Magnetic moment of an electron gas on the surface of constant negative curvature

The magnetic moment of an electron gas on the surface of constant negative curvature is investigated. It is shown that the surface curvature leads to the appearance of the region of the monotonic dependence M(B) at low magnetic fields. At high magnetic fields, the dependence of the magnetic moment on a magnetic field is the oscillating one. The effect of the surface curvature is to increase the region of the monotonic dependence of the magnetic moment and to break the periodicity of oscillations of the magnetic moment as a function of an inverse magnetic field.Received: 17 September 2003, Published online: 8 December 2003PACS: 73.20.At Surface states, band structure, electron density of states - 75.75. + a Magnetic properties of nanostructures     

Landau diamagnetism and determination of the longitudinal and transverse kinetic energy components of a degenerate nonrelativistic electron gas

The Fermi energy, average total kinetic energy density, and also average kinetic energy of finite diamagnetic motion of an electron gas of specified concentration are calculated. The kinetic energy of continuous longitudinal motion of the electrons along the direction of an external magnetic field H is determined. It is found that in the quantum limit, when the maximum Landau quantum number N _m =0, the kinetic energy of continuous longitudinal motion tends to zero with increase in the external magnetic field strength. If the maximum Landau quantum number is greater than zero, the longitudinal and transverse kinetic energy components of the degenerate electron gas change only insignificantly. Byelorussian State University; Brest State University. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 7, pp. 31–35, July, 1999.     

Quantum spin-glass transition in the two-dimensional electron gas

We discuss the possibility of spin-glass order in the vicinity of the unexpected metallic state of the two-dimensional electron gas in zero applied magnetic field. An average ferromagnetic moment may also be present, and the spin-glass order then resides in the plane orthogonal to the ferromagnetic moment. We argue that a quantum transition involving the destruction of the spinglass order in an applied in-plane magnetic field offers a natural explanation of some features of recent magnetoconductance measurements. We present a quantum field theory for such a transition and compute its mean field properties.     

中子星中简并电子气体的临界磁化

中子星内部的电子处于高度简并或完全简并的状态,电子磁矩(包括内禀磁矩和朗道反磁矩)的取向不是随机的,而是呈现出极强的磁化行为.考虑了磁化后的磁诱导方程要改写,改写后的方程添加了新的磁场生成项,更重要的改变是等效磁扩散系数变小了(顺磁情况),在临界情况(等效扩散系数等于零),磁场在磁生成项的作用下增加直到抑制机理出现,朗道反磁矩就是在这个时候变得越来越重要.磁场增加的最终结果使中子星局域磁场成为振荡的,对外看来有可能成为磁星. 关键词： 中子星 简并 磁化     

Detection of gravitational waves by electromagnetic radiation

A statistical theory of the ionization — recombination equilibrium of a non-degenerate plasma in a homogeneous magnetic field is given. It is shown that the magnetic field changes the reactive composition if the quanta of the oscillatory electron motion in the magnetic field — which corresponds classically to the electron gyration — are of the order of or larger than the thermal energy,?ω?kT. The ionization may be enhanced or depressed depending on whether the background gas of the plasma is diamagnetic or paramagnetic. Some low temperature experiments, where such an anomalous “magnetic ionization” might be observable, are discussed briefly.     

Singular orbital magnetism of graphene

The origin of the singular diamagnetic susceptibility at the Dirac point is probed through the study of effects of band-gap opening and spatially varying magnetic field. In the presence of a band gap, the susceptibility is nonzero only inside the band gap and exhibits a discrete jump at the band edges down to zero in the conduction and valence bands. The jump height is understood in terms of the pseudo-spin paramagnetism arising from valley degree of freedom. In spatially varying magnetic field with wave vector q, the susceptibility becomes nonzero only in a finite energy region containing the Dirac point, determined by q. This behavior is understood in terms of electronic states numerically calculated in periodic magnetic field.     

Magnetoreflection of s-excitons in cubic ZnSe

The s-exciton spectrum of cubic ZnSe has been studied in magnetic fields up to 9T. The Zeeman splittings and diamagnetic shifts together with the energies of the 1s-, 2s-, 3s-states in zero field yield information about the valence band parameters. The spin coupling scheme of the 1s-state is discussed by means of the experimentally determined longitudinal-transverse splitting and exchange interaction.     

Magnetic moment of quantum cylinders

The magnetic response of a two-dimensional layer rolled into a cylinder and located in a longitudinal magnetic field is examined. The magnetic moment of the degenerate electron gas is studied as a function of the magnetic flux. The shape of the fluctuation maxima is analyzed in detail. It is shown that at zero temperature there are breaks in each period of the change in the magnetic moment. Over this period, a plot of the magnetic moment depends strongly on the ratio of the Fermi energy to the size-confinement energy. In particular, there are no breaks for integral or semi-integral values of the square root of this ratio. Fiz. Tverd. Tela (St. Petersburg) 41, 856–858 (May 1999)     

Diamagnetic susceptibility of spin-triplet ferromagnetic superconductors

We calculate the diamagnetic susceptibility in zero external magnetic field above the phase transition from ferromagnetic phase to phase of coexistence of ferromagnetic order and unconventional superconductivity. For this aim we use generalized Ginzburg-Landau free energy of unconventional ferromagnetic superconductor with spin-triplet electron pairing. A possible application of the result to some intermetallic compounds is briefly discussed.     

