Interference of magneto-intersubband and phonon-induced resistance oscillations in single GaAs quantum wells with two populated subbands

Abstract

Low-temperature electron magnetotransport in single GaAs quantum wells with two populated subbands is studied at large filling factors. Magneto-inter-subband (MIS) and acoustic-phonon induced oscillations of the dissipative resistance are found to be coexisting but interfering substantially with each other. The experiments show that amplitude of the MIS-oscillations enhances significantly by phonons, indicating "constructive interference" between the phonon scattering and the intersubband electron transitions. Temperature damping of the quantum oscillations is found to be related to broadening of Landau levels caused by considerable electron-electron scattering.The magnetotransport phenomena in high-mobility modulation-doped semiconductor structures are commonly studied with only one populated subband (E 1 ), because the electron mobility decreases with filling second subband (E2) due to intersubband scattering [1]. The later also gives rise to, so-called, magneto-inter-subband oscillations (MISO) of the dissipative resistance ρ xx [2]. In electron systems with two populated subbands MISO have its maxima in magnetic fields B satisfying to the relation [3][4][5]: ∆ 12 = khω c , where ∆ 12 = E 2 -E 1 is energy separation of the subbands, ω c = eB/m * is cyclotron frequency, m * is effective electron mass and k is a positive integer. Similarly to well-known Shubnikov-de Haas (SdH) oscillations MISO require quantization of the electron spectrum and are periodic in inverse magnetic fields. The electron quantum relaxation time τ q determine the amplitude of the oscillations.Another class of magnetoresistance oscillations in semiconductor structures with high electron mobility emerges at elevated temperatures, when acoustic phonon modes with Fermi momentum become to be populated [6,7]. These oscillations are called phonon-induced resistance oscillations (PIRO). PIRO are result of a modulation of the probability of the electron scattering on phonons with different momentum in quantizing magnetic fields. The dominant phonon-induced scattering between Landau levels changes the direction of the electron motion by 180 degree, providing 2kF variation of the electron wave vector. The modulation, thus, induces resistance oscillations (PIRO) with the period determined by [6]: j = 2k F u s /ω c , where u s is acoustic phonon velocity and j is positive integer.In this paper we show that MISO and PIRO coexist in single GaAs quantum wells with two populated subbands. The coexistence, however, is not a simple sum of the two effects. Our data indicates significant interference between the phonon and the inter-subband scattering, which, to the best of our knowledge, has not been seen yet. The experiment shows that amplitude of the MIS-oscillations enhances significantly by phonons, indicating a nontrivial effect of the phonon scattering on the linewidth of the intersubband quantum transitions. We investigate also effects of the temperature on the amplitude of the quantum oscillations. The oscillations decay at high temperature. The te...

Quantum electron transport in magnetically entangled subbands

“…To analyze the spectrum the obtained eigenvalues of the Hamiltonian are numerated in ascending order using positive integer index l=1,2.... Eqs. (8,9,10) yield the electron spectrum obtained in a rigid electrostatic potential V (z) that provides a good agreement with experimental data. We relate this agreement with a large gap ∆ 12 between subbands indicating strong electrostatic potential V (z) in the system.…”

“…This coupling in due to the Lorentz force and is described by the off-diagonal matrix T mn in Eq. (10). Figure 4 indicates that the application of in-plane magnetic field increases the interval between consecutive intersections of a Landau level, which is the major effect leading to the increase of MISO period.…”

“…[5][6][7][8][9][10] These magneto-inter-subband oscillations (MISO) of the resistance are due to an alignment between Landau levels from different subbands i and j with corresponding energies E i and E j . Resistance maxima occur at magnetic fields at which the gap between the bottoms of subbands, ∆ ij = E i − E j , equals a multiple of the Landau level spacing,hω c : ∆ ij = k ·hω c , where k is an integer [11][12][13][14] .…”

Phase of phonon-induced resistance oscillations in a high-mobility two-dimensional electron gas

“…In contrast to other low-field transport phenomena, such as microwave-induced and Hall fieldinduced [35][36][37][38][39][40][41] resistance oscillations, zero resistance [42][43][44][45][46][47][48][49][50][51][52][53][54] and zero differential resistance [55][56][57] states, PIRO have not received much attention until recently [58][59][60][61][62][63][64][65][66] and several unsolved issues remain.…”

Comment on “Theory of microwave-induced zero-resistance states in two-dimensional electron systems” and on “Microwave-induced zero-resistance states and second-harmonic generation in an ultraclean two-dimensional electron gas”

“…12 have shown that in their experiment the temperature dependence originated from electron-electron interactions modifying the single particle lifetime [15,16]. The same mechanism was later confirmed in studies of the temperature dependence of other related phenomena [17][18][19][20].…”