Collective modes and the far-infrared absorption of the two-dimensional electron gas in a periodic quantizing magnetic field

We investigate the far-infrared (FIR) absorption of a two-dimensional electron gas in a periodically modulated quantizing magnetic field. The magnetic field varies along only one spatial direction and the external time-dependent electric field is linearly polarized along that axis. The mutual Coulomb interaction of the electrons is treated self-consistently in the ground state and in the absorption calculation within the Hartree approximation. The effects of the magnetic material on top of the heterostructure as a grating coupler is included in the time-dependent incident FIR electric field. We show that, similar to an electric modulation, the absorption can be directly correlated to the underlying electronic energy bands. In addition, the magnetic modulation leads to absorption spectra with a richer structure due to the quite different static response of the electron density to the modulation.     

Magnetoresistance of a two-dimensional electron gas in a parallel magnetic field

The conductivity of a two-dimensional electron gas in a parallel magnetic field is calculated. We take into account the magnetic-field-induced spin-splitting, which changes the density of states, the Fermi momentum, and the screening behavior of the electron gas. For impurity scattering, we predict a positive magnetoresistance for low electron density and a negative magnetoresistance for high electron density. The theory is in qualitative agreement with recent experimental results found for Si inversion layers and Si quantum wells.     

Wigner function of a two-dimensional electron gas in a magnetic field

The Wigner function of a two-dimensional electron gas in an arbitrary magnetic field perpendicular to the plane in which the electrons are confined is constructed rigorously. The function is useful in taking various statistical averages and illuminates the roles played by the hyperbolic functions of the field which appear in the expressions of the susceptibility and other physical quantities.     

Compressibility of a two-dimensional electron gas in a parallel magnetic field

The thermodynamic compressibility of a two-dimensional electron system in the presence of an in-plane magnetic field is calculated. We use accurate correlation energy results from quantum Monte Carlo simulations to construct the ground state energy and obtain the critical magnetic field B_c required to fully spin polarize the system. Inverse compressibility as a function of density shows a kink-like behavior in the presence of an applied magnetic field, which can be identified as B_c. Our calculations suggest an alternative approach to transport measurements of determining full spin polarization.     

Analytical thermodynamical properties of a two-dimensional electron gas in a magnetic field

Analytical expressions for the thermodynamical properties of a two-dimensional electron gas in a perpendicular magnetic field are derived.This is accomplished by first deriving the general expression for the thermodynamical potential,and then employing this result to obtain the corresponding expression for the two-dimensional gas.The chemical potential and magnetization are studied as a function of temperature and magnetic field,and shown to be in agreement with prior work.It is also shown that the results are close to those obtained by assuming a Gaussian density of states for the Landau levels.     

Optical phonons of Rare-Earth halides in a magnetic field

A theory is developed which explains the observed magnetic field splitting of doubly degenerateE-phonons in Rare Earth Chlorides. It is based on first and second order magnetoelastic interactions. Quantitative calculations are done for CeCl₃ for which the field dependence of the splitting is derived and estimates of the coupling constants are given.Furthermore we propose a mechanism for the observed reduction of the phononlinewidth in a magnetic field.     

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 $\text{μ}{}^2{}_{\mathrm{B}}\text{2π}$.     

Hartree-Fock solution of CDW of two-dimensional electron gas in magnetic field

Temperature dependence of the amplitude of the charge density wave of two-dimensional electron gas in strong magnetic field is calculated within Hartree-Fock approxiimation. The density of states is investigated, too, and it is shown that there is not an energy gap at Fermi level when the lowest Landau level is half filled.     

Optical manipulation of nuclear spin by a two-dimensional electron gas

Conduction electrons are used to optically polarize, detect, and manipulate nuclear spin in a (110) GaAs quantum well. Using optical Larmor magnetometry, we find that nuclear spin can be polarized along or against the applied magnetic field, depending on field polarity and tilting of the sample with respect to the optical pump beam. Periodic optical excitation of the quantum-confined electron spin reveals a complete spectrum of optically induced and quadrupolar-split nuclear resonances, as well as evidence for Deltam = 2 transitions.     

Spin-dependent transport in a magnetic two-dimensional electron gas

Magneto-transport and magneto-optical probes are used to interrogate spin-dependent transport in magnetic heterostructures wherein a two dimensional electron gas (2DEG) is exchange-coupled to local moments. At low temperatures, the significant s–d exchange-enhanced spin splitting in these “magnetic” 2DEGs is responsible for the observation of unusual transport properties such as a complete spin polarization of the gas at large Landau level filling factors and a pronounced, non-monotonic background magneto-resistance. Magneto-transport measurements of gated samples performed in a parallel field geometry are used to systematically study the variation of the magneto-resistance with sheet concentration, yielding new insights into the dependence of spin transport on the Fermi energy of the majority spin carriers.     

Longitudinal dielectric behavior of a harmonically bound two-dimensional electron gas in a uniform magnetic field

We have employed random-phase approximation to determine the inverse dielectric function for a harmonically confined two-dimensional electron gas in a magnetic field. We examine the plasmon dispersion relation and show the results for the variation of plasmon frequency with the magnetic field strength and confinement energy.     

Distribution functions for a two-dimensional non-interacting quantum electron gas in an external magnetic field

The exact n-body distribution functions are calculated for a two-dimensional, non-interacting quantum electron gas in an external magnetic field for any temperature and density. At low tempertures and filled lowest Landau level (LLL), these functions are identical to the exact distribution functions obtained by Jancovici [1981, Phys. Rev. Lett., 46, 386] for the classical two-dimensional one-component plasma (2DOCP) at the special plasma parameter Γ = 2, thus establishing that the 2DOCP provides an exact classical Boltzmann factor which describes the ideal LLL quantum state associated with the integral quantum Hall effect.     

Raman scattering from a two-dimensional electron gas in a weakly and periodically modulated magnetic field

An analysis of light scattering from a two-dimensional electron gas (2DEG) subject to aweak periodicmagnetic modulation of strengthB_mand to a perpendicular uniform magnetic fieldBof arbitrary strength is presented. Raman spectra are calculated for (i) electron inter-Landau-level transitions, which result in a Raman shift ∼  2ω_c, and (ii) inter-Landau-level collective electron excitations at a hybridized magnetoplasmon frequency and at anewlow-frequency, intra-Landau-level plasmon mode induced by the modulation. The dependence of the Raman cross sections on the strength ofBandB_mis assessed. The effect of a weakB_mon the Raman spectrum is similar to that of a weak electric modulation but the signals from the magnetically modulated 2DEG are much stronger. The combined effect of the electric and magnetic modulations is also considered.     

Two-dimensional electron gas in a periodic magnetic field

We study the energy spectrum and electronic properties of a two-dimensional (2D) spinless electron gas in a periodic magnetic field which has the symmetry of a triangular lattice. We show that the energy bands depend strongly on the value of the magnetic field. For large field the low-energy electrons are localized on closed rings where the magnetic field vanishes. This results in the appearance of persistent currents around these rings. We also calculate the intrinsic Hall conductivity, which is quantized when the Fermi level is in a gap.