Spin-orbit interaction in GaAs wells: From one to two subbands

Abstract

We investigate the Rashba and Dresselhaus spin-orbit (SO) couplings in GaAs quantum wells in the range of well widths w allowing for a transition of the electron occupancy from one to two subbands. By performing a detailed Poisson-Schrödinger self-consistent calculation, we determine all the intra-and inter-subband Rashba (α 1 , α 2 , η) and Dresselhaus (β 1 , β 2 , Γ) coupling strengths. For relatively narrow wells with only one subband occupied, our results are consistent with the data of Koralek et al. [Nature 458 , 610 (2009)], i.e., the Rashba coupling α 1 is essentially independent of w in contrast to the decreasing linear Dresselhaus coefficient β 1 . When we widen the well so that the second subband can also be populated, we observe that α 2 decreases and α 1 increases, both almost linearly with w. Interestingly, we find that in the parameter range studied (i.e., very asymmetric wells) α 2 can attain zero and change its sign, while α 1 is always positive. In this double-occupancy regime of w's, β 1 is mostly constant and β 2 decreases with w (similarly to β 1 for the single-occupancy regime). On the other hand, the intersubband Rashba coupling strength η decreases with w while the intersubband Dresselhaus Γ remains almost constant. We also determine the persistent-spin-helix symmetry points, at which the Rashba and the renormalized (due to cubic corrections) linear Dresselhaus couplings in each subband are equal, as a function of the well width and doping asymmetry. Our results should stimulate experiments probing SO couplings in multi-subband wells.

Spin Blocker Using the Interband Rashba Effect in Symmetric Double Quantum Wells

“…In this paper, we utilize the interband Rashba effect in symmetric double quantum wells (DQWs) [14,[19][20][21][22][23] to generate a bulk spin polarization nonmagnetically, adopting In 0.53 Ga 0.47 As=In 0.52 Al 0.48 As DQWs [24] as a specific example. The interband Rashba effect manifests itself in the off-diagonal matrix element in the 2 × 2 quantum well (QW) space using the bonding and antibonding basis [19,20], which connects subbands with distinct parities and hence operates without the usual Rashba coupling [25][26][27].…”

Topological energy conversion through the bulk or the boundary of driven systems

“…Thus, the frequencies of the drives should be much smaller than the energy scale of the Zeeman energy and the coupling between the two wires, presumably of order of 10 GHz, in the RF range. The Rashba coupling constant u α should be of order of 0.1 meV, which is reasonable in a realistic system [39,40]. The temperature should be presumably of order of 0.1 K so that the broadening of the Fermi surface is small compared to the band gap.…”

“…The boundary energy conversion is then between the two components of the time-dependent magnetic field, with a rate proportional to ω 2 ω 3 , and independent of the length of the chain, as in Eq. (40).…”

“…In particular, we propose to use fermionic atomic gases (e.g. 6 Li, 40 K atoms) in optical lattices to engineer a gauge transformed version of the coupled wires shown in Fig. 4(b).…”

Влияние Электрического Поля На Соотношение Параметров Рашба И Дрессельхауза В Гетероструктурах А-=sup=-Iii-=/Sup=-B-=sup=-v-=/Sup=-

“…Кроме того, константа Дрессельхауза имеет неоднозначную зависимость от номера подзоны размерного квантования и ширины КЯ [22]. Численное решение уравнения (7) позволяет рассчитать параметр Дрессельхауза для разных подзон размерного квантова-ния при различных технологических и геометрических параметрах КЯ с произвольным профилем состава и любым соотношением материалов, составляющих гетероструктуру.…”