Interaction proximity effect at the interface between a superconductor and a topological insulator quantum well

TL;DR

This paper explores how superconducting proximity effects at interfaces with topological insulator quantum wells can induce novel quantum states, including topological superconductors and fractional topological insulators, with potential applications in quantum computing.

Contribution

It analyzes the induced interactions via field-theoretical methods and proposes device principles for realizing non-Abelian quasiparticles in topological insulator quantum wells.

Findings

Bound-state Cooper pairs can be stabilized inside topological insulator quantum wells.

Spinful triplet pair condensation can lead to new superconducting states.

Proximity-induced interactions may enable fractional topological insulators.

Abstract

A material whose electrons are correlated can affect electron dynamics across the interface with another material. Such a "proximity effect" can have several manifestations, from order parameter leakage to generated effective interactions. The resulting combination of induced electron correlations and their intrinsic dynamics at the surface of the affected material can give rise to qualitatively new quantum states. For example, the leaking of a superconducting order parameter into certain Rashba spin-orbit-coupled materials has been recently identified as a path to creating "topological superconductors" that can host Majorana particles of use in quantum computing. Here we analyze the other aspects of the superconducting proximity effect. The proximity-induced interactions are a promising path to incompressible quantum liquids with non-Abelian fractional quasiparticles in topological insulator quantum wells, which could also find applications in topological quantum computing. We discuss the operational and design principles of a heterostructure device that could realize such states. We apply field-theoretical methods to characterize the properties of induced interactions via the electron-phonon coupling and Cooper pair tunneling across the interface. We argue that bound-state Cooper pairs can be stabilized by the interaction proximity effect inside a topological insulator quantum well at experimentally observable energy scales. The condensation of spinful triplet pairs, enabled by the Rashba spin-orbit coupling and tunable by gate voltage, would lead to novel superconducting states and fractional topological insulators.