansion of the Lan-dau levels of electrons semiconductors with ...For nonparabolic dispersion law is determined by the density of the energy states (Ns) in a quantizing magnetic field. The effect of temperature on the expansion of the Lan-dau levels of electrons semiconductors with the nonquadratic dispersion is studied. The density of states at low temperatures is calculated from data on high-tem- perature Ns.展开更多
While conventional topological states can be used for robust acoustic energy transportation,the energy capacity is limited and the propagation route is also heavily constrained.In this work,we show that Landau levels ...While conventional topological states can be used for robust acoustic energy transportation,the energy capacity is limited and the propagation route is also heavily constrained.In this work,we show that Landau levels in acoustic systems can offer exciting new avenues for transporting acoustic energies.In particular,we realize valley-dependent Landau levels in a two-dimensional inhomogeneous acoustic system induced by synthetic in-plane magnetic fields.The band diagrams of the 0th-and 1st-order Landau levels are experimentally measured and their robustness of propagation against defects is also experimentally validated.Promising ways for acoustic energy transportation enabled by the Landau levels,such as large-area transportation and snake-like transportation are experimentally demonstrated.Importantly,we achieve topological propagation along an arbitrary prescribed path using unique features of the valley-dependent Landau levels for the first time in experiment,which is a significant advancement beyond what can be achieved using conventional acoustic topological states based on valley/spin Hall physics.These remarkable features open up promising opportunities for developing novel acoustic devices to realize robust,broadband,and flexible large-area acoustic energy conveying.展开更多
The magnetic field and density behaviors of various thermodynamic quantities of strange quark matter under compact star conditions are investigated in the framework of the thermodynamically self-consistent quasipartic...The magnetic field and density behaviors of various thermodynamic quantities of strange quark matter under compact star conditions are investigated in the framework of the thermodynamically self-consistent quasiparticle model.For individual species,a larger number density n_(i) leads to a larger magnetic field strength threshold that aligns all particles parallel or antiparallel to the magnetic field.Accordingly,in contrast to the finite baryon density effect which reduces the spin polarization of magnetized strange quark matter,the magnetic field effect leads to an enhancement of it.We also compute the sound velocity as a function of the baryon density and find the sound velocity shows an obvious oscillation with increasing density.Except for the oscillation,the sound velocity grows with increasing density,similar to the zero-magnetic field case,and approaches the conformal limit V_(s)^(2)=1/3 at high densities from below.展开更多
Magneto-transport study has been performed in topological semimetal ZrSiS single crystals under high pulsed magnetic fields.Obvious dependence of Landau level splitting on temperature and angular was investigated.The ...Magneto-transport study has been performed in topological semimetal ZrSiS single crystals under high pulsed magnetic fields.Obvious dependence of Landau level splitting on temperature and angular was investigated.The strong three-dimensional anisotropic nature of Landau level splitting under high pulsed magnetic fields was revealed by the angular dependent measurements,in which the orbital contribution is more dominant than Zeeman splitting.Our studies provide more insights into the physical properties of topological semimetals ZrSiS and shed light on future spintronic applications of ZrSiS.展开更多
Pseudomagnetic fields(PMFs)can manipulate photons in a similar way that magnetic fields control electrons.However,the PMF-based control over light has been restricted to simple waveguiding of the Landau level states,w...Pseudomagnetic fields(PMFs)can manipulate photons in a similar way that magnetic fields control electrons.However,the PMF-based control over light has been restricted to simple waveguiding of the Landau level states,which hinders the application of PMFs in practical photonic integrated circuits.Here,we propose a universal and systematic methodology to design complex nonuniform PMFs and arbitrarily control the flow of light in silicon photonic crystals at telecommunication wavelengths.As proofs of concept,an S-bend(with a low insertion loss of<1.83 dB)and a 50:50 power splitter(with a low excess loss of<2.11 dB and imbalance of less than±0.5 dB)based on PMFs are experimentally demonstrated.A high-speed data transmission experiment is performed on these devices with 140-Gb∕s four-level pulse amplitude modulation signals to prove their applicability in real communication systems.The proposed method offers a paradigm for exploring magnetic-field-related physics with neutral particles and developing nanophotonic devices with PMF-induced states beyond the Landau level states and the topological edge states.展开更多
