Expansion of a Valley-Polarized Exciton Cloud in a 2D Heterostructure

TL;DR

This study demonstrates the creation and expansion of a valley-polarized exciton cloud in a 2D heterostructure, revealing long-lived polarization and exchange interactions, advancing valleytronics and quantum optoelectronics.

Contribution

We experimentally realize valley-specific interlayer excitons with long polarization lifetimes in monolayer heterostructures, and observe their spatial expansion and pattern evolution.

Findings

Valley polarization lifetime of 40 nanoseconds.

Visualization of exciton cloud expansion over several microns.

Formation of a polarization ring indicating exchange interactions.

Abstract

Heterostructures comprising different monolayer semiconductors provide a new system for fundamental science and device technologies, such as in the emerging field of valleytronics. Here, we realize valley-specific interlayer excitons in monolayer WSe2-MoSe2 vertical heterostructures. We create interlayer exciton spin-valley polarization by circularly polarized optical pumping and determine a valley lifetime of 40 nanoseconds. This long-lived polarization enables the visualization of the expansion of a valley-polarized exciton cloud over several microns. The spatial pattern of the polarization evolves into a ring with increasing exciton density, a manifestation of valley exciton exchange interactions. Our work lays a foundation for quantum optoelectronics and valleytronics based on interlayer excitons in van der Waals heterostructures.