Intrinsic bistability in quantum point contacts with in-plane side gates

Abstract

We study the onset of intrinsic bistability and accompanying hysteresis in a single quantum point contact (QPC) with in-plane side gates in the presence of lateral spin-orbit coupling. The hysteresis in the conductance versus common gate voltage applied to the two side gates exists only if the narrow portion of the QPC is long enough. The hysteresis is absent if the effects of electron-electron interaction are neglected but increases with the strength of the electron-electron interaction. The hysteresis appears in the region of conductance anomalies, i.e., less than 2e 2 /h, and is due to multistable spin textures in these regions.

Hysteresis in the conductance of asymmetrically biased GaAs quantum point contacts with in-plane side gates

“…Recently, we reported a theoretical investigation of the onset of hysteresis of asymmetrically biased GaAs QPC with in-plane side gates in the presence of lateral spin-orbit coupling (LSOC) [23]. We showed that the hysteresis in the conductance versus common gate bias applied to the two side gates exists only if the narrow portion of the QPC is long enough.…”

“…The hysteresis appears in the region of conductance anomalies, i.e., less than 2e 2 /h, and is due to multistable spin textures in these regions [23]. Hereafter, we used the NEGF approach to investigate the influence of dangling bond scattering on the conductance of a GaAs with in-plane side gates which has been shown to have a strong influence on the location of the conductance anomalies [26].…”

“…(1). At the interface between the rectangular region of size w 2 ×l 2 and vacuum, the conduction band discontinuities at the bottom and the top interface were modeled using a smooth conductance band change spread over a range d selected to be in the nm range to represent a gradual variation of the conduction band profile from the inside of the quantum wire to the vacuum region [23][24][25]. A similar grading was also used along the walls going from the wider part of the channel to the central constriction of the QPC (Fig.4).…”

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

“…These results are in agreement with NEGF simulations which show that the conductance plots versus common gate voltage applied to a QPC SGs reveal the presence of single or multiple hysteresis loops when varying the QPC dimensions and biasing conditions 57,58 . The following features were predicted by NEGF simulations: (a) hysteresis in the conductance plots is present only for sufficiently long QPCs and the e-e interaction in the channel must be strong enough; (b) The size of the hysteresis loops depends both on the polarity and magnitude of the asymmetric bias between the side gates, Δ V G , and also on the magnitude of the e-e interaction; (c) The hysteresis loops are sensitive to the presence of dangling bonds on the QPC sidewalls 59 . We also used NEGF simulations to illustrate how to fine tune the location of the 0.5 G 0 and the onset of hysteresis loops in four-gate QPCs when LSOC is present in the channel 60 .…”

“…We also used NEGF simulations to illustrate how to fine tune the location of the 0.5 G 0 and the onset of hysteresis loops in four-gate QPCs when LSOC is present in the channel 60 . The rich plethora and sensitivity of the hysteresis loops is a fingerprint of the wide variety of metastable spin textures accompanying the onset of a net spin polarization and the appearance of conductance anomalies in the QPC constriction 58,59 . The observation of hysteresis loops is yet another indirect evidence for the onset of spontaneous spin polarization in the QPC constriction.…”