Quantum Hall effect,the quantized transport phenomenon of electrons under strong magnetic fields,remains one of the hottest research topics in condensed matter physics since its discovery in 2D electronic systems.Rece...Quantum Hall effect,the quantized transport phenomenon of electrons under strong magnetic fields,remains one of the hottest research topics in condensed matter physics since its discovery in 2D electronic systems.Recently,as a great advance in the research of quantum Hall effects,the quantum Hall effect in 3D systems,despite its big challenge,has been achieved in the bulk ZrTe_(5)and Cd_(3)As_(2)materials.Interestingly,Cd_(3)As_(2)is a Weyl semimetal,and quantum Hall effect is hosted by the Fermi arc states on opposite surfaces via the Weyl nodes of the bulk,and induced by the unique edge states on the boundaries of the opposite surfaces.However,such intriguing edge state distribution has not yet been experimentally observed.Here,we aim to reveal experimentally the unusual edge states of Fermi arcs in acoustic Weyl system with the aid of pseudo-magnetic field.Benefiting from the macroscopic nature of acoustic crystals,the pseudo-magnetic field is introduced by elaborately designed the gradient onsite energy,and the edge states of Fermi arcs on the boundaries of the opposite surfaces are unambiguously demonstrated in experiments.Our system serves as an ideal and highly tunable platform to explore the Hall physics in 3D system,and has the potential in the application of new acoustic devices.展开更多
It has recently been shown that the non-Hermitian skin effect can be suppressed by magnetic fields. In this work, using a two-dimensional tight-binding lattice, we demonstrate that a pseudomagnetic field can also lead...It has recently been shown that the non-Hermitian skin effect can be suppressed by magnetic fields. In this work, using a two-dimensional tight-binding lattice, we demonstrate that a pseudomagnetic field can also lead to the suppression of the non-Hermitian skin effect. With an increasing pseudomagnetic field, the skin modes are found to be pushed into the bulk, accompanied by the reduction of skin topological area and the restoration of Landau level energies. Our results provide a time-reversal invariant route to localization control and could be useful in various classical wave devices that are able to host the non-Hermitian skin effect but inert to magnetic fields.展开更多
The chiral magnetic effect is concisely derived by employing the Wigner function approach in the chiral fermion system.Subsequently,the chiral magnetic effect is derived by solving the Landau levels of chiral fermions...The chiral magnetic effect is concisely derived by employing the Wigner function approach in the chiral fermion system.Subsequently,the chiral magnetic effect is derived by solving the Landau levels of chiral fermions in detail.The second quantization and ensemble average leads to the equation of the chiral magnetic effect for righthand and lefthand fermion systems.The chiral magnetic effect arises uniquely from the contribution of the lowest Landau level.We carefully analyze the lowest Landau level and find that all righthand(chirality is+1)fermions move along the direction of the magnetic field,whereas all lefthand(chirality is-1)fermions move in the opposite direction of the magnetic field.Hence,the chiral magnetic effect can be explained clearly using a microscopic approach.展开更多
基金Supported by the Teaching and Research Foundation for the Outstanding Young Faculty of Southeast University
文摘We investigate the unconventional Landau levels of ultracold fermionic atoms on the two-dimensionalhoneycomb optical lattice subjected to an effective magnetic field,which is created with optical means.In the presenceof the effective magnetic field,the energy spectrum of the unconventional Landau levels is calculated.Furthermore,wepropose to detect the unconventional Landau levels with Bragg scattering techniques.
