Triggering superconductivity, semiconducting states, and ternary valley structure in graphene via functionalization with Si-N layers

TL;DR

This paper proposes new graphene-based 2D materials passivated with Si-N layers, demonstrating superconductivity, a ternary valley structure, and enhanced optical properties, with potential applications in valleytronics and optoelectronics.

Contribution

It introduces two novel 2D materials, C2SiN and CSiN, with unique electronic, optical, and mechanical properties, expanding the possibilities for 2D material functionalities.

Findings

C2SiN is metallic and superconducting at low temperatures.

CSiN is a stable semiconductor with a controllable ternary valley structure.

Valley polarization affects anisotropic conductivity, detectable via electric measurements.

Abstract

Opening a band gap and realizing static valley control have been long sought after in graphenebased two-dimensional (2D) materials. Motivated by the recent success in synthesizing 2D materials passivated by Si-N layers, here, we propose two new graphene-based materials, 2D C2SiN and CSiN, via first-principles calculations. Monolayer C2SiN is metallic and realizes superconductivity at low temperatures. Monolayer CSiN enjoys excellent stability and mechanical property. It is a semiconductor with a ternary valley structure for electron carriers. Distinct from existing valleytronic platforms, these valleys can be controlled by applied uniaxial strain. The valley polarization of carriers further manifest as a pronounced change in the anisotropic conductivity, which can be detected in simple electric measurement. The strong interaction effects also lead to large exciton binding energy and enhance the optical absorption in the ultraviolet range. Our work opens a new route to achieve superconductivity, ternary valley structure, and semiconductor with enhanced optical absorption in 2D materials.