Non-equilibrium band broadening, gap renormalization and band inversion in black phosphorus. (28th January 2021)

• Record Type: Journal Article
• Authors: Hedayat, H; Ceraso, A; Soavi, G; Akhavan, S; Cadore, A; Dallera, C; Cerullo, G; Ferrari, A C; Carpene, E
• Is Part Of: 2D materials. Volume 8:Number 2(2021)
• Publication Date: 2021-01-28
• Subjects: black phosphorus -- time-resolved ARPES -- Stark effect -- surface photovoltage -- bandgap renormalization; Graphene -- Periodicals; Materials science -- Periodicals; Nanostructured materials -- Periodicals; 620.115
• DOI: 10.1088/2053-1583/abd89a
• Languages: English
• ISSNs: 2053-1583

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.