Effect of electron-electron scattering on magnetointersubband resistance oscillations of two-dimensional electrons in GaAs quantum wells

Abstract

The low-temperature(4.2 < T < 12.5 K) magnetotransport (B < 2 T) of two-dimensional electrons occupying two subbands (with energy E 1 and E 2 ) is investigated in GaAs single quantum well with AlAs/GaAs superlattice barriers. Two series of Shubnikov-de Haas oscillations are found to be accompanied by magnetointersubband (MIS) oscillations, periodic in the inverse magnetic field. The period of the MIS oscillations obeys condition ∆ 12 =(E 2 −E 1 )=k · hω c , where ∆ 12 is the subband energy separation, ω c is the cyclotron frequency, and k is the positive integer. At T=4.2 K the oscillations manifest themselves up to k=100. Strong temperature suppression of the magnetointersubband oscillations is observed. We show that the suppression is a result of electron-electron scattering. Our results are in good agreement with recent experiments, indicating that the sensitivity to electron-electron interaction is the fundamental property of magnetoresistance oscillations, originating from the second-order Dingle factor.The Landau quantization in quasi-two-dimensional (2D) electron systems (with two or more occupied subbands) manifests itself in two or more sets of Landau levels. Resonance transitions of electrons between Landau levels corresponding to different two-dimensional subbands [1,2] causes the so-called magnetointersubband (MIS) oscillations of the resistance ρ xx [3][4][5]. The interaction between two subbands can be also significant for other phenomena such as cyclotron resonance [6]. The position of the maxima of the MIS oscillations obeys the condition ∆ 12 =E 2 −E 1 =k · hω c , where ∆ 12 is the intersubband energy gap, E i is the energy of the bottom of ith subband, ω c is the cyclotron frequency, and index k is the positive integer. The oscillations, similar to well-known Shubnikov-de Haas (SdH) oscillations, are periodic in the inverse magnetic field and appear in classically strong magnetic fields. The amplitude of SdH oscillations is limited by the broadening of Landau levels due to scattering and by thermal broadening of the Fermi distribution. With increasing temperature the thermal broadening of the Fermi distribution becomes the dominant factor, limiting the amplitude of SdH oscillations. MIS oscillations are significantly less sensitive to the electron distribution and their amplitude is predominantly determined by a quantum relaxation time τ q [4,5].MIS oscillations were recently observed in GaAs double quantum wells with AlAs/GaAs superlattice barriers with roughly equal electron densities in subbands (n 1 ≈ n 2 ) [7][8][9][10]. The quantum lifetimes of the electrons in subbands was also approximately equal (τ q1 ≈ τ q2 ) [11]. In the general case of two populated subbands the amplitude of the MIS oscillations of the resistance ∆ρ MISO depends on the sum of the quantum scattering rates in each subband [4,5] ),where 1/τ qi and n i are the quantum scattering rate and electron density in ith subband, and m is electron band mass. Parameter ν 12 is an effective intersubband scattering rate [5].In this ...

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.…”

“…In contrast at α=0 degree the observed dependence deviates significantly from a straight line that has been seen previously. 9 An attractive mechanism, which may lead to these deviations is a non-parabolic spectrum of 2D electrons due to the presence of the valence band. The non-parabolicity makes the quantized spectrum to be not periodic with the energy leading to a breakdown of the perfect spectral overlap between subbands at MISO maximums described by Eq.(1).…”

“…[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] .…”

Quantum lifetime of two-dimensional electrons in a magnetic field

“…The overheating may create very peculiar electron distributions [24] and is a restriction of this method. In another set of experiments the temperature dependence of the quantum lifetime τ q is extracted from the amplitude of magneto-intersubband oscillations (MISO) in double GaAs quantum wells [56] and in wide GaAs quantum wells with two occupied subbands [57]. This method works in the linear response regime (at thermal equilibrium) but requires two sets of Landau levels and, therefore, does not work for common electron systems with only one populated subband(see also Ref.…”

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

“…1a), discloses two peaks corresponding to SdH oscillations (with frequencies f 1 and f 2 ) and one peak corresponding to MISO (with frequency f MISO ≅ f 1 -f 2 ) [15]. Electron concentration in subbands was calculated from frequencies f 1 At higher magnetic field B > 0.8 T ( 1/B<1.25 Т -1 ) the amplitude of MIS-oscillations decreases significantly and deviates from the theory.…”