Charge state tuning of spin defects in hexagonal boron nitride

TL;DR

This study demonstrates the ability to tune the charge state of boron vacancies in ultrathin hexagonal boron nitride, affecting their optical activity and stability, which is crucial for developing 2D quantum sensors.

Contribution

We show charge state control of boron vacancies in hBN via electric fields, revealing transitions between optically active and inactive states with implications for quantum sensing.

Findings

Charge state transition from singly to doubly negatively charged under bias.

Photoluminescence quenching observed with applied voltage.

Negatively charged boron vacancies are stable against external electric fields.

Abstract

Boron vacancies in hexagonal boron nitride (hBN) are among the most extensively studied optically active spin defects in van der Waals crystals, due to their promising potential to develop two-dimensional (2D) quantum sensors. In this letter, we demonstrate the tunability of the charge state of boron vacancies in ultrathin hBN layers, revealing a transition from the optically active singly negatively charged state to the optically inactive doubly negatively charged state when sandwiched between graphene electrodes. Notably, there is a photoluminescence quenching of a few percent upon the application of a bias voltage between the electrodes. Our findings emphasize the critical importance of considering the charge state of optically active defects in 2D materials, while also showing that the negatively charged boron vacancy remains robust against external perpendicular electric fields. This stability makes it a promising candidate for integration into various van der Waals heterostructures.