Magnetic Dirac Fermions and Chern Insulator Supported on Pristine Silicon Surface

TL;DR

This paper predicts that pristine silicon surfaces can exhibit ferromagnetism and topologically nontrivial states, leading to quantum anomalous Hall effects without external doping, opening new avenues for silicon-based spintronics and quantum computing.

Contribution

It demonstrates, through first-principles calculations, that pristine silicon surfaces can spontaneously develop ferromagnetism and topological properties, a novel route for quantum anomalous Hall effects.

Findings

Pristine Si(111) surface exhibits spin-polarized Dirac surface states.

Spontaneous ferromagnetism and nontrivial topology are predicted on silicon surface.

Quantized anomalous Hall effect with Chern number C=-1 is achieved without doping.

Abstract

Emergence of ferromagnetism in non-magnetic semiconductors is strongly desirable, especially in topological materials thanks to the possibility to achieve quantum anomalous Hall effect. Based on first-principles calculations, we propose that for Si thin film grown on metal substrate, the pristine Si(111)-root3xroot3 surface with a spontaneous weak reconstruction has a strong tendency of ferromagnetism and nontrivial topological properties, characterized by spin polarized Dirac-fermion surface states. In contrast to conventional routes relying on introduction of alien charge carriers or specially patterned substrates, the spontaneous magnetic order and spin-orbit coupling on the pristine silicon surface together gives rise to quantized anomalous Hall effect with a finite Chern number C=-1. This work suggests exciting opportunities in silicon-based spintronics and quantum computing free from alien dopants or proximity effects.