基金Supported by the National Basic Research Program of China under Grant Nos 2014CB920904 and 2013CB921702the National Natural Science Foundation of China under Grant Nos 11174340,11174357,91221203 and 91421303+2 种基金the Strategic Priority Research Program B of the Chinese Academy of Sciences under Grant No XDB07010100the Gordon and Betty Moore Foundation through the EPiQS initiative under Grant No GBMF4420the National Science Foundation of MRSEC under Grant No DMR-1420541
文摘Magnetotransport experiments including tilt fields are performed on ultrahigh mobility L-shaped Hall-bar samples of GaAs/AlGaAs quantum wells. The low-temperature longitudinal resistivity （ρxx） data demonstrate that a striking even-odd asymmetric transport exists along the [110] direction at half filling in N ≥ 2 high Landau levels. Although the origin for the peculiar even-odd asymmetry remains unclear, we propose that the coupling strength between electrons within the same Landau level and between the neighboring two Landau levels should be considered in future studies. The tilt field data show that the in-plane field can suppress the formation of both bubble and stripe phases.
基金supported by the National Key R&D Program of China(2022YFA1404500 and 2022YFA1404400)NSFC(12225408,12074183,12104226,12227809,and 12474439)Jiangsu Provincial NSF(BK20240061 and BK20233001).
文摘Landau levels,previously proposed and verified in condensed matter systems,are conventionally achieved by introducing an external magnetic field that interacts with electrons.In phononic systems,people have proposed the method of applying strain to structures to form artificial synthetic magnetic fields,which in turn induces the emergence of Landau levels.While most of the current implementations about Landau levels are based on three-dimensional(3D)Weyl systems,the experimental realization of chiral Landau levels in two-dimensional(2D)Dirac acoustic systems remains an open and interesting topic.In this work,we present an innovative approach to generate the chiral Landau levels within a 2D acoustic system by introducing an in-plane artificial pseudomagnetic field.Through breaking the spatial parity symmetry and opening the Dirac cones,we introduce position-dependent effective mass terms to Hamiltonian and confirm the existence of chiral Landau levels by simulations and experiments.Furthermore,We verify the strong robustness of the zeroth Landau level to different kinds of defects.This work provides a feasible way to realize chiral Landau levels in 2D acoustic systems and suggests potential applications in other 2D artificial structures.
基金Project supported by China Scholarship Council,Shanxi Province Natural Science Foundation,China(Grant No.201601D011009)the Enterprise Project(Grant No.01110116100051)+1 种基金Shanxi 1331KSC and 111 Project(Grant No.D18001)the National Natural Science Foundation of China(Grant Nos.11404415 and 61873154)
文摘Motivated by the fascinating progresses in the cold atom experiments and theories,especially the artificial gauge field induced spin–orbit coupling of neutral atoms,we present a novel dispersion of neutral atoms carrying a non-vanishing magnetic moment in a special gauge field,an external electric field of dark-soliton shaped profile.By means of WKB approximation,we obtain discrete quantized landau-like energy levels,which is instructive for the quantum Hall effect of neutral particles.The observability of the results is also discussed.
文摘We study the quantization of a charged particle motion without spin inside a flat box under a static electromagnetic field. Contrary to Landau’s solution with constant magnetic field transverse to the box and using Fourier transformation, we found a full solution for the wave function which is different from that one given by Landau, and this fact remains when static electric field is added. However, the Landau’s levels appear in all cases.
