From Anomalous to Normal: Temperature Dependence of the Band Gap in Two-Dimensional Black Phosphorus

TL;DR

This study investigates how the temperature dependence of the band gap in black phosphorus changes from anomalous in bulk to normal in monolayers, highlighting the role of interlayer coupling.

Contribution

It reveals the crossover from anomalous to normal temperature behavior of the band gap in black phosphorus as the layer number decreases.

Findings

Temperature effect on BP band gap evolves with layer number.

Monolayer BP exhibits normal temperature dependence.

Interlayer coupling influences temperature-dependent optical properties.

Abstract

The temperature dependence of the band gap is crucial to a semiconductor. Bulk black phosphorus (BP) is known to exhibit an anomalous behavior. Through optical spectroscopy, here we show that the temperature effect on BP band gap gradually evolves with decreasing layer number, eventually turns into a normal one in the monolayer limit, rendering a crossover from the anomalous to the normal. Meanwhile, the temperature-induced shift in optical resonance also differs with different transition indices for the same thickness sample. A comprehensive analysis reveals that the temperature-tunable interlayer coupling is responsible for the observed diverse scenario. Our study provides a key to the apprehension of the anomalous temperature behavior in certain layered semiconductors.