Magnetoexciton ground state for heavy- and light-hole excitons in anisotropic semiconductors

Summary We show how to compute the eigenvalues of an anisotropic Schr?dinger equation for light- and heavy-hole excitons in the presence of a magnetic field using a perturbational approach and a simplified deltalike interaction potential. Performing the calculation with a potential approapriate to bulk GaAs crystal we obtain a simple relation between the binding energy at zero field and the diamagnetic shift at low fields.     

电子迥旋加热等离子体及热电子环特性的实验研究

在简单磁镜MM-2中,采用15GHZ大功率迴旋管进行了电子迴旋共振加热(ECRH)实验。结果表明,随充气压强的提高,预电离时间迅速变短。在高气压“C-模式”运行区,等离子体径向密度分布呈马鞍形。在迴旋管输出30kW功率的条件下,适于建立热电子环的气体压力窗为(0.4—1.2)×10^-5Torr。利用一个可移动Laugmuir探针配合反磁测量的简便方法,在中心场为2.95kG时,确定了电子环半径为7cm,环厚约4cm,环的轴向边界由z=±10cm一直延伸到z=±20cm。热电子温度为140—170keV,热电环平均β值为(4—5)％。观测到了由热电子环不稳定性引起的迸发式径向电子逃逸,并同时发生反磁信号跌落。     

Oscillating magnetocaloric effect in quantum nanoribbons

We investigate the oscillating magnetocaloric effect on a diamagnetic nanoribbon, using the model of a quasi-one-dimensional electron gas (Q1DEG) made with a parabolic confinement potential. We obtained analytical expressions for the thermodynamic potential and for the entropy change. The entropy change exhibits the same dependence on field and temperature observed for other diamagnetic systems. The period of the field-oscillating pattern is ~0.1 mT and the temperature of maximum entropy change is ~0.1 K with an applied field of the order of 1 T. An interesting feature of the results is the dependence of the oscillations with the strength of the confinement potential, as well as the possibility to provide a relationship among this last with nanoribbon width. In the limit of null confinement potential our expressions match those for the 2D diamagnetic system.     

Temperature and magnetic field dependencies of Condon domain phase in Lifschitz-Kosevich-Shoenberg approximation

The temperature and magnetic field behavior of non-uniform diamagnetic phase of strongly correlated electron gas at the conditions of the dHvA effect is analyzed. It is shown that in the framework of Lifschitz-Kosevich-Shoenberg approximation the magnetic induction splitting, as well as the range of existence of Condon domains, are characterized by strong dependencies on temperature, magnetic field and impurities of the sample.     

Plasma frequency in a layered electron gas

The equation-of-motion method is applied in the RPA for an electron-hole pair operator in the layered electron gas of Visscher and Falicov. The band of plasma frequencies is obtained at zero temperature.     

Effect of structure anisotropy on low temperature spin dynamics in quantum wells

Spin dynamics of two-dimensional electron gas confined in an asymmetrical quantum well is studied theoretically in the regime where the scattering frequency is comparable with the spin precession frequency due to the conduction band spin splitting. The spin polarization is shown to demonstrate quantum beats. If the spin splitting is determined by both bulk and structural asymmetry mechanisms the beats are damped at zero temperature even in the absence of a scattering. We calculate the decay of spin beats due to the thermal broadening of the electron distribution function and electron scattering. The magnetic field applied along the structure growth axis is shown to increase the frequency of the beats and shift system towards the collision dominated regime.     

Peak effect in single crystal MgB(2) superconductor for H axially c-axis

We have studied the phase diagram of the MgB(2) superconductor using a single crystal for the H parallel c-axis. For the first time we report the existence of peak effect in the screening current in the MgB(2) for the H parallel c-axis. In the magnetic field regime 10相似文献   

On the possibility of a flare-up of discrete exciton absorption structure in n-CdxHg1−xTe crystals in a magnetic field

A discrete absorption peak with an exciton-like behavior was observed to flare up in Cd_xHg_1?xTe with x≈0.3 when a magnetic field H was applied. Its diamagnetic shift, which is replaced at high H by a close-to-linear relationship typical for diamagnetic exciton spectroscopy, and the splitting permit one to evaluate ?_g=0.2579±0.0001 eV and to calculate the band parameters of the material. Evaluation of the fluctuation potential well depth for the electrons and holes suggests, however, a high probability of exciton trapping at potential wells at H = 0 and x ≈ 0.3. Application of a magnetic field above 40 k0e can break the Coulomb bond between the electron and the hole, whereas at lower fields the existence of excitons is possible.     

Magnetic structures and crystal field in the heavy electron materials YbAgGe and YbPtIn

We have examined the magnetic properties of the heavy electron compounds YbAgGe and YbPtIn by ¹⁷⁰Yb M?ssbauer spectroscopy down to 0.1 K, and the crystal field properties of YbAgGe by Perturbed Angular Correlations (PAC) measurements up to 900 K. In YbAgGe, we show that each of the two magnetically ordered phases below 0.8 K involves a specific incommensurate modulation of the Yb moment. An analysis of existing low temperature specific heat data suggests the persistence of fluctuations of the correlated Yb spins down to 0.1 K. The PAC data allow to discriminate among proposed Yb³⁺ crystal field level schemes. In YbPtIn, we show that the low temperature magnetic order phase has an antiferro-para structure, where zero moment Yb ions coexist with large moment ones, and that a 90° moment reorientation occurs at 1.4 K.