Spin-wave excitations and electron spin resonance in symmetric and asymmetric narrow-gap quantum wells

Abstract

We report a theoretical study of spin-wave excitations and electron spin resonance (ESR) in a perpendicular magnetic field in $n$-type narrow-gap quantum well (QW) heterostructures. Using the Hartree-Fock approximation, based on the 8 $\ifmmode\times\else\texttimes\fi{}$ 8 k$\ifmmode\cdot\else\textperiodcentered\fi{}$p Hamiltonian, the many-body corrections to the ESR energy are found to be nonzero in symmetric and asymmetric QWs. We demonstrate a significant enhancement of the ESR energy in the asymmetric QWs, induced by the Bychkov-Rashba spin splitting and exchange interaction in weak and moderate magnetic fields, as well as the exchange-induced divergence of the ESR $g$ factor in the symmetric QWs in weak magnetic fields. We calculate the spin-wave dispersions at odd-valued filling factors of the Landau levels for different values of 2D electron concentration in the symmetric and asymmetric InAs/AlSb QW heterostructures. We predict a gap for the long wavelength spin-wave excitations in symmetric and asymmetric narrow-gap QWs induced by the spin-orbit interaction and subband nonparabolicity. The many-body renormalization of electron spin resonance energies in HgTe/CdHgTe QWs is also qualitatively discussed.