2024/06/20 by Juan José Esteve-Paredes, M. A. García-Blázquez, Esteve-Paredes, J. J. +7 · 3 citations
Engineering · Neuroscience · Physics and Astronomy · #FOS: Physical sciences #Materials Science (cond-mat.mtrl-sci) #Mechanical and Optical Resonators #Mesoscale and Nanoscale Physics (cond-mat.mes-hall) #Photonic and Optical Devices #Photoreceptor and optogenetics research
paper · pdf · doi:10.48550/arxiv.2406.14215
openalex publication_date 2024/06/20 · openalex created_date 2024/06/22 · openalex updated_date 2026/07/28
It is well-known that exciton effects are determinant to understand the optical absorption spectrum of low-dimensional materials. However, the role of excitons in nonlinear optical responses has been much less investigated at an experimental level. Additionally, computational methods to calculate nonlinear conductivities in real materials are still not widespread, particularly taking into account excitonic interactions. We present a methodology to calculate the excitonic second-order optical responses in 2D materials relying on: (i) ab initio tight-binding Hamiltonians obtained by Wannier interpolation and (ii) the Bethe-Salpeter equation with effective electron-hole interactions. Here, in particular, we explore the role of excitons in the shift current of monolayer materials. Focusing on MoS2 and GeS monolayer systems, our results show that 2p-like excitons, which are dark in the linear response regime, yield a contribution to the photocurrent comparable to that of 1s-like excitons. Under radiation with intensity ∼ 104 W/cm2, the excitonic theory predicts in-gap photogalvanic currents of almost ∼ 10 nA in sufficiently clean samples, which is typically one order of magnitude higher than the value predicted by independent-particle theory near the band edge.