Electric field effect on superconductivity in atomically thin flakes of ${\text{NbSe}}_{2}$

Electric field effect on superconductivity in atomically thin flakes of ${NbSe}_{2}$

Neal E. Staley, Jian Wu, Peter Eklund, Ying Liu, Linjun Li, and Zhuan Xu

Phys. Rev. B 80, 184505 – Published 12 November 2009

Abstract

We studied the electric field effect on superconductivity in atomically thin flakes of ${NbSe}_{2}$ prepared by mechanical exfoliation. We found that these ${NbSe}_{2}$ flakes are superconducting down to a thickness of a single unit cell consisting of two molecular layers of ${NbSe}_{2}$ with an onset superconducting transition temperature $(T_{c})$ up to 2.5 K. We demonstrated that the $T_{c}$ of the thinnest flakes can be modulated by an applied gate voltage with a $T_{c}$ shift as large as 200 mK, which is larger than expected from a simple consideration based on Bardeen-Cooper-Schrieffer theory. We discuss the possible reasons for the observed enhanced electric field modulation of $T_{c}$ .