Двумерные электроны низкой плотности в магнитном поле

The photoluminescence spectrum from the two-dimensional low density electrons with the localized valence-band holes in magnetic field is studied. The ground state is considered as Wigner crystal ore the strongly correlated electron system. For the quantum Wigner crystal the Landau levels for vacancions (quasiholes appearing in the process of photoluminescence) are calculated in the quasiclassical approximation. The spectrum of single-particle excitations for a triangular lattice in the nearest-neighbor approximation is used. It is found that Landau levels for vacancions depend unusually on magnetic field. For the electron system with strong Coulomb interaction the Mahan exciton effect in the photoluminescence for the two-dimensional electrons in magnetic field is considered.

Magneto-Optical properties in thin film Topological insulators with quadratic momentum term

In this work we investigate the influence of quadratic in momentum term (Schrodinger term) on magneto-transport properties of thin film topological insulators. The Schrodinger term modifies the Dirac cones into an hourglass shape which results in inter and intraband Landau levels crossings. Breaking of the particle-hole symmetry in Landau level spectrum in the presence of k2 term leads to asymmetrical density of states profile. We calculate collisional and Hall conductivity for mixed Dirac-Schrodinger system in linear response regime and show oscillatory behavior in collisional con- ductivity, while Zeeman and hybridization terms provide a doubly split peak structure in collisional conductivity for the case m/me → ∞. We calculate Hall conductivity analytically and show that for mixed system filling factor is not symmetric about Fermi energy unlike symmetic plateaus for pure Dirac case.

Magneto-optic signatures in the gapped Dirac semimetal with mixed linear and parabolic dispersions of ZrTe5

In this paper, we give a systematic theoretical study on the Landau levels (LLs) and magneto-optical conductivity Re(σαα) in a gapped Dirac semimetal model with mixed linear and parabolic dispersions under a magnetic field, which was recently proposed by Jiang et al. [Phys. Rev. Lett. 125, 046403 (2020)] to explain the experimental magnetoinfrared spectroscopy in the three-dimensional ZrTe5 crystal. We find that the strong magnetic field can drive the LLs become noninverted and thus the strong topological insulator phase in ZrTe5 turns to be a trivial insulator. In the different magnetic field regions, the density of states and Re(σαα) can exhibit distinct signatures. Moreover, when the magnetic field is weak, a qualitative relation in Re(σzz) between the peaks at the saddle points is revealed as Re(σzz ζn) >Re(σzz Γ) , which is in good agreement with the experiment.

Relativistic Landau quantization in non-uniform magnetic field and its applications to white dwarfs and quantum information

We investigate the two-dimensional motion of relativistic cold electrons in the presence of `strictly’ spatially varying magnetic fields satisfying, however, no magnetic monopole condition. We find that the degeneracy of Landau levels, which arises in the case of the constant magnetic field, lifts out when the field is variable and the energy levels of spin-up and spin-down electrons align in an interesting way depending on the nature of change of field. Also, the varying magnetic field splits Landau levels of electrons with zero angular momentum from positive angular momentum, unlike the constant field which only can split the levels between positive and negative angular momenta. Exploring Landau quantization in non-uniform magnetic fields is a unique venture on its own and has interdisciplinary implications in the fields ranging from condensed matter to astrophysics to quantum information. As examples, we show magnetized white dwarfs, with varying magnetic fields, involved simultaneously with Lorentz force and Landau quantization affecting the underlying degenerate electron gas, exhibiting a significant violation of the Chandrasekhar mass-limit; and an increase in quantum speed of electrons in the presence of a spatially growing magnetic field.

Geometric characterization of anomalous Landau levels of isolated flat bands

According to the Onsager’s semiclassical quantization rule, the Landau levels of a band are bounded by its upper and lower band edges at zero magnetic field. However, there are two notable systems where the Landau level spectra violate this expectation, including topological bands and flat bands with singular band crossings, whose wave functions possess some singularities. Here, we introduce a distinct class of flat band systems where anomalous Landau level spreading (LLS) appears outside the zero-field energy bounds, although the relevant wave function is nonsingular. The anomalous LLS of isolated flat bands are governed by the cross-gap Berry connection that measures the wave-function geometry of multi bands. We also find that symmetry puts strong constraints on the LLS of flat bands. Our work demonstrates that an isolated flat band is an ideal system for studying the fundamental role of wave-function geometry in describing magnetic responses of solids.