Free oscillations of magnetic fluid in strong magnetic field

The paper presents the esults of measuring the elastic parameters of an oscillatory system (coefficient of pondermotive elasticity, damping factor, and oscillation frequency) whose viscous inertial element is represented by a magnetic fluid confined in a tube by magnetic levitation in a strong magnetic field. The role of elasticity is played by the pondermotive force acting on thin layers at the upper and lower ends of the fluid column. It is shown that, by measuring the elastic oscillation frequencies of the magnetic fluid column, it is possible to develop a fundamentally new absolute method for determining the saturation magnetization of a magnetic colloid.     

Two-dimensional quantum antiferromagnet in a strong magnetic field

The behaviour of the two-dimensional quantum antiferromagnet of arbitrary spin in a strong transversal magnetic field on a square lattice is studied in terms of the equivalent Bose gas problem. The existence of phase transition from the state characterized by “quasi-long-range” magnetic order to the disordered ferromagnetic state is demonstrated. The expressions for correlation functions, thermodynamical and magnetic characteristics are derived.     

D − center in quantum well with strong magnetic field

We consider a system composed of two electrons moving in an infinite quantum well with an ionized donor in the presence of a strong magnetic field. The binding energies of the ground state and some low-lying excited states are calculated with a variational method. The effects of the well-width on the binding energies of this system are investigated. Our results are suitable for both two-dimensional and three-dimensional conditions. When the well-width goes to infinite, the results go to the results for three-dimensional case. And when the wellwidth goes to zero, the results are in agreement with that for two-dimensional condition.     

Prediction of strong magnetic quantum oscillations of the nuclear spin relaxation in a quasi-two-dimensional metal

The nuclear spin lattice relaxation rate in a quasi-two-dimensional (2-D) metal under strong magnetic fields is studied in a special case where the electronic cyclotron mass is small compared with the free electron mass. In the pure limit (ω_cτ ? 1) and for sufficiently low temperatures ($\text{h}\text{?}\text{ω}{}_{\mathrm{c}}\text{> 2π}{}^2\text{k}{}_{\mathrm{B}}\text{T}$) we find remarkable quantum oscillations of the relaxation rate as a function of the magnetic field. The period of these oscillations is identical to that of the de Haas-van Alphen oscillations and their amplitude grows linearly with the magnetic field. The possibility of observing such oscillations experimentally in the quasi-2-D mercury chain compound Hg_3?δAsF₆ is discussed.     

耦合电磁场对石墨烯量子磁振荡的影响

我们研究了包含自旋轨道耦合与杂质散射在内的石墨烯量子磁振荡对外加电磁场的响应.我们发现,石墨烯中自旋轨道耦合、电磁场以及边界共同修正了朗道能谱,且当电场与磁场比值超过某一临界值时,量子磁振荡会突然消失,这与非相对论二维电子气的情况显著不同.这种现象可以通过朗道量子化轨道由封闭转化为开放的半经典理论来解释.此外,我们还发现杂质散射和温度的共同作用会使得磁振荡振幅衰减.我们的结果可用于分析石墨烯及其类似结构(硅烯、锗烯、锡烯等)的费米能级与朗道能谱的相互作用,进而探测自旋轨道耦合引起的能隙.     

Excitation hierarchy of the quantum sine-gordon spin chain in a strong magnetic field

The magnetic excitation spectrum of copper pyrimidine dinitrate, a material containing S = 1 / 2 antiferromagnetic chains with alternating g tensor and the Dzyaloshinskii-Moriya interaction and exhibiting a field-induced spin gap, is probed using submillimeter wave electron spin resonance spectroscopy. Ten excitation modes are resolved in the low-temperature spectrum, and their frequency-field diagram is systematically studied in magnetic fields up to 25 T. The experimental data are sufficiently detailed to make a very accurate comparison with predictions based on the quantum sine-Gordon field theory. Signatures of three breather branches and a soliton, as well as those of several multiparticle excitation modes, are identified.     

Commensurability oscillations in a quasi-two-dimensional electron gas subject to strong in-plane magnetic field

We report on a theoretical study of the commensurability oscillations in a quasi-two-dimensional electron gas modulated by a unidirectional periodic potential and subject to tilted magnetic fields with a strong in-plane component. As a result of coupling of the in-plane field component and the confining potential in the finite-width quantum well, the originally circular cyclotron orbits become anisotropic and tilted out of the sample plane. A quasi-classical approach to the theory, that relates the magneto-resistance oscillations to the guiding-center drift, is extended to this case.     

Magnetic quantum oscillations in a monolayer graphene under a perpendicular magnetic field

The de Haas-van Alphen(dHvA) oscillations of electronic magnetization in a monolayer graphene with structureinduced spin-orbit interaction(SOI) are studied.The results show that the dHvA oscillating centre in this system deviates from the well known(zero) value in a conventional two-dimensional electron gas.The inclusion of SOI will change the well-defined sawtooth pattern of magnetic quantum oscillations and result in a beating pattern.In addition,the SOI effects on Hall conductance and magnetic susceptibility are also discussed.     

Coulomb oscillations of conductance in an open ring interferometer in a strong magnetic field

Under the conditions corresponding to tunnel-coupled edge current states in an open ring interferometer, oscillations of conductance as a function of gate voltage with two noticeably different periods are observed. The large-period oscillations are attributed to the electron tunneling between the source and drain regions via a closed edge state of the ring, when an integral number of magnetic flux quanta passes through its contour at the Fermi level. The small-period oscillations are explained by the effect of single-electron variations of the ring potential on the transparency of the barriers between the localized and delocalized edge states of the interfer-ometer.     

