Quantum spin Hall effect in two-dimensional metals without spin-orbit coupling

TL;DR

This paper proposes an experiment to observe the quantum spin Hall effect in a 2D metal without relying on spin-orbit coupling, using a novel Hamiltonian and magnetic/electric fields, with potential for room-temperature quantum computing.

Contribution

It introduces a new experimental setup and Hamiltonian to observe the quantum spin Hall effect in metals without spin-orbit coupling, and discusses thermal management for room-temperature operation.

Findings

Exact solutions for the quantum Hamiltonians of the proposed experiments.

Designs for controlling Joule heating to enable room-temperature measurements.

Potential development of thermally-managed arrays for quantum computing.

Abstract

The quantum spin Hall effect has been observed in topological insulators using spin-orbit coupling as the probe, but it has not yet been observed in a metal. An experiment is proposed to measure the quantum spin Hall effect of an electron or hole in a two-dimensional (2D) metal by using the previously unexplored but relativistically generated 2D quantum spin Hall Hamiltonian, but without using spin-orbit coupling. A long cylindrical solenoid lies normally through the inner radius of a 2D metallic Corbino disk. The current $I_S$ surrounding the solenoid produces an azimuthal magnetic vector potential but no magnetic field in the disk. In addition, a radial electric field is generated across the disk by imposing either (a) a potential difference $\Delta v$ or (b) a radial charge current ${\bm I}$ across its inner and outer radii. Combined changes in $I_S$ and in either $\Delta v$ or ${\bm I}$ generate spontaneously quantized azimuthal charge and spin currents. The experiment is designed to measure these quantized azimuthal charge and spin currents in the disk consistently. The quantum Hamiltonians for experiments (a) and (b) are both solved exactly. A method to control the Joule heating is presented, which could potentially allow the quantum spin Hall measurements to be made at room temperature. Extensions of this design to an array of thermally-managed solenoids, each surrounded by thermally-managed stacks of 2D metallic Corbino disks, could function as a quantum computer that could potentially operate at room temperature.