Theory of g-factor enhancement in narrow-gap quantum well heterostructures

We report on the study of the exchange enhancement of the g-factor in the two-dimensional (2D) electron gas in n-type narrow-gap semiconductor heterostructures. Our approach is based on the eight-band k?p Hamiltonian and takes into account the band nonparabolicity, the lattice deformation, the spin-orbit coupling and the Landau level broadening in the δ-correlated random potential model. Using the 'screened' Hartree-Fock approximation we demonstrate that the exchange g-factor enhancement not only shows maxima at odd values of Landau level filling factors but, due to the conduction band nonparabolicity, persists at even filling factor values as well. The magnitude of the exchange enhancement, the amplitude and the shape of the g-factor oscillations are determined by both the screening of the electron-electron interaction and the Landau level width. The 'enhanced' g-factor values calculated for the 2D electron gas in InAs/AlSb quantum well heterostructures are compared with our earlier experimental data and with those obtained by Mendez et?al (1993 Phys.?Rev.?B 47 13937) in magnetic fields up to 30?T.     

Magnetospectroscopy of double HgTe/CdHgTe QWs with inverted band structure in high magnetic fields up to 30 T

Magnetoabsorption in far and mid IR ranges in double HgTe/CdHgTe quantum wells with inverted band structure has been studied in high magnetic fields up to 30 T. Numerous intraband and interband transitions have been revealed in the spectra and interpreted within axial 8 × 8 k·p model. Splitting of dominant magnetoabsorption lines resulting from optical transitions from hole-like zero-mode Landau level has been discovered and discussed in terms of a built-in electric field and collective phenomena.     

Terahertz Spectroscopy of Two-Dimensional Semimetal in Three-Layer InAs/GaSb/InAs Quantum Well

JETP Letters - The features of terahertz photoluminescence and magnetoabsorption in magnetic fields up to 16 T in threelayer InAs/GaSb/InAs quantum wells with a band structure corresponding to a...     

Exchange interaction effects in electron spin resonance: Larmor theorem violation in narrow-gap quantum well heterostructures

We report a theoretical study of the exchange interaction effects in the electron spin resonance (ESR) in n-type narrow-gap quantum well (QW) heterostructures. Using the Hartree-Fock approximation, based on the eight-band k?p Hamiltonian, the many-body correction to the ESR energy is found to be nonzero, providing theoretical evidence of Larmor theorem violation in symmetric narrow-gap QWs. We predict the exchange enhancement of the ESR g-factor and its divergence in low magnetic fields. The 'enhanced' ESR g-factor and quasiparticle g-factor, measured in magnetotransport, coincide at even-valued filling factors of the Landau levels in moderate and quantizing magnetic fields.     

Origin of Structure Inversion Asymmetry in Double HgTe Quantum Wells

JETP Letters - The density dependences of the splitting values of the dominant magneto-absorption lines in undoped p-type double HgTe/CdHgTe quantum wells are studied. An analysis of the splitting...     

Effects of the Electron—Electron Interaction in the Magneto-Absorption Spectra of HgTe/CdHgTe Quantum Wells with an Inverted Band Structure

JETP Letters - Magneto-absorption in HgTe/CdHgTe quantum wells with an inverted band structure in magnetic fields up to 30 T has been studied. It has been shown that the positions of...     

The effect of exchange interaction on quasiparticle Landau levels in narrow-gap quantum well heterostructures

Using the 'screened' Hartree-Fock approximation based on the eight-band k·p Hamiltonian, we have extended our previous work (Krishtopenko et al 2011 J. Phys.: Condens. Matter 23 385601) on exchange enhancement of the g-factor in narrow-gap quantum well heterostructures by calculating the exchange renormalization of quasiparticle energies, the density of states at the Fermi level and the quasiparticle g-factor for different Landau levels overlapping. We demonstrate that exchange interaction yields more pronounced Zeeman splitting of the density of states at the Fermi level and leads to the appearance of peak-shaped features in the dependence of the Landau level energies on the magnetic field at integer filling factors. We also find that the quasiparticle g-factor does not reach the maximum value at odd filling factors in the presence of large overlapping of spin-split Landau levels. We advance an argument that the behavior of the quasiparticle g-factor in weak magnetic fields is defined by a random potential of impurities in narrow-gap heterostructures.     

HgTe/CdHgTe double quantum well with a spectrum of bilayer graphene and peculiarities of its magnetotransport

Free expansion of Bose–Einstein condensates of rubidium atoms at finite temperatures has been analyzed experimentally and theoretically. It has been shown that the interaction between condensed and noncondensed atoms is manifested most clearly by a decrease in the density of atoms in the center of the expanding cloud as compared to the theoretical prediction for a pure condensate.     

Magnetoabsorption of Dirac Fermions in InAs/GaSb/InAs “Three-Layer” Gapless Quantum Wells

Subablative exposure of tightly focused visible-range femtosecond laser pulses on a thin translucent nanocrystalline copper(I) oxide on a silica glass substrate results not only in its annealing (resolidification), but apparently also in reduction of copper ions to the metallic state via single-photon absorption and the following thermal decomposition (disproportioning). Partial or complete ablation of the film within the laser focal spot and also its subablative optically contrast modification through formation of colloidal nanoparticles or annealing (resolidification) make it possible to consider this material in the thin-film form as a novel optical platform for direct laser writing of vis-IR metasurfaces and thin-film sensing plasmonic and all-dielectric nanostructures.     

Polarization-Sensitive Fourier-Transform Spectroscopy of HgTe/CdHgTe Quantum Wells in the Far Infrared Range in a Magnetic Field

Spectra of magnetoabsorption and Faraday rotation in HgTe/CdHgTe heterostructures with single and double quantum wells in high magnetic fields up to 11 T have been studied by the Fourier-transform spectroscopy method. The study of Faraday rotation spectra makes it possible to determine the sign of resonance circular polarization of transitions between Landau levels of carriers, which allows identifying observed intraband and interband transitions in the far and middle infrared ranges.