Lateral-electric-field-induced spin polarization in a suspended GaAs quantum point contact

Abstract

The conductance of a GaAs-based suspended quantum point contact (QPC) equipped with lateral side gates has been experimentally studied in the absence of the external magnetic field. The half-integer conductance plateau (0.5×2e2/h) has been observed when an asymmetric voltage between the side gates is applied. The appearance of this plateau has been attributed to the spin degeneracy lifting caused by the spin-orbit coupling associated with the lateral electric field in the asymmetrically biased QPC. We have experimentally demonstrated that, despite the relatively small g-factor in GaAs, the observation of the spin polarization in the GaAs-based QPC became possible after the suspension due to the enhancement of the electron-electron interaction and the effect of the electric field guiding. These features are caused by a partial confinement of the electric field lines within a suspended semiconductor layer with a high dielectric constant.

Demonstration of electron focusing using electronic lenses in low-dimensional system

“…∆V was kept negative so that the 1D channel shifted towards the primary axis [Fig 1(a)] instead of the tips of the lens, to avoid diffraction at the tips 25 . A short plateau-like feature, as marked by the red arrow in Fig.3(a), below 0.7-anomaly started forming with increasing ∆V similar to previous observations [19][20][21][22][23][24] . We denoted this feature as sub-0.7-anomaly hereafter.…”

Coulomb pairing of electrons in thin films with strong spin-orbit interaction

“…We studied the Coulomb mechanism of electron pairing in low-dimensional structures with a strong Rashba SOI in the case where the e-e interaction is not screened by the environment. This situation is realized in recent experiments on freely suspended 2D structures [24,25]. It attracts growing interest because in this case the e-e interaction effects should be more pronounced.…”

Width dependence of the 0.5 × (2e2/h) conductance plateau in InAs quantum point contacts in presence of lateral spin-orbit coupling

“…The spin-up (spin-down) electrons are the majority spin species on edge I (edge II) and the minority species on edge II (edge I) of the QPC. Since the difference of spin density is anti-symmetric with respect to the middle of the narrow portion of the QPC ( y = w /2), there is no net polarization in the QPC channel 40 . The application of asymmetric bias voltage between the QPC SGs leads to a population of spin-up electrons on the sidewall I, which is larger than the population of spin-down electrons on the sidewall II.…”

“…39 and Pokabov et al . 40 performed conductance measurements on unsuspended and suspended GaAs QPCs with in-plane SGs and the 0.5G o conductance plateau was only observed for the latter. They argued that in their suspended QPCs spin transport mechanism was also governed by LSOC and that the onset of 0.5G o plateau in asymmetrically biased QPCs is due to enhanced e-e interaction, when the QPCs were suspended.…”