基金supported by the Teaching and Research Foundation for the Outstanding Young Faculty of Southeast University
文摘The spectrum of cold fermionic atoms is studied in a trilayer honeycomb optical lattice subjected to a perpendicular effective magnetic field,which is created with optical means.In the low energy approximation,the spectrum shows unconventional Landau levels,which are proportional to the 3/2 power of integer numbers.The zoro modes exist and the quasiparticles are chiral.It is also proposed to identify the unconventional Landau levels via probing the dynamic structure factor of the system with Bragg spectroscopy.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.11674041 and 91630205)Chongqing Research Program for Basic Research and Frontier Technology(Grant No.cstc2017jcyj AX0084)
文摘By exactly solving the effective two-body interaction for a two-dimensional electron system with layer thickness and an in-plane magnetic field, we recently found that the effective interaction can be described by the generalized pseudopoten- tials （PPs） without the rotational symmetry. With this pseudopotential description, we numerically investigate the behavior of the fractional quantum Hall （FQH） states both in the lowest Landau level （LLL） and first excited Landau level （1LL）. The enhancements of the 7/3 FQH state on the 1LL for a small tilted magnetic field are observed when layer thickness is larger than some critical values, while the gap of the 1/3 state in the LLL monotonically reduced with increasing the in-plane field. From the static structure factor calculation, we find that the systems are strongly anisotropic and finally enter into a stripe phase with a large tilting. With considering the Landau level mixing correction on the two-body interaction, we find the strong LL mixing cancels the enhancements of the FQH states in the 1LL.
基金Project supported by the National Natural Science Foundation of China(Grant Nos.61076092 and 61290303)
文摘The electronic structure of InAs/AlSb/GaSb quantum wells embedded in AlSb barriers and in the presence of a perpendicular magnetic field is studied theoretically within the 14-band ？？ · ？？ approach without making the axial approximation.At zero magnetic field, for a quantum well with a wide In As layer and a wide GaSb layer, the energy of an electron-like subband can be lower than the energy of hole-like subbands. As the strength of the magnetic field increases, the Landau levels of this electron-like subband grow in energy and intersect the Landau levels of the hole-like subbands. The electron–hole hybridization leads to a series of anti-crossing splittings of the Landau levels. The magnetic field dependence of some dominant transitions is shown with their corresponding initial-states and final-states indicated. The dominant transitions at high fields can be roughly viewed as two spin-split Landau level transitions with many electron–hole hybridization-induced splittings. When the magnetic field is tilted, the electron-like Landau level transitions show additional anti-crossing splittings due to the subband-Landau level coupling.
基金Project supported by the National Basic Research Program of China(Grant Nos.2012CB921703 and 2015CB921102)the National Natural Science Foundation of China(Grant Nos.91121003,11374337,and 61425015)the Chinese Academy of Sciences,the BMBF,and the German–Israel Foundation
文摘The nuclear spin relaxation rate （l/T1） is measured for GaAs two-dimensional （2D） electron systems in the quantum Hall regime with an all-electrical technique for agitating and probing the nuclear spins. A ＂tilted plateau＂ feature is observed near the Landau level filling factor v = 1 in 1/T1 versus v. Both the width and magnitude of the plateau increase with decreasing electron density. At low temperatures, lIT1 exhibits an Arrhenius temperature dependence within the tilted plateau regime. The extracted energy gaps are up to two orders of magnitude smaller than the corresponding charge transport gaps. These results point to a nontrivial mechanism for the disorder-enhanced nuclear spin relaxation, in which microscopic inhomogeneities play a key role for the low energy spin excitations related to skyrmions.
文摘In the first step, the Ehrenfest reasoning concerning the adiabatic invariance of the angular orbital momentum is applied to the electron motion in the hydrogen atom. It is demonstrated that the time of the energy emission from the quantum level n+1 to level n can be deduced from the orbital angular momentum examined in the hydrogen atom. This time is found precisely equal to the time interval dictated by the Joule-Lenz law governing the electron transition between the levels n+1 and n. In the next step, the mechanical parameters entering the quantum systems are applied in calculating the time intervals characteristic for the electron transitions. This concerns the neighbouring energy levels in the hydrogen atom as well as the Landau levels in the electron gas submitted to the action of a constant magnetic field.
