# Electrical Control of Intersubband Transitions in Few-Layer WSe2 Multivalley Quantum Wells Probed by Electronic Raman Scattering

## TL;DR

Researchers demonstrated electrical control of light-matter interactions in few-layer WSe2 quantum wells, enabling tunable optoelectronic applications.

## Contribution

First demonstration of electrically tunable intersubband transitions in van der Waals quantum wells using Raman scattering.

## Key findings

- Intersubband transitions in WSe2 can be tuned by over 100 meV using an electric field.
- Tunability is consistent across 3 to 7 layers of WSe2, with measured dipole moments and polarizabilities.
- Artificially stacked WSe2 layers show twist-angle-dependent manipulation of transitions.

## Abstract

Semiconducting quantum wells have enabled revolutionary
applications
in diode lasers, IR photodetectors, and optical modulators. Recently,
van der Waals (vdW) quantum wells have emerged as a promising frontier,
offering inherently atomically sharp interfaces and facile integration
into device structures without the constraints of lattice matching.
Tunability of intersubband transitions is essential for applications
of quantum wells but remains unexplored in vdW structures. Here, we
report valley-selective, electric-field-activated electronic Raman
scattering from intersubband transitions in natural WSe2 multilayers and demonstrate electrical tunability by over 100 meV.
We validate the generality of such tunability in 3 to 7 layers of
WSe2 and quantify the effective dipole moments and polarizabilities
that determine the quantum-confined Stark effect. These intersubband
transitions are also found in artificially stacked multilayers, where
they can be manipulated by twist angle. Our work lays foundations
for exploiting vdW quantum wells in next-generation optoelectronic
applications, including tunable photodiodes and atomically compact
IR spectrometers.