Dynamic exciton funneling by local strain control in a monolayer semiconductor

TL;DR

This paper demonstrates a method to dynamically control exciton flux in monolayer semiconductors by applying local strain gradients, enabling reversible and nanoscale tuning of exciton energy for advanced optoelectronic applications.

Contribution

It introduces a novel technique to reversibly and locally tune the bandgap of 2D semiconductors using nanoscale strain gradients, enabling dynamic exciton control.

Findings

Strain gradients can steer exciton flux over micron distances.

Local and reversible bandgap tuning is achieved with a nanoscale tip.

Dynamic modulation of exciton energy is demonstrated via imaging and spectroscopy.

Abstract

The ability to control excitons in semiconductors underlies numerous proposed applications, from excitonic circuits for computing and communications to polariton condensates to energy transport in photovoltaics. 2D semiconductors are particularly promising for room-temperature applications due to their large exciton binding energy. Their enormous stretchability gives rise to a strain-engineerable bandgap that has been used to induce static exciton flux in predetermined structures. However, dynamic control of exciton flux represents an outstanding challenge. Here, we introduce a method to tune the bandgap of suspended 2D semiconductors by applying a local strain gradient with a nanoscale tip. This strain allows us to locally and reversibly shift the exciton energy and to steer the exciton flux over micron-scale distances, as observed by wide-field imaging and time-resolved photoluminescence spectroscopy. We anticipate that the ability to strongly and dynamically modulate the bandgap of a semiconductor at the nanoscale not only marks an important experimental tool but will also open a broad range of new applications from information processing to energy conversion.