Dirac spin gapless semiconductors: Ideal platforms for massless and dissipationless spintronics and new (quantum) anomalous spin Hall effects

TL;DR

This paper introduces spin-gapless semiconductors with linear energy dispersion as ideal, dissipationless platforms for advanced spintronics and proposes four novel (quantum) anomalous spin Hall effects involving spin accumulation without Hall voltage.

Contribution

It identifies spin-gapless semiconductors as unique materials for massless, dissipationless spintronics and proposes four new types of spin Hall effects with potential experimental realization.

Findings

Spin-gapless semiconductors enable massless, dissipationless spin transport.

Four new (quantum) anomalous spin Hall effects are theoretically proposed.

Candidate materials include ferromagnetic monolayers of simple oxides with specific lattice structures.

Abstract

It is proposed that the new generation of spintronics should be ideally massless and dissipationless for the realization of ultra-fast and ultra-low-power spintronic devices. We demonstrate that the spin-gapless materials with linear energy dispersion are unique materials that can realize these massless and dissipationless states. Furthermore, we propose four new types of spin Hall effects which consist of spin accumulation of equal numbers of electrons and holes having the same or opposite spin polarization at the sample edge in Hall effect measurements, but with vanishing Hall voltage. These new Hall effects can be classified as (quantum) anomalous spin Hall effects. The physics for massless and dissipationless spintronics and the new spin Hall effects are presented for spin-gapless semiconductors with either linear or parabolic dispersion. New possible candidates for Dirac-type or parabolic type spin-gapless semiconductors are demonstrated in ferromagnetic monolayers of simple oxides with either honeycomb or square lattices.