Berlin 2024 – wissenschaftliches Programm
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TT: Fachverband Tiefe Temperaturen
TT 88: 2D Materials and Heterostuctures: (Twisted) Bilayers (joint session HL/TT)
TT 88.7: Hauptvortrag
Freitag, 22. März 2024, 11:15–11:45, EW 201
Correlated phases in the vicinity of tunable van Hove singularities in Bernal bilayer graphene — •Anna Seiler1, Nils Jacobsen1, Martin Statz1, Fabian Geisenhof2, Felix Winterer2, Isabell Weimer1, Tianyi Xu3, Zhiyu Dong4, Leonid Levitov4, Fan Zhang3, and Thomas Weitz1 — 1University of Göttingen — 2Ludwig-Maximilians-Universität München — 3University of Texas at Dallas — 4Massachusetts Institute of Technology
The bandstructure of naturally occurring Bernal bilayer graphene exhibits four linearly-dispersed Dirac cones but changes drastically when large electric displacement fields are applied across the two layers. Here, tunable van Hove singularities lead to the emergence of complex correlated states. We observe experimental signatures consistent with various interaction-driven phases, including the fractional metals of Stoner type [1, 2]. More prominently, we find competing nontrivial insulating and metallic phases at hole doping that exhibit intriguing temperature dependences and nonlinear I-V characteristics at zero magnetic fields [1]. In addition, we report a novel interaction-driven behaviour in the Stoner phases in the electron-doped regime electricfield gapped Bernal bilayer graphene [2]. Specifically, we reveal that the spin- and valley-polarized phases exhibit an insulator-like temperature dependence of the conductance that challenges the conventional picture of metallic Stoner magnetism.
[1] A. M. Seiler et al., Nature 608, 298-302 (2022)
[2] A. M. Seiler et al., arXiv:2308.00827 (2023)
Keywords: Bernal bilayer graphene; Quantum transport; Correlated phases; Correlated insulators; Stoner ferromagnetism