Twisted layers of graphene provide a unique platform for exploring a variety of correlated and topological phases. Among different phases, the cascade phenomena in twisted bilayer graphene, as observed in the spectroscopic properties and electronic compressibility stand out [1]. The cascades extend up to much higher temperatures and a wider range of twist angles than other correlated states, suggesting that the former constitutes the parent state for the latter. These cascades have earlier been described in terms of symmetry broken states. In this talk, I will show that the spectral weight reorganization associated with the formation of local moments and heavy quasiparticles are responsible for the cascade phenomena [2]. Using dynamical mean field theory + Hartree calculations, and without relying on any symmetry broken order, we reproduce the cascade flow of spectral weight and asymmetric jumps of inverse compressibility, observed in experiments.
In the second part, I will shift focus to helical trilayer graphene in a magnetic field [3].
[1] D. Wong et al, Nature 582, 198 (2020), U. Zondiner et al, Nature 582, 203 (2020)
[2] A. Datta, M.J. Calderón, A. Camjayi, and E. Bascones, Nature Communications 14, 5036 (2023)
[3] A. Datta, D. Guerci, M. O. Goerbig, C. Mora, arXiv:2404.15452 (PRB 2024, in press, editors' suggestion)
Zoom Link: https://icts-res-in.zoom.us/j/94037261436?pwd=W8fGiZzqV1X4rP7HWMvRST7q530eTG.1
Meeting ID: 940 3726 1436
Passcode: 202030