基金Project supported by the National Natural Science Foundation of China(Grant No.10773005)the National Basic Research Program of China(Grant No.2009CB824800)+1 种基金the Knowledge Innovation Program of the Chinese Academy of Sciences(Grant No.KJCX 2 -YW-T09)the Key Directional Project of the Chinese Academy of Sciences and the National Natural Science Foundation of China(Grant Nos.10173020,10673021,10778631 and 10903019)
文摘Once the energies of electrons near the Fermi surface obviously exceed the threshold energy of the inverse β decay,electron capture（EC） dominates inside the magnetar.Since the maximal binding energy of the 3 P 2 neutron Cooper pair is only about 0.048 MeV,the outgoing high-energy neutrons（E k（n） 60 MeV） created by the EC can easily destroy the 3 P 2 neutron Cooper pairs through the interaction of nuclear force.In the anisotropic neutron superfluid,each 3 P 2 neutron Cooper pair has magnetic energy 2μ n B in the applied magnetic field B,where μ n = 0.966 × 10 23 erg.G 1 is the absolute value of the neutron abnormal magnetic moment.While being destroyed by the high-energy EC neutrons,the magnetic moments of the 3 P 2 Cooper pairs are no longer arranged in the paramagnetic direction,and the magnetic energy is released.This released energy can be transformed into thermal energy.Only a small fraction of the generated thermal energy is transported from the interior to the surface by conduction,and then it is radiated in the form of thermal photons from the surface.After highly efficient modulation within the star＇s magnetosphere,the thermal surface emission is shaped into a spectrum of soft X-rays/γ-rays with the observed characteristics of magnetars.By introducing related parameters,we calculate the theoretical luminosities of magnetars.The calculation results agree well with the observed parameters of magnetars.
文摘Super-massive white dwarf (WD) stars in the mass range 2.4 - 2.8 solar masses are believed to be the progenitors of “super-luminous” Type Ia supernovae according to a hypothesis proposed by some researchers. They theorize such a higher mass of the WD due to the presence of a very strong magnetic field inside it. We revisit their first work on magnetic WDs (MWDs) and present our theoretical results that are very different from theirs. The main reason for this difference is in the use of the equation of state (EoS) to make stellar models of MWDs. An electron gas in a magnetic field is Landau quantized and hence, the resulting EoS becomes non-polytropic. By constructing models of MWDs using such an EoS, we highlight that a strong magnetic field inside a WD would make the star super-massive. We have found that our stellar models do indeed fall in the mass range given above. Moreover, we are also able to address an observational finding that the mean mass of MWDs are almost double that of non-magnetic WDs. Magnetic field changes the momentum-space of the electrons which in turn changes their density of states (DOS), and that in turn changes the EoS of matter inside the star. By correlating the magnetic DOS with the non-polytropic EoS, we were also able to find a physical reason behind our theoretical result of super-massive WDs with strong magnetic fields. In order to construct these models, we have considered different equations of state with at most three Landau levels occupied and have plotted our results as mass-radius relations for a particular chosen value of maximum Fermi energy. Our results also show that a multiple Landau-level system of electrons leads to such an EoS that gives multiple branches in the mass-radius relations, and that the super-massive MWDs are obtained when the Landau-level occupancy is limited to just one level. Finally, our theoretical results can be explained solely on the basis of quantum and statistical mechanics that warrant no assumptions regarding stars.
文摘For nonparabolic dispersion law is determined by the density of the energy states (Ns) in a quantizing magnetic field. The effect of temperature on the expansion of the Lan-dau levels of electrons semiconductors with the nonquadratic dispersion is studied. The density of states at low temperatures is calculated from data on high-tem- perature Ns.
基金supported by the University-Industry Collaborative Education Program of the Ministry of Education of China(Grant No.220804972162224)the National Natural Science Foundation of China(Grant Nos.92263208 and 12102134)+3 种基金the National Key R&D Program of China(Grant Nos.2022YFA1404400 and 2022YFA1404403)the Fundamental Research Funds for the Central Universities,the Research Grants Council of Hong Kong SAR(Grant Nos.15214323,15200922,15202820,and AoE/P-502/20)the Hong Kong Innovation and Technology Commission via project“Smart Railway Technology and Applications”(Grant No.K-BBY1)the Faculty Development Scheme(FDS)RGC Project(Grant No.UGC/FDS24/E04/21).
