Microsecond dark-exciton valley polarization
memory in two-dimensional heterostructures
, Weigao Xu
, Abdullah Rasmita
, Zumeng Huang
& Wei-bo Gao
Transition metal dichalcogenides have valley degree of freedom, which features optical
selection rule and spin-valley locking, making them promising for valleytronics devices and
quantum computation. For either application, a long valley polarization lifetime is crucial.
Previous results showed that it is around picosecond in monolayer excitons, nanosecond for
local excitons and tens of nanosecond for interlayer excitons. Here we show that the dark
excitons in two-dimensional heterostructures provide a microsecond valley polarization
memory thanks to the magnetic ﬁeld induced suppression of valley mixing. The lifetime of the
dark excitons shows magnetic ﬁeld and temperature dependence. The long lifetime and valley
polarization lifetime of the dark exciton in two-dimensional heterostructures make them
promising for long-distance exciton transport and macroscopic quantum state generations.
Division of Physics and Applied Physics, School of Physical and Mathematical Sciences, Nanyang Technological University, Singapore 637371 Singapore.
NOVITAS, Nanoelectronics Center of Excellence, School of Electrical and Electronic Engineering, Nanyang Technological University, Singapore 639798,
MajuLab, CNRS-Université de Nice-NUS-NTU International Joint Research Unit UMI 3654, Singapore 637371, Singapore.
Institute and Centre for Disruptive Photonic Technologies, Nanyang Technological University, 637371 Singapore Singapore. Correspondence and requests for
materials should be addressed to Q.X. (email: firstname.lastname@example.org) or to W.-b.G. (email: email@example.com)