Unconventional Landau Levels of Ultracold Fermionic Atoms on Two-Dimensional Honeycomb Lattice

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.

Observation of an Even-Odd Asymmetric Transport in High Landau Levels

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.

Landau-like quantized levels of neutral atom induced by a dark-soliton shaped electric field

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.

Charged Particle in a Flat Box with Static Electromagnetic Field and Landau’s Levels

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.

Behavior of fractional quantum Hall states in LLL and 1LL with in-plane magnetic field and Landau level mixing:A numerical investigation

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.

Landau level transitions in InAs/AlSb/GaSb quantum wells

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.

Disorder-enhanced nuclear spin relaxation at Landau level filling factor one

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.

Ehrenfest Approach to the Adiabatic Invariants and Calculation of the Intervals of Time Entering the Energy Emission Process in Simple Quantum Systems

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.

A possible mechanism for magnetar soft X-ray/γ-ray emission

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.

Theoretical Models of Highly Magnetic White Dwarf Stars with Non-Polytropic Equation of State

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.

The Density of Energy States for Nonparabolic Dispersion Law in a Strong Magnetic Field

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.

Landau quantization and spin polarization of cold magnetized quark matter

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.

声学三维量子霍尔态的观测

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.

非厄米趋肤效应的赝磁抑制

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.

Chiral magnetic effect for chiral fermion system

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.

Backward Compton scattering and QED with noncommutative plane in the strong uniform magnetic field

In the strong uniform magnetic field, the noncommutative plane （NCP） caused by the lowest Landau level （LLL） effect, and QED with NCP （QED-NCP） are studied. Being similar to the condensed matter theory of quantum Hall effect, an effective filling factor f（B） is introduced to characterize the possibility that the electrons stay on the LLL. The analytic and numerical results of the differential cross section for the process of backward Compton scattering in accelerator with unpolarized or polarized initial photons are calculated. The existing data of BL38B2 in Spring-8 have been analyzed roughly and compared with the numerical predictions primitively. We propose a precise measurement of the differential cross sections of backward Compton scattering in a strong perpendicular magnetic field, which may reveal the effects of NCP.

Evolution of individual quantum Hall edge states in the presence of disorder

By using the Bloch eigenmode matching approach, we numerically study the evolution of individual quantum Hall edge states with respect to disorder. As demonstrated by the two-parameter renormal- ization group flow of the Hall and Thouless conductances, quantum Hall edge states with high Chern number n are completely different from that of the n = 1 case. Two categories of individual edge modes are evaluated in a quantum Hall system with high Chern number. Edge states from the lowest Landau level have similar eigenfunctions that are well localized at the system edge and independent of the Fermi energy. On the other hand, at fixed Fermi energy, the edge state from higher Landau levels exhibit larger expansion, which results in less stable quantum Hall states at high Fermi energies. By presenting the local current density distribution, the effect of disorder on eigenmode-resolved edge states is distinctly demonstrated.