Magnetic oscillations of resistivity and absorption of radiation in quantum wells with two populated subbands

Abstract

The dynamic ͑ac͒ conductivity tensor of quantum wells with two populated subbands in the presence of a magnetic field perpendicular to the well layer is calculated theoretically. The microscopic theory is based on the Kubo formalism assuming a detailed consideration of elastic scattering of electrons by the random disorder potential with arbitrary correlation length. The results describe the influence of magnetic field on the linear absorption of low-frequency electromagnetic radiation, and demonstrate the existence of magnetic oscillations that survive at high temperatures and whose maxima correspond to absorption of electromagnetic radiation at combined frequencies, determined by both the magnetic field and the subband separation. Different polarizations of the radiation field with respect to the quantum-well layer are considered. Analytical expressions are derived for the case of sufficiently weak magnetic field when the Landau levels are overlapping. Application of the theory to the static ͑dc͒ limit provides a consistent description of the magneto-intersubband oscillations of the resistivity in the systems with two populated subbands.

Quantum electron transport in magnetically entangled subbands

“…Finally a cross comparison of QPMR and classical magnetoresistance in perpendicular magnetic fields shows good mutual agreement with the quantitative theory 14,25,30 and indicates the dominant contribution of the intersubband impurity scattering to the electron transport. An analysis of the MISO amplitude shows significantly less effect of the scattering between subbands, which destroys the overall agreement with theory.…”

“…13,14 At even higher magnetic fields (hω c > kT , corresponding to B ⊥ >0.4 Tesla at T=4.2K) there are SdH oscillations (not shown). In this paper we focus on the low magnetic field (high temperature) regime:hω c ≪ kT , where SdH oscillations are absent.…”

“…Figure 1 presents dependences of the dissipative resistance of 2D electrons on the perpendicular magnetic field, B ⊥ , taken at different angles α between the direction of the total magnetic field, B, and the normal to the 2D layer. At α=0 degree and B ⊥ <0.025 T the magnetoresistance demonstrates a small increase related to classical magnetoresistance 14,26,[29][30][31] . At a higher magnetic field the magnetoresistance slowly increases oscillating at B ⊥ >0.07 T. These oscillations are MISO.…”

“…QPMR is in some respect similar to MISO and reflects the enhancement of the intra-subband impurity scattering due to the quantization of the electron spectrum. 13,14,25 QPMR has been observed in electron systems with two populated subbands 26 and in narrow (13nm) quantum wells with a single subband populated. 27 The later is recently investigated in tilted magnetic fields.…”

“…[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] . At this condition electron elastic scattering on impurities is enhanced due to the possibility of electron transitions between the aligned quantum levels of i th and j th subbands.…”