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MP: Fachverband Theoretische und Mathematische Grundlagen der Physik

MP 1: Many-body Theory I

MP 1.8: Talk

Monday, March 18, 2024, 12:20–12:40, HL 001

Landau quantization near generalized van Hove singularities: magnetic breakdown and orbit networks — •Vladimir A. Zakharov¹, Ahmet Mert Bozkurt^2,3, Anton R. Akhmerov², and Dmytro O. Oriekhov² — ¹Instituut-Lorentz, Universiteit Leiden, P.O. Box 9506, 2300 RA Leiden, The Netherlands