在低维条件下，量子效应得以突显，材料往往展现出新颖的物理性质。近年来，维度已发展成为研究与调控材料性质的重要自由度。本课题组致力于探索低维量子材料的光学、电学特性，尤其关注相变物理与集体激发的探测和调控；曾在二维超导、电荷密度波等凝聚态物理的前沿方向发现了一系列新效应。

代表性论文：

（†：共同一作，*：通讯作者）

1. Y. Du†, G. Liu†, W. Ruan†, Z. Fang, K. Watanabe, T. Taniguchi, R. Liu, J.-X. Li, X. Xi*, “Unveiling resilient superconducting fluctuations in atomically thin NbSe₂ through Higgs mode spectroscopy”, Physical Review Letters 134, 066002 (2025). (Editors' Suggestion)

Featured in Physics: Strong Hints of a Bose Metal

Highlighted in the Journal Club for Condensed Matter Physics: Bose Metal in Atomically Thin NbSe2?

2. Y. Li†*, L. Xu†, G. Liu†, Y. Fang†, H. Zheng, S. Dai, E. Li, G. Zhu, S. Zhang, S. Liang, L. Yang, F. Huang, X. Xi*, Z. Liu*, N. Xu*, and Y. Chen, “Evidence of strong and mode-selective electron-phonon coupling in the topological superconductor candidate 2M-WS₂”, Nature Communications 15, 6235 (2024).

3. G. Liu†, T. Qiu†, K. He†, Y. Liu, D. Lin, Z. Ma, Z. Huang, W. Tang, J. Xu, K. Watanabe, T. Taniguchi, L. Gao, J. Wen, J.-M. Liu, B. Yan*, and X. Xi*, “Electrical switching of ferro-rotational order in nanometre-thick 1T-TaS₂ crystals”, Nature Nanotechnology 18, 854 (2023).

      News & Views: Voltage enables ferro-rotational domain switching

4.  H. F. Yang†, K. Y. He†, J. Koo†, S. W. Shen, S. H. Zhang, G. Liu, Y. Z. Liu, C. Chen, A. J. Liang, K. Huang, M. X. Wang, J. J. Gao, X. Luo, L. X. Yang, J. P. Liu, Y. P. Sun, S. C. Yan, B. H. Yan*, Y. L. Chen*, X. Xi*, and Z. K. Liu*, “Visualization of chiral electronic structure and anomalous optical response in a material with chiral charge density waves”, Physical Review Letters 129, 156401 (2022). 

5.  G. Liu, X. Ma, K. He, Q. Li, H. Tan, Y. Liu, J. Xu, W. Tang, K. Watanabe, T. Taniguchi, L. Gao, Y. Dai, H.-H. Wen, B. Yan* & X. Xi*, “Observation of anomalous amplitude modes in the kagome metal CsV₃Sb₅”, Nature Communications 13, 3461 (2022). 

6. D. Lin, S. Li, J. Wen, H. Berger, L. Forró, H. Zhou, S. Jia, T. Taniguchi, K. Watanabe, X. Xi*, and M. S. Bahramy*, “Patterns and driving forces of dimensionality-dependent charge density waves in 2H-type transition metal dichalcogenides”, Nature Communications 11, 2406 (2020). 

7. X. Xi†, Z. Wang†, K. T. Law, H. Berger, L. Forró, J. Shan*, and K. F. Mak*, “Ising paring in superconducting NbSe₂ atomic layers”, Nature Physics 12, 139 (2016).  

      News & Views: The Ising on the monolayer

8. X. Xi, H. Berger, L. Forró, J. Shan*, and K. F. Mak*, “Gate tuning of electronic phase transitions in two-dimensional NbSe₂”, Physical Review Letters 117, 106801 (2016). (Editors' Suggestion)

9. X. Xi, L. Zhao, Z. Wang, H. Berger, L. Forró, J. Shan*, and K. F. Mak*, “Strongly enhanced charge density wave order in monolayer NbSe2”, Nature Nanotechnology 10, 765 (2015). 

      News & Views: Charge density waves go nano

10. X. Xi, X.-G. He, F. Guan, Z. Liu, R. D. Zhong, J. A. Schneeloch, T. S. Liu, G. D. Gu, X. Du, Z. Chen, X. G. Hong, W. Ku, and G. L. Carr, “Bulk signatures of pressure-induced band inversion and topological phase transitions in Pb_1−xSn_xSe”, Physical Review Letters 113, 096401 (2014).

11. X. Xi, C. Ma, Z. Liu, Z. Chen, W. Ku, H. Berger, C. Martin, D. B. Tanner, and G. L. Carr, “Signatures of a pressure-induced topological quantum phase transition in BiTeI”, Physical Review Letters 111, 155701 (2013).

12. X. Xi, J. Hwang, C. Martin, D. B. Tanner, and G. L. Carr, “Far-infrared conductivity measurements of pair breaking in superconducting Nb_0.5Ti_0.5N thin films induced by an external magnetic field”, Physical Review Letters 105, 257006 (2010).