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arXiv · 2307.00702

Transport and localization of indirect excitons in a van der Waals heterostructure

L. H. Fowler-Gerace·Zhiwen Zhou·E. A. Szwed·D. J. Choksy·L. V. Butov
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Abstract

Long lifetimes of spatially indirect excitons (IXs), also known as interlayer excitons, allow implementing both quantum exciton systems and long-range exciton transport. Van der Waals heterostructures (HS) composed of atomically thin layers of transition-metal dichalcogenides (TMD) offer the opportunity to explore IXs in moir\'e superlattices. The moir\'e IXs in TMD HS form the materials platform for exploring the Bose-Hubbard physics and superfluid and insulating phases in periodic potentials. IX transport in TMD HS was intensively studied and diffusive IX transport with $1/e$ decay distances $d_{1/e}$ up to $\sim 3$ $\mu$m was realized. In this work, we present in MoSe$_2$/WSe$_2$ HS the IX long-range transport with $d_{1/e}$ exceeding 100 $\mu$m and diverging at the optical excitation resonant to spatially direct excitons. The IX long-range transport vanishes at high temperatures. With increasing IX density, IX localization, then IX long-range transport, and then IX reentrant localization is observed. The results are in qualitative agreement with the Bose-Hubbard theory of bosons in periodic potentials predicting superfluid at $N \sim 1/2$ and insulating at $N \sim 0$ and $N \sim 1$ phases for the number of bosons per site of the periodic potential $N$.

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L. H. Fowler-Gerace, Zhiwen Zhou, E. A. Szwed, D. J. Choksy, L. V. Butov. 2023-07-03. Transport and localization of indirect excitons in a van der Waals heterostructure. https://doi.org/10.1038/s41566-024-01435-w

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