posted on 2021-01-28, 22:08authored byLiuyang Sun, Parveen Kumar, Zeyu Liu, Junho Choi, Bin Fang, Sebastian Roesch, Kha Tran, Joshua Casara, Eduardo Priego, Yu-Ming Chang, Galan Moody, Kevin L. Silverman, Virginia O. Lorenz, Michael Scheibner, Tengfei Luo, Xiaoqin Li
A variety
of quantum degrees of freedom, e.g., spins, valleys,
and localized emitters, in atomically thin van der Waals materials
have been proposed for quantum information applications, and they
inevitably couple to phonons. Here, we directly measure the intrinsic
optical phonon decoherence in monolayer and bulk MoS2 by
observing the temporal evolution of the spectral interference of Stokes
photons generated by pairs of laser pulses. We find that a prominent
optical phonon mode E2g exhibits a room-temperature dephasing
time of ∼7 ps in both the monolayer and bulk. This dephasing
time extends to ∼20 ps in the bulk crystal at ∼15 K,
which is longer than previously thought possible. First-principles
calculations suggest that optical phonons decay via two types of three-phonon
processes, in which a pair of acoustic phonons with opposite momentum
are generated.