Finite temperature study of generalized Wigner crystals

by Dr Aman Kumar (NHMFL, Tallahassee)

Friday 29 Aug 2025, 16:00 → 18:00 Asia/Kolkata

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Generalized Wigner crystals (GWC) on triangular moir´e superlattices, formed from stacking two layers of transition metal chalcogenides, have been observed at multiple fractional fillings [Nature 587, 214 - 218 (2020), Nat. Phys. 17, 715 - 719 (2021), Nature 597, 650 - 654 (2021)]. Motivated by these experiments, tied with the need for accurate microscopic descriptions of these materials, we explore the origins of GWC at n = 1/3, 2/3, 1/2 and 1/4 filling. We demonstrate the general limitations of theoretical descriptions relying on finite-range, versus long-range interactions, however, we clarify why some properties are captured by an effective nearest-neighbor model. We study both classical and quantum effects at zero and finite temperatures, discussing the role of charge frustration, identifying a “pinball” phase, a partially quantum melted GWC, with no classical analog.

 

We further investigate the temperature versus quantum parameter (t/V) phase diagram across different fillings. At n = 1/2, we find that Tc increases monotonically with t/V, in contrast to the behaviour expected from a critical fan phase diagram. Our work addresses several experimental observations and makes predictions for how many of the theoretical findings can be potentially realized in future experiments.