Thermo-induced motional Stark effect on magnetoexciton energy spectra in monolayer transition-metal dichalcogenides

Duy-Nhat Ly, Dai-Nam Le, Ngoc-Hung Phan, Van-Hoang Le

Published 2022-09-27Version 1

Although energy spectra of an exciton in monolayer transition-metal dichalcogenides (TMDCs) with a magnetic field were measured at different temperatures, the theoretical calculations have been performed, neglecting the temperature effect till now. In the present work, we suggest a new mechanism that allows the thermal motion of the exciton's center of mass to affect the exciton energies. We first recall that the center of mass (c.m.) of a two-body system in a magnetic field is no longer free and then use a non-trivial scheme for its separation. The obtained equation for the relative motion contains a specific term (related to the motional Stark effect) proportional to the c.m. pseudomomentum, whose average, in turn, is related to the temperature of the exciton gas. By solving the Schrodinger equation without omitting the motional Stark potential, we show that the thermo-induced effect on the exciton energies is significant enough for experimental detection. The symmetry breaking of the system due to the additional term and the thermo-induced effect on the exciton radius and diamagnetic coefficient are also discussed by examining the wave functions. Some consequences are studied, especially the enhancement of exciton lifetime and the appearance of new peaks in the absorption spectra besides those of the s-states. This study could fill the gap between the present theoretical calculations and experimental measurements on energy spectra of magnetoexciton in monolayer TMDCs at finite temperatures.