A gate-tunable ambipolar quantum phase transition in a topological excitonic insulator

• Main Authors: Que, Yande, Chan, Yang-Hao, Jia, Junxiang, Das, Anirban, Tong, Zheng Jue, Chang, Yu-Tzu, Cui, Zhenhao, Kumar, Amit, Singh, Gagandeep, Mukherjee, Shantanu, Lin, Hsin, Weber, Bent
• Other Authors: School of Physical and Mathematical Sciences
• Format: Article
• Language: English
• Published: 2024
• Subjects: Physics; Charge density wave; Quantum phase transition
• Online Access: https://hdl.handle.net/10356/175467; http://arxiv.org/abs/2309.16260v1
• Institution: Nanyang Technological University

Coulomb interactions among electrons and holes in 2D semimetals with overlapping valence and conduction bands can give rise to a correlated insulating ground state via exciton formation and condensation. One candidate material in which such excitonic state uniquely combines with non-trivial band topology are atomic monolayers of tungsten ditelluride (WTe2 ), in which a 2D topological excitonic insulator (2D TEI) forms. However, the detailed mechanism of the 2D bulk gap formation in WTe2 , in particular with regard to the role of Coulomb interactions, has remained a subject of ongoing debate. Here, it shows that WTe2 is susceptible to a gate-tunable quantum phase transition, evident from an abrupt collapse of its 2D bulk energy gap upon ambipolar field-effect doping. Such gate tunability of a 2D TEI, into either n- and p-type semimetals, promises novel handles of control over non-trivial 2D superconductivity with excitonic pairing.