Hysteretic electronic phase transitions in correlated charge density wave state of 1T-TaS2

Hysteretic electronic phase transitions in correlated charge density wave state of 1T-TaS2

by | May 2, 2023 | 2023, 本组论文

Physical Review B 107, 195401 (2023)

Yanyan Geng, Le Lei, Haoyu Dong, Jianfeng Guo, Shuo Mi, Yan Li, Li Huang, Fei Pang, Rui Xu, Weichang Zhou, Zheng Liu, Wei Ji, and Zhihai Cheng

Abstract:

The layered transition metal dichalcogenide 1T−TaS2 has evoked great interest owing to its particularly rich electronic phase diagram including different charge density wave (CDW) phases. However, few studies have focused on its hysteretic electronic phase transitions based on the in-depth discussion of the delicate interplay among temperature-dependent electronic interactions. Here, we report a sequence of spatial electronic phase transitions in the hysteresis temperature range (160–230 K) of 1T−TaS2 via variable-temperature scanning tunneling microscopy. Several emergent electronic states are investigated at multiscale during the commensurate CDW–triclinic CDW (CCDW-TCDW) phase transitions: a spotty-CDW state above ∼160K, a network-CDW (NCDW) state above ∼180K during the warmup process, a belt-TCDW state below ∼230K, a NCDW state below ∼200K, and finally a mosaic-CDW state below ∼160K during cooldown from the TCDW phase. These emergent electronic states are associated with the delicate temperature-dependent competition and/or cooperation of stacking-dependent interlayer interactions, intralayer electron-electron correlations, and electron-phonon (e−ph) coupling of 1T−TaS2. Our results not only provide insight to understand the hysteretic electronic phase transitions in the correlated CDW state, but also pave a way to realize more exotic quantum states by accurately and effectively tuning various interior interactions in correlated materials.

DOI:10.1103/PhysRevB.107.195401

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Real-space detection and manipulation of two-dimensional quantum well states in few-layer MoS2

Real-space detection and manipulation of two-dimensional quantum well states in few-layer MoS2

by | Feb 8, 2022 | 2022, 本组论文

Phys. Rev. B 105, L081404 (2022)

Yu Wang, Linlu Wu, Zheng Wei, Zijia Liu, Peng Cheng, Yiqi Zhang, Baojie Feng, Guangyu Zhang, Wei Ji, Kehui Wu & Lan Chen

Abstract

Quantum confinement has remarkable effects on the band structures and optoelectronic performance of semiconducting materials. The confinement of electronic states developed along van der Waals (vdW) gaps in transition metal dichalcogenides (TMDs) has unique advantages compared with those of artificial quantum wells. Here, we detected the quantized electronic states of few-layered MoS2 in real space using scanning tunneling microscope/spectroscopy. Combined with density-functional theory calculations, the quantized states were attributed to quantum-well states (QWSs), and the number of the states was strictly determined by the MoS2 layer thickness. We further regulated the QWSs of few-layered MoS2 by tuning the strength of interlayer hybridization through directly adjusting the interlayer distance. More importantly, substitutional defects in few-layered MoS2 were introduced to control the energy eigenvalues of the QWSs. Our work proves the existence of the interlayer electronic hybridization in conventional weakly coupled vdW interfaces, and provides a way to manipulate the electronic states of few-layered TMD through controlling interlayer hybridization. It also suggests potential applications of quantum-well materials in subband transitions, spin splitting, photoexcitation, and electronic devices.