Non-adiabatic suppression of 3D excitonic screening in black phosphorus by mid-infrared pulses

TL;DR

This study demonstrates that mid-infrared pulses can transiently suppress dielectric screening in bulk black phosphorus, revealing new ways to optically manipulate electronic properties of layered semiconductors.

Contribution

It uncovers the non-thermal suppression of dielectric screening in black phosphorus using mid-infrared pulses, highlighting the role of interlayer interactions in electronic property control.

Findings

Transient suppression of dielectric screening observed

Emergence of single-layer exciton resonance

Interlayer interactions influence electronic properties

Abstract

The competition between the electron-hole Coulomb attraction and the three-dimensional dielectric screening dictates the optical properties of layered semiconductors. In low-dimensional materials, the equilibrium dielectric environment can be significantly altered by the ultrafast excitation of photo-carriers, leading to renormalized band gap and exciton binding energies. Recently, black phosphorus emerged as a 2D material with strongly layer-dependent electronic properties. Here, we resolve the coherent response of screening to sub-gap photo-excitation in bulk black phosphorus and find that mid-infrared pulses tuned across the band gap drive a transient non-thermal suppression of the dielectric screening, which is revealed by the emergence of the single-layer exciton resonance. Our work exposes the role of interlayer interactions in determining the electronic properties of 2D materials and discloses the possibility of optically manipulate them, which is of great relevance for the engineering of versatile van der Waals low-dimensional materials.