文摘While conventional topological states can be used for robust acoustic energy transportation,the energy capacity is limited and the propagation route is also heavily constrained.In this work,we show that Landau levels in acoustic systems can offer exciting new avenues for transporting acoustic energies.In particular,we realize valley-dependent Landau levels in a two-dimensional inhomogeneous acoustic system induced by synthetic in-plane magnetic fields.The band diagrams of the 0th-and 1st-order Landau levels are experimentally measured and their robustness of propagation against defects is also experimentally validated.Promising ways for acoustic energy transportation enabled by the Landau levels,such as large-area transportation and snake-like transportation are experimentally demonstrated.Importantly,we achieve topological propagation along an arbitrary prescribed path using unique features of the valley-dependent Landau levels for the first time in experiment,which is a significant advancement beyond what can be achieved using conventional acoustic topological states based on valley/spin Hall physics.These remarkable features open up promising opportunities for developing novel acoustic devices to realize robust,broadband,and flexible large-area acoustic energy conveying.
基金Support from the National Natural Science Foundation of China(11875181,11875052,11947098,12005005,61973109)the Hunan Provincial Natural Science Foundation of China(2021JJ40188)+4 种基金the Scientific Research Fund of Hunan Provincial Education Department of China(19C0772)the Scientific Research Fund of Hunan University of Science and Technology(E52059)the CAS pilot project(XDPB15)supported by the National Natural Science Foundation of China(11805087,11875153)the Fundamental Research Funds for the Central Universities(862946)。
文摘The magnetic field and density behaviors of various thermodynamic quantities of strange quark matter under compact star conditions are investigated in the framework of the thermodynamically self-consistent quasiparticle model.For individual species,a larger number density n_(i) leads to a larger magnetic field strength threshold that aligns all particles parallel or antiparallel to the magnetic field.Accordingly,in contrast to the finite baryon density effect which reduces the spin polarization of magnetized strange quark matter,the magnetic field effect leads to an enhancement of it.We also compute the sound velocity as a function of the baryon density and find the sound velocity shows an obvious oscillation with increasing density.Except for the oscillation,the sound velocity grows with increasing density,similar to the zero-magnetic field case,and approaches the conformal limit V_(s)^(2)=1/3 at high densities from below.
基金supported by the National Key Research and Development Program of China(Grant No.2016YFA0300803)the National Natural Science Foundation of China(Grant Nos.61427812,11774160,11574137,11874203,61822403,and U1732159)and the Fundamental Research Funds for the Central Universities(Grant No.021014380080),The authors also would like to thank the supports from the Collaborative Innovation Innovation Center of Solid State Lighting and Energy-saving Electronics and the Program for High-level Entrepreneurial and Innovative Talent Introduction,Jiangsu Province.
文摘Magneto-transport study has been performed in topological semimetal ZrSiS single crystals under high pulsed magnetic fields.Obvious dependence of Landau level splitting on temperature and angular was investigated.The strong three-dimensional anisotropic nature of Landau level splitting under high pulsed magnetic fields was revealed by the angular dependent measurements,in which the orbital contribution is more dominant than Zeeman splitting.Our studies provide more insights into the physical properties of topological semimetals ZrSiS and shed light on future spintronic applications of ZrSiS.
基金supported in part by the National Key Research and Development Program of China[Grant No.2023YFB2905503(L.S.)]the National Natural Science Foundation of China[Grant Nos.62035016(J.D.),62475146(L.S.),62105200(L.S.),and 62341508(Y.S.)].
文摘Pseudomagnetic fields(PMFs)can manipulate photons in a similar way that magnetic fields control electrons.However,the PMF-based control over light has been restricted to simple waveguiding of the Landau level states,which hinders the application of PMFs in practical photonic integrated circuits.Here,we propose a universal and systematic methodology to design complex nonuniform PMFs and arbitrarily control the flow of light in silicon photonic crystals at telecommunication wavelengths.As proofs of concept,an S-bend(with a low insertion loss of<1.83 dB)and a 50:50 power splitter(with a low excess loss of<2.11 dB and imbalance of less than±0.5 dB)based on PMFs are experimentally demonstrated.A high-speed data transmission experiment is performed on these devices with 140-Gb∕s four-level pulse amplitude modulation signals to prove their applicability in real communication systems.The proposed method offers a paradigm for exploring magnetic-field-related physics with neutral particles and developing nanophotonic devices with PMF-induced states beyond the Landau level states and the topological edge states.
基金supported by the National Key R&D Program of China(2022YFA1404500,2022YFA1404900)the National Natural Science Foundation of China(11890701,11974120,11974005,12034012,12074128,12074232,12125406,12204290,and 12374360)+2 种基金the National Postdoctoral Program(BX20220195 and 2023M732146)Shanxi"1331 Project"Cross-disciplinary Innovative Research Group Project of Henan Province(232300421004)。
文摘Quantum Hall effect,the quantized transport phenomenon of electrons under strong magnetic fields,remains one of the hottest research topics in condensed matter physics since its discovery in 2D electronic systems.Recently,as a great advance in the research of quantum Hall effects,the quantum Hall effect in 3D systems,despite its big challenge,has been achieved in the bulk ZrTe_(5)and Cd_(3)As_(2)materials.Interestingly,Cd_(3)As_(2)is a Weyl semimetal,and quantum Hall effect is hosted by the Fermi arc states on opposite surfaces via the Weyl nodes of the bulk,and induced by the unique edge states on the boundaries of the opposite surfaces.However,such intriguing edge state distribution has not yet been experimentally observed.Here,we aim to reveal experimentally the unusual edge states of Fermi arcs in acoustic Weyl system with the aid of pseudo-magnetic field.Benefiting from the macroscopic nature of acoustic crystals,the pseudo-magnetic field is introduced by elaborately designed the gradient onsite energy,and the edge states of Fermi arcs on the boundaries of the opposite surfaces are unambiguously demonstrated in experiments.Our system serves as an ideal and highly tunable platform to explore the Hall physics in 3D system,and has the potential in the application of new acoustic devices.
基金supported by National Research Foundation Singapore Competitive Research Program (NRF-CRP232019-0007)support from the start-up fund and the direct grant (4053675) of The Chinese University of Hong Kong。
文摘It has recently been shown that the non-Hermitian skin effect can be suppressed by magnetic fields. In this work, using a two-dimensional tight-binding lattice, we demonstrate that a pseudomagnetic field can also lead to the suppression of the non-Hermitian skin effect. With an increasing pseudomagnetic field, the skin modes are found to be pushed into the bulk, accompanied by the reduction of skin topological area and the restoration of Landau level energies. Our results provide a time-reversal invariant route to localization control and could be useful in various classical wave devices that are able to host the non-Hermitian skin effect but inert to magnetic fields.
基金Supported by the National Natural Science Foundation of China(11847220)in part Supported by the National Natural Science Foundation of China(11735007,11890711)。
文摘The chiral magnetic effect is concisely derived by employing the Wigner function approach in the chiral fermion system.Subsequently,the chiral magnetic effect is derived by solving the Landau levels of chiral fermions in detail.The second quantization and ensemble average leads to the equation of the chiral magnetic effect for righthand and lefthand fermion systems.The chiral magnetic effect arises uniquely from the contribution of the lowest Landau level.We carefully analyze the lowest Landau level and find that all righthand(chirality is+1)fermions move along the direction of the magnetic field,whereas all lefthand(chirality is-1)fermions move in the opposite direction of the magnetic field.Hence,the chiral magnetic effect can be explained clearly using a microscopic approach.
