The Anthony J Leggett Institute for Condensed Matter Theory Seminar - Kyung-Su Kim (UIUC), "Entropy-driven transitions between extended integer and fractional quantum Hall regimes"

Title: Entropy-driven transitions between extended integer and fractional quantum Hall regimes

Abstract: Electronic states in which Wigner-crystal (WC) order coexists with topological order can exhibit quantum (anomalous) Hall (QH/QAH) effects over a finite range of electron densities—i.e., “extended" quantum Hall plateaus in the absence of disorder. Such extended quantum Hall states can compete with other QH states at the same density, allowing a first-order thermal transition between them. In this talk, I will analyze several settings in which the entropy associated with Goldstone modes (e.g., magnons or phonons) or soft gapped modes (e.g., magnetoroton) drives such a transition. Applied to moiré rhombohedral graphene, we argue that a sufficiently soft FQAH magnetoroton provides a plausible bulk mechanism for the observed thermal evolution from the extended integer quantum anomalous Hall (EIQAH) regime to the fractional quantum anomalous Hall (FQAH) regime.

Zoom Link: https://illinois.zoom.us/my/icmt.seminar?pwd=ZU1KbnBLeXZLUmJKc0oyU205cDNDdz09

Meeting ID: 791 382 8328

Password: 106237