Electronic and optical properties of two-dimensional InSe from a DFT-parameterized tight-binding model

TL;DR

This paper develops a tight-binding and k·p model for monolayer and few-layer InSe, revealing how optical properties and band dispersions depend on the number of layers, with results aligning with recent experimental findings.

Contribution

The paper introduces a DFT-parameterized tight-binding model for InSe, providing detailed insights into its electronic and optical properties across different layer counts.

Findings

Optical transition energies vary strongly with layer number.

Conduction electrons are relatively light with effective masses 0.14-0.18 m_e.

Valence band holes exhibit flat, slightly inverted dispersion near Γ.

Abstract

We present a tight-binding (TB) model and $\mathbf{k\cdot p}$ theory for electrons in monolayer and few-layer InSe. The model is constructed from a basis of all $s$ and $p$ valence orbitals on both indium and selenium atoms, with tight-binding parameters obtained from fitting to independently computed density functional theory (DFT) band structures for mono- and bilayer InSe. For the valence and conduction band edges of few-layer InSe, which appear to be in the vicinity of the $\Gamma$ point, we calculate the absorption coefficient for the principal optical transitions as a function of the number of layers, $N$. We find a strong dependence on $N$ of the principal optical transition energies, selection rules, and optical oscillation strengths, in agreement with recent observations \cite{Bandurin2016}. Also, we find that the conduction band electrons are relatively light ($m \propto 0.14-0.18 m_e$), in contrast to an almost flat, and slightly inverted, dispersion of valence band holes near the $\Gamma$-point, which is found for up to $N \propto 6$.