Quantum electron lifetime in GaAs quantum wells with three populated subbands

Abstract

The magnetotransport of highly mobile 2D electrons is studied in GaAs single quantum wells with three occupied subbands. The bottoms of the lower two subbands have nearly the same energy while the bottom of the third subband has a much higher energy (E1 ≈ E2 << E3). Magnetointersubband oscillations (MISO) between the i th and j th subbands are observed and obey the relation ∆ij = Ej − Ei = l •hωc, where ωc is the cyclotron frequency and l is an integer. The slight difference in the energies of the lower subbands produces noticeable interference effects in the magnetoresistance. In contrast to the case of two populated subbands, by analyzing the amplitude of each component of the MISOs separately, the quantum lifetime τ (i) q of electrons in i th subband is extracted. The studies show that τ (1) q ≈ τ (2) q = τ (1,2) q. The temperature variation of 1/τ (1,2) q is found to be proportional to T 2 indicating that the electron-electron interaction is the dominant source of the decrease of the electron lifetime at high temperatures. Different temperature dependence of the quantum scattering rate is found in the third subband, δ(1/τ (3) q) ∼ T , which is consistent with the theory of sparsely populated subbands.

Magnetointersubband resistance oscillations in GaAs quantum wells placed in a tilted magnetic field

“…The sensitivity to in-plane magnetic field is due to both a strong Lorent's force, which occurs in studied samples with high electron density, and a weak tunneling between 2D parallel systems. The presented results indicate that the recently observed ambiguity in the MISO amplitude at k=1 is, most likely, related to a small misalignment between the direction of the magnetic field and the normal to 2D sample in different measurements 44,45 .…”

“…where n i and τ (i) q are the electron density and quantum scattering time 46 in the i th subband, ν ij is an effective intersubband transport scattering rate, m is the effective electron mass and ω c = eB ⊥ /m is the cyclotron frequency 28 . This expression has recently been used in systems with two and three populated subbands to extract the quantum scattering rate 1/τ i q [19][20][21][22][23][24]44,45 . The expression indicates that MISO between i th and j th subbands are periodic in inverse magnetic field 1/B ⊥ .…”

“…In Figure 2 the lower panel presents the low frequency content while the upper panel presents the high frequency oscillations, which have been filtered from the curves presented in Fig. 1 45 .…”

“…Shown in Fig. 1 the monotonic background corresponding to the positive quantum magnetoresistance 46,47 has been removed by a procedure reported earlier 45 . However the relatively strong increase of the resistance observed at hω c > ∆ 12 interferes with the low frequency oscillating content making the applied procedure to be quite uncertain there.…”

Resistance oscillations of two-dimensional electrons in crossed electric and tilted magnetic fields

“…At α=0 o the resistance shows low frequency (LF-MISO) and high frequency (HF-MISO) MISO. 38,39 LF-MISO correspond to the scattering between the two lowest symmetric (1) and antisymmetric (2 ) subbands and obey the relation ∆ 12 = khω c . 40 HF-MISO corresponds to scattering between either lowest and the third subband.…”