Optimizing optical properties of bilayer PtSe$_2$: the role of twist angle and hydrostatic pressure

TL;DR

This study uses first-principles calculations to show how twisting and pressure can significantly alter the electronic and optical properties of bilayer PtSe₂, enabling new optoelectronic applications.

Contribution

It reveals the effects of twist angle and hydrostatic pressure on the electronic structure and optical activity of bilayer PtSe₂, demonstrating tunability for device engineering.

Findings

At 13.17° twist angle, bilayer PtSe₂ becomes a direct-gap semiconductor.

Hydrostatic pressure enhances near-infrared optical activity.

Twisting and pressure significantly modify electronic and optical properties.

Abstract

Two-dimensional van der Waals materials offer exceptional tunability in their electronic properties. In this paper, we explore how twisting and hydrostatic pressure can be leveraged to engineer the electronic and optical characteristics of bilayer PtSe$_2$. Using state-of-the-art first-principles density functional methods, we calculate the electronic band structure and the imaginary part of the dielectric function across multiple twist angles and pressure values. We find, that at the twist angle $\theta=13.17^\circ$, bilayer PtSe$_2$, which is intrinsically an indirect semiconductor, transforms into a direct-gap semiconductor. Moreover, we demonstrate that hydrostatic out-of-plane pressure boosts near-infrared optical activity, further expanding the functional potential of PtSe$_2$ bilayers. The demonstrated high tunability of electronic and optical properties by twisting and pressure opens new application directions of PtSe$_2$ in optoelectronics.