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

TL;DR

This paper demonstrates the emergence of bound electron pairs in 2D gated Rashba materials due to spin-orbit interactions and unique band structure effects, with binding energies tunable by gate voltage.

Contribution

It introduces a mechanism for bound electron pairs in 2D Rashba systems arising from Coulomb-induced spin-orbit interaction and negative effective mass, modeled with the Bernevig-Hughes-Zhang framework.

Findings

Bound electron pairs appear in 2D Rashba materials due to Coulomb and band structure effects.

Binding energy varies significantly with gate voltage.

Bound pairs possess a magnetic moment influenced by orbital motion.

Abstract

We show that the bound electron pairs (BEPs) emerge in two-dimensional gated Rashba materials owing to the interplay of the pair spin-orbit interaction, produced by the Coulomb fields of interacting electrons, and the peculiarities of the band structure giving rise to a negative reduced mass of the interacting electrons. Our consideration is based on the four-band Bernevig-Hughes-Zhang model with the Rashba spin-orbit interaction created by the charges on the gate. The binding energy of the BEP varies with the gate voltage in a wide range across the entire width of the two-particle energy gap. Although the spin-orbit interaction destroys the spin quantization, the BEPs have a magnetic moment, which is created mainly by the orbital motion of the electrons and tuned by the gate voltage.