Magnetic susceptibility of a two-dimensional electron gas in the quantum strong magnetic field limit

It is shown that the peak values of the magnetic susceptibility of a two-dimensional electron gas in the quantum strong magnetic field limit are integral multiples of $\text{μ}{}^2{}_{\mathrm{B}}\text{2π}$.     

Giant Nernst-Ettingshausen oscillations in semiclassically strong magnetic fields

We consider the Nernst-Ettingshausen (NE) effect in the presence of semiclassically strong magnetic fields for a quasi-two-dimensional system with a parabolic or linear dispersion of carriers. We show that the occurring giant oscillations of the NE coefficient are coherent with the recent experimental observation in graphene, graphite, and bismuth. In the 2D case we find the exact shape of these oscillations and show that their magnitude decreases (increases) with enhancement of the Fermi energy for Dirac fermions (normal carriers). With a crossover to the 3D spectrum the phase of the oscillations shifts, their amplitude decreases, and the peaks become asymmetric.     

Light propagation in a strong external magnetic field with regard to quantum corrections

Linearized motion equations for electromagnetic wave field in the external magnetic field have been solved for the PVLAS experiment configuration within the low-energy approximation of quantum electrodynamics. It has been shown that the wave propagation velocity depends on the initial direction of the plane of wave polarization. Dispersion laws corresponding to the waves with mutually perpendicular directions of polarization have been established. The dependence of ellipticity of laser radiation field on initial polarization and the value of the external magnetic field has been obtained. The ellipticity parameter for the configuration of the system used in the PVLAS experiment has been found.     

Multiphonon decay of strong mode in quantum lattice

A nonperturbative theory of multiphonon anharmonic decay of strongly excited local mode is developed whereby the mode is considered classically and phonons, quantum mechanically. The decay rate of the mode is expressed via the negative frequency parts of the phonon pair correlation functions. In the case of two-phonon decay the later satisfy the linear integral equations while in the case of two- and more-phonon decay they satisfy the nonlinear integral equations. As a result, the processes mentioned differently depend on the mode amplitude A: two-phonon processes smoothly deminish if A → ∞ while three- and more-phonon processes are fully switched-off at large amplitudes and they abruptly switch-on if the amplitude approaches the critical value. At that the decay rate gets rather high value (of the order of the mode quantum per period). The final stage of the relaxation is well described by the perturbation theory.     

Radial oscillations of neutron stars in strong magnetic fields

The eigen frequencies of radial pulsations of neutron stars are calculated in a strong magnetic field. At low densities we use the magnetic BPS equation of state (EOS) similar to that obtained by Lai and Shapiro while at high densities the EOS obtained from the relativistic nuclear mean field theory is taken and extended to include strong magnetic field. It is found that magnetized neutron stars support higher maximum mass whereas the effect of magnetic field on radial stability for observed neutron star masses is minimal.     

Covariant Wigner function approach to the relativistic quantum electron gas in a strong magnetic field

This paper is concerned with a unified approach to some equilibrium properties of the relativistic quantum electron plasma embedded in a strong external magnetic field. This unified approach rests on the systematic use of a covariant Wigner function. The equilibrium Wigner function of the noninteracting gas is derived and its main properties are studied. In particular, it satisfies equations that are the complete analog of the usual Liouville equation and thus can be termed “relativistic quantum Liouville equation” whose properties are considered. The equations of state are rederived in this formalism and the results obtained earlier by Canuto and Chiu are found anew. Also, the covariant Wigner funetion of the magnetized vacuum is derived: it is needed, in this formalism, in order to obtain, e.g., the vacuum polarization tensor. Since we are also interested in the plasma modes, the fluctuations of one-particle quantities—and their spectrum—(in particular, of the four current) are calculated in view of their use in the fluctuation-dissipation theorem. We also outline a microscopic proof of this theorem, on the basis of a BBGKY hierarchy for the covariant Wigner functions, and point out the existence of an effective plasma frequency.     

Impurity states of narrow-gap semiconductor parabolic quantum dot in the presence of extremely strong magnetic field

The impurity states in a narrow-gap semiconductor parabolic quantum dot in the presence of external extremely strong magnetic field are considered in adiabatic approximation framework. Moreover, the dispersion law for impurity electron is described by using the Kane's two-band approximation. The effective one-dimensional equation describing the impurity electron's state along the field is obtained. The analytical expressions for total and binding energies of impurity ground state are obtained. The dependences of total and binding energies of impurity on the value of magnetic field and on the size of quantum dot are investigated.     

磁场中的拓扑绝缘体边缘态性质

用数值方法研究了拓扑绝缘体薄膜体系在外加垂直磁场 作用下其边缘态的性质. 磁场的加入通过耦合k+eA, 即Peierls势替换关系和 该作用导致的Zeeman交换场体现在哈密顿量中. 考虑窄条圆环状结构的二维InAs/GaSb/AlSb薄膜量子阱材料, 当其处于拓扑非平庸状态, 即量子自旋霍尔态时, 会出现受时间反演对称性保护的两支简并边缘态, 而在垂直磁场的作用下, 时间反演对称性被破坏, 这时能带将形成一条条的朗道能级, 原来简并的两支边缘态也会分开到朗道能级谱线的两侧, 从电子态密度的空间分布情况则可以看到边缘态分别局域在材料的两个边界. 随着磁场的增大, 位于同一边界上的不同 自旋极化的边缘态将出现分离: 一支仍然局域在边缘, 另一支则随外加磁场的增加而有逐渐演化到材料内部的趋势. 文中还计算了同一边界上的两支边缘态之间的散射, 结果表明由于两个边缘态在空间发生分离, 相互之间的散射被很大的压制, 得到了其散射随磁场增加没有明显变化的结论, 所以磁场并不会增强散射过程, 也没有破坏体拓扑材料的性质, 说明了量子自旋霍尔态在没有时间反演对称的情况下也可以有较强的稳定性.