arXiv subjects
Publications and source records attributed to K. A. Chao.
We investigate the effects of compressible and incompressible states on the FIR-absorption of quantum wires and dots in a homogeneous perpendicular magnetic field. The electron-electron interaction is treated in the Hartree approximation at a finite low temperature. The calculated dispersion of the collective excitations reproduces several experimental results.
We investigate the evolution of the interaction of the magnetoplasmon resonance with the harmonics of the cyclotron resonance as the confinement of an electron gas in a quantum wire increasingly deviates from the parabolic case. The occurrence of the Bernstein modes is observed in a time-dependent Hartree model of a two-dimensional electron gas in a single quantum wire.
We have used the Hartree-Fock Random Phase Approximation (HF-RPA) to study the interacting electron gas in a quantum wire. The spectra of intersubband spin-flip excitations reveal a considerable red shift with respect to single-particle HF energies. That signals on appearance of collective intersubband spind-density excitations due to the exchange interaction. The long wavelength dispersions of the intrasubband collective spin-density excitations are linear, but the sound velocities are renormalised due to the exchange interaction and screening. The in-phase intrasubband charge-density excitation has the long wavelength form $q[-\ln(q)]^{1/2}$. We found good qualitative agreement of our results with experimental observations.
We have analyzed the effect of electron-LO phonon interaction in a double-barrier resonant tunneling structure under a magnetic field {\bf B} applied parallel to the tunneling current. While the low temperature anti-crossing phenomenon has already been investigated, here we study the phonon absorption resonant magnetotunneling at finite temperatures. The Matsubara technique is used to sum up resonant diagrams of higher orders, and the result is selfconsistently renormalized. The phonon absorption tunneling spectrum has been calculated numerically. The result shows that the phonon-absorption process produces two broad inelastic wings on the main elastic tunneling peak, the strength of which is sensitive to the resonant condition, and grows with increasing temperature. The width of the inelastic wings are proportional to $B^{1/2}$. This is in contrast to the appearance of anti-crossing in the phonon emission tunneling process. The difference is due to the fact that the phonon emission is a coherent process, while the absorption is a typical incoherent process since absorbed real phonons have random phases.