Quantum limit in a quasi-one-dimensional conductor in a high tilted magnetic field

Recently, we have suggested Fermi-liquid–non-Fermi-liquid angular crossovers that may exist in quasi-one-dimensional (Q1D) conductors in high tilted magnetic fields (see A. G. Lebed, Phys. Rev. Lett. 115, 157001 (2015)). All calculations in the Letter were done by using the quasiclassical Peierls substitution method, whose applicability in high magnetic fields was questionable. Here, we solve a fully quantum mechanical problem and show that the main qualitative conclusions of the work cited above are correct. In particular, we show that in high magnetic fields, applied along one of the two main crystallographic axis, we have 2D electron spectrum, whereas, for directions of high magnetic fields far from the axes, we have 1D electron spectrum. The latter is known to promote non-Fermi-liquid properties. As a result, we expect the existence of Fermi-liquid–non-Fermi-liquid angular crossovers or phase transitions. Electronic parameters of Q1D conductor (Per)₂Pt(mnt)₂ show that such transitions can appear in feasible high magnetic fields of the order of H ? 20–25 T.     

Quantum oscillations in screening in a two-dimensional electron gas

The static dielectric constant of a two-dimensional electron gas is studied as a function of the strength of a dc magnetic field applied normal to the plane of the electron gas. At high temperatures $\text{(kT ?}\text{h}\text{?}\text{ω}{}_{\mathrm{c}}\text{)}$ the static dielectric function is independent of magnetic field, and for long wavelengths is given by ? ? ?₀ + 2n_vme²/q, where ?₀ is the background dielectric constant and n_v is the valley degeneracy. At low-temperatures, quantum oscillations become important and dramatically modify the screening.     

Self-consistent theory of screening in a two dimensional electron gas under strong magnetic field

The dielectric response of a two dimensional electron gas under a strong transverse magnetic field is obtained within a self-consistent procedure in which the broadening of Landau levels due to collisional damping from the impurities both determines and is determined by the static dielectric function of the system. The dielectric function is evaluated in random phase approximation with the impurity scattering treated in a self-consistent Born approximation. Explicit results are presented for the zero temperature, extreme quantum limit. It is found that this “no parameter” theory is in good qualitative agreement with experimental results for the broadening as extracted from magnetotransport data.     

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.     

Interacting electron gas in a strong magnetic field

The density response function of an electron gas in a strong magnetic field shows logarithmic singularities due to scattering across the Fermi surface. We analyze the parquet equations for the vertex function in leading logarithmic order for a general interaction potential. The parquet equations are solved for a special interaction potential (Schulz and Keiter model). The divergence of the density response function at extremely high fields is discussed in connection with a possible transition to a Wigner lattice.     

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.     

Hydrodynamic theory of electron transport in a strong magnetic field

The mode coupling contribution to the transverse transport coefficients of a three-dimensional one-component plasma in a strong external magnetic field is calculated. For very strong fields it is found that the tagged particle diffusion rate, the thermal diffusion rate, and the coefficient of viscosity in the plane orthogonal to the field have a Bohm-like B ^–1 behavior. The mode coupling mechanism responsible for such an effect is always one that involves the finite-frequency upper hybrid modes.     

Linear response functions of a quasi-one-dimensional electron gas

The predictions for density-density-type response functions of a quasi-one dimensional electron gas are compared in detail for various models (Hubbard and Tomonaga model) and for various approximations (Monte-Carlo calculations, RPA and extended RPA). It is shown that RPA does not lead to intrinsic contradictions for electron densities larger than 1.5 inverse exciton Bohr radii. Even in this high-density regime local field corrections enhance spin- and density susceptibilities significantly.     

CDW instability of electron gas in a strong magnetic field

It is shown that within the Hartree-Fock approximation the electron gas in the quantum limit of a strong magnetic field has an instability as the temperature is lowered toward the charge density wave state with an wave-vector which has finite components in the directions not only parallel but also perpendicular to the field. The critical temperature, T_c, is estimated under the assumption of T_c??_F?ω_c, where ?_F and ω_c are the Fermi energy of the non-interacting system and the cyclotron frequency respectively.     

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.