posted on 2022-02-07, 15:34authored byVarun Mapara, Arup Barua, Volodymyr Turkowski, M. Tuan Trinh, Christopher Stevens, Hengzhou Liu, Florence A. Nugera, Nalaka Kapuruge, Humberto Rodriguez Gutierrez, Fang Liu, Xiaoyang Zhu, Dmitry Semenov, Stephen A. McGill, Nihar Pradhan, David J. Hilton, Denis Karaiskaj
Magnetic field- and polarization-dependent
measurements on bright
and dark excitons in monolayer WSe2 combined with time-dependent
density functional theory calculations reveal intriguing phenomena.
Magnetic fields up to 25 T parallel to the WSe2 plane lead
to a partial brightening of the energetically lower lying exciton,
leading to an increase of the dephasing time. Using a broadband femtosecond
pulse excitation, the bright and partially allowed excitonic state
can be excited simultaneously, resulting in coherent quantum beating
between these states. The magnetic fields perpendicular to the WSe2 plane energetically shift the bright and dark excitons relative
to each other, resulting in the hybridization of the states at the
K and K′ valleys. Our experimental results are well captured
by time-dependent density functional theory calculations. These observations
show that magnetic fields can be used to control the coherent dephasing
and coupling of the optical excitations in atomically thin semiconductors.