Non-equilibrium band broadening, gap renormalization and band inversion in black phosphorus


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Authors
Hedayat, H 
Ceraso, A 
Soavi, G 
Akhavan, S 
Cadore, A 
Abstract

Abstract: Black phosphorous (BP) is a layered semiconductor with high carrier mobility, anisotropic optical response and wide bandgap tunability. In view of its application in optoelectronic devices, understanding transient photo-induced effects is crucial. Here, we investigate by time- and angle-resolved photoemission spectroscopy BP in its pristine state and in the presence of Stark splitting, chemically induced by Cs ad-sorption. We show that photo-injected carriers trigger bandgap renormalization, and a concurrent valence band flattening caused by Pauli blocking. In biased samples, photo-excitation leads to a long-lived (ns) surface photovoltage of few hundreds mV that counterbalances the Cs-induced surface band bending. This allows us to disentangle bulk from surface electronic states, and to clarify the mechanism underlying the band inversion observed in bulk samples.

Description

Funder: ERC Grants Hetero2D


Funder: GSYNCOR


Funder: EU Graphene Flagship

Keywords
Paper, black phosphorus, time-resolved ARPES, Stark effect, surface photovoltage, bandgap renormalization
Journal Title
2D Materials
Conference Name
Journal ISSN
2053-1583
Volume Title
8
Publisher
IOP Publishing
Sponsorship
PRIN (2017BZPKSZ)
EPSRC Grants (EP/K01711X/1)
EPSRC Grants (EP/K017144/1, EP/L016087/1, EP/N010345/1)