Zero-point electron-phonon renormalization reshapes shift current in monolayer MoS2, calculation shows

An arXiv · preprint, not yet peer reviewed, reports first-principles calculations of the shift current in monolayer MoS2. The shift current drives the bulk photovoltaic effect, which holds promise for near-instantaneous, low-dissipation photodetection and energy conversion arxiv.orgarXiv · препринтarxiv.orgOpen source ↗. The authors identify a contribution that had not been addressed before and call it the band-renormalized shift current (BRSC) arxiv.orgarXiv · препринтarxiv.orgOpen source ↗.

Current understanding relies mainly on a single-particle picture, in which the shift current is determined purely by band dispersion. Effects from directly excited quasiparticles such as excitons, magnons and phonons have already been explored. The renormalization of electronic states by quantum virtual-phonon coupling, which is inherent in essentially all solids, remained unaddressed arxiv.orgarXiv · препринтarxiv.orgOpen source ↗.

According to the calculations, zero-point renormalization alone substantially reshapes the shift-current spectrum. This happens without any polarization-carrying photoexcited phonons and with barely any change in band dispersion. New low-energy peaks arise from phonon-assisted optical transitions between states with different momenta, and higher-energy features shift to lower energy (redshift) arxiv.orgarXiv · препринтarxiv.orgOpen source ↗.

A strain of just 1.0% sharply tunes the BRSC, while raising the temperature enhances it, the authors report. They conclude that electron-phonon coupling is an indispensable ingredient in the description of nonlinear photocurrent, and point to combined strain and temperature control as a route to engineering optoelectronic responses arxiv.orgarXiv · препринтarxiv.orgOpen source ↗.