Intersubband-induced spin-orbit interaction in quantum wells

Abstract

Recently, we have found an additional spin-orbit (SO) interaction in quantum wells with two subbands [Phys. Rev. Lett. 99, 076603 (2007)]. This new SO term is non-zero even in symmetric geometries, as it arises from the intersubband coupling between confined states of distinct parities, and its strength is comparable to that of the ordinary Rashba. Starting from the $8 \times 8$ Kane model, here we present a detailed derivation of this new SO Hamiltonian and the corresponding SO coupling. In addition, within the self-consistent Hartree approximation, we calculate the strength of this new SO coupling for realistic symmetric modulation-doped wells with two subbands. We consider gated structures with either a constant areal electron density or a constant chemical potential. In the parameter range studied, both models give similar results. By considering the effects of an external applied bias, which breaks the structural inversion symmetry of the wells, we also calculate the strength of the resulting induced Rashba couplings within each subband. Interestingly, we find that for double wells the Rashba couplings for the first and second subbands interchange signs abruptly across the zero bias, while the intersubband SO coupling exhibits a resonant behavior near this symmetric configuration. For completeness we also determine the strength of the Dresselhaus couplings and find them essentially constant as function of the applied bias.Comment: 16 pages, 12 figure

General theory of Zitterbewegung

“…[33] using a different approach. For many systems [5,[7][8][9][10][11][12][13][14][15][16][19][20][21][22][23][24][25][26][27][28][29][30][31][32][33] the Hamiltonian can be written in a quite general form:…”

Energy spectra for quantum wires and two-dimensional electron gases in magnetic fields with Rashba and Dresselhaus spin-orbit interactions

“…As shown experimentally, the Rashba coupling strength can be tuned via proper gating of the structure 12,13 , which makes the Rashba interaction very appealing for potential technological applications involving spin control. More recently, yet a new type of spin-orbit interaction has been found in symmetric two-dimensional quantum structures with two subbands: the inter-subbandinduced spin-orbit coupling 14,15 . Interestingly, this new spin-orbit interaction gives rise to non-zero intrinsic spin Hall effect 16 .…”

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].…”

“…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]. Because of its novelty, the interband Rashba effect has been providing intriguing playgrounds for physics in various contexts [28,29].…”