Abstract
MoSe2–WSe2 heterostructures host strongly bound interlayer excitons (IXs), which exhibit bright photoluminescence (PL) when the twist angle is near 0° or 60°. Over the past several years, there have been numerous reports on the optical response of these heterostructures but no unifying model to understand the dynamics of IXs and their temperature dependence. Here we perform a comprehensive study of the temperature, excitation power, and time-dependent PL of IXs. We observe a significant decrease in PL intensity above a transition temperature that we attribute to a transition from localized to delocalized IXs. Astoundingly, we find a simple inverse relationship between the IX PL energy and the transition temperature, which exhibits opposite power-dependent behaviors for near 0° and 60° samples. We conclude that this temperature dependence is a result of IX–IX exchange interactions, whose effect is suppressed by the moiré potential trapping IXs at low temperature.
Highlights
The interlayer excitons (IXs) of MoSe2–WSe2 heterostructures comprise an electron in the MoSe2 layer bound to a hole in the WSe2 layer
Contrasting R- and H-type heterostructures In this article, we investigate the physics of IXs in five different hBN-encapsulated MoSe2–WSe2 heterostructures by performing temperature, excitation power, and time-resolved PL measurements
We note that R-type samples show a single dominant singlet IX peak at low temperature and power, which broadens with increasing temperature and power to higher energy (Fig. 1b)
Summary
These IXs have been the subject of intense research in recent years[1,2,3,4,5,6,7,8,9,10,11,12,13,14,15]; a fundamental observation of the IX, the strongly temperature-dependent photoluminescence (PL) intensity, has been largely unexplained. The recent reports on trapping IXs at moiré potentials motivate a new exploration of IX dynamics in the context of the moiré-trapped IXs6,7,10,12,20,21
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