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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...

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 ...