Spectroscopy study of electronic correlations in transition metal dichalcogenides moiré superlattices

• Applicant: Dr. Wenhao Zheng
• Subject Area: Experimental Condensed Matter Physics ; Physical Chemistry of Solids and Surfaces, Material Characterisation
• Term: since 2023
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 531466922

Moiré superlattices in transition metal dichalcogenide (TMD) have emerged as a platform for exploring the physics of strong electronic correlations and non-trivial band topology. Given the rapidly increasing interest in TMD moiré superlattices for studying many-body physics and phenomena, such as Mott transitions, Wigner crystallization, and superconductivity, it is crucial to acquire a comprehensive understanding of the underlying strong electronic correlations. Most experiments on 2D moiré superlattices have mainly focused on electron transport measurements, which typically require additional encapsulated layers or gating structures. However, these experimental conditions make it challenging to study the superlattices using common spectroscopic techniques like scanning tunnelling spectroscopy. Developing advanced spectroscopic techniques that can access buried heterostructures is critical for gaining a fundamental understanding of correlated physics in 2D moiré superlattices. In this proposal, our overarching goal is to achieve a comprehensive understanding of electron correlations in TMD moiré superlattices, by utilizing a combination of dual-gate field-effect devices and various spectroscopy tools. We aim to focus on three selected, open, and timely scientific questions: (i) we will investigate the bandwidth of flat band and Mott transition in MoTe2/WSe2 moiré superlattices using Fourier transform infrared (FTIR)-photocurrent spectroscopy; (ii) we will precisely control the charge density in MoTe2/WSe2 moiré superlattices and study the optical transition of generalized Wigner crystals by FTIR-photocurrent spectroscopy; (iii) we aim to provide spectroscopic evidence of the formation of Wigner crystals in WSe2 monolayer semiconductors by developing an on-chip THz spectroscopy based on gated monolayer devices. Overall, the systematic spectroscopy studies in TMD Moiré superlattices provide insights into Hubbard physics of strongly correlated electron systems, which could be relevant to the potential technological innovations.

• DFG Programme: WBP Fellowship
• International Connection: USA
• Host: Professor Dr. Long Ju