Bound Electron Pairs Formed by the Spin–Orbit Interaction in 2D Gated Structures

Abstract

The bound electron pairs (BEPs) arising due to the pair spin–orbit interaction (PSOI) in 2D structures are explored with a gate that allows the BEPs to be manipulated. The gate breaks the in‐plane reflection symmetry of the pair Coulomb field and creates a one‐particle Rashba spin–orbit interaction. It is found that the normal component of the electric field substantially affects the BEPs but the key role in forming the BEPs belongs to the in‐plane component. The ground state of a BEP with zero total momentum, which is doubly degenerate in the absence of the gate, splits into two states. One of them is tunable by varying the gate voltage, whereas the other is on the contrary robust. The tunable BEP has a higher binding energy which grows as the gate voltage increases, with its orbital and spin structure changing continuously. At large negative voltage, the tunable BEP decays. The orbital and spin structure of the robust BEP does not depend on the gate voltage. Its energy level crosses the conduction band bottom at high gate voltage of any polarity, but the robust BEP remains bound and localized even when in continuum.

Spin-Current Modulation in Hexagonal Buckled ZnTe and CdTe Monolayers for Self-Powered Flexible-Piezo-Spintronic Devices

“…Interestingly, the electric field along the x-direction (E x ) has no effect, while the same along the ydirection (E y ) is found to induce Rashba-type spin splitting at the valence band. 44 The band structure of the CdTe monolayer at E y = 0.4 V/Å is plotted and provided in Figure S3. Figure 4 depicts 2D energy contour plots of CBM, where spin components S x , S y , and S z are projected.…”

“…Also, it can be clearly observed from Table that the orbital composition of band edges in ZnTe and CdTe monolayers is similar. Interestingly, the electric field along the x -direction ( E x ) has no effect, while the same along the y -direction ( E y ) is found to induce Rashba-type spin splitting at the valence band . The band structure of the CdTe monolayer at E y = 0.4 V/Å is plotted and provided in Figure S3.…”

Electron pairs bound by the spin-orbit interaction in 2D gated Rashba materials with two-band spectrum

“…We base our study on the Bernevig-Hughes-Zhang (BHZ) model [24], which is well established to describe many quasi-2D systems in both topological and trivial phases. However, in this model, Rashba SOI is due to the 𝑠𝑝 3 band hybridization mechanism, which as we found results in a PSOI not strong enough to reliably overcome the Coulomb interaction [16,25]. Nonetheless, the situation is signi cantly improved in the presence of the SOI produced by the electric eld of the gate, which makes it easier to achieve this condition.…”

“…The PSOI is attractive for the electrons in particular spin con gurations tied to their momentum, and competes with the Coulomb repulsion of electrons. Under certain conditions, attainable in materials with the giant Rashba SOI, the PSOI prevails, which leads to the formation of the BEPs [14][15][16]. To date, the BEP formation due to the PSOI was explored within the conduction-band approximation.…”

“…The gate plays several important roles here. The electrons induce the image charges on the gate, the normal electric eld of which contributes to the PSOI [16,26,27].…”