Evidence of Rotational Fröhlich Coupling in Polaronic Trions
Maxim Trushin, Soumya Sarkar, S. Mathew, Sreetosh Goswami, Prasana K. Sahoo, Yan Wang, Jieun Yang, Weiwei Li, Judith L. MacManus‐Driscoll, Manish Chhowalla, Shaffique Adam, T. Venkatesan
Abstract
Electrons commonly couple through Fröhlich interactions with longitudinal optical phonons to form polarons. However, trions possess a finite angular momentum and should therefore couple instead to rotational optical phonons. This creates a polaronic trion whose binding energy is determined by the crystallographic orientation of the lattice. Here, we demonstrate theoretically within the Fröhlich approach and experimentally by photoluminescence emission that the bare trion binding energy (20 meV) is significantly enhanced by the phonons at the interface between the two-dimensional semiconductor MoS_{2} and the bulk transition metal oxide SrTiO_{3}. The low-temperature binding energy changes from 60 meV in [001]-oriented substrates to 90 meV for [111] orientation, as a result of the counterintuitive interplay between the rotational axis of the MoS_{2} trion and that of the SrTiO_{3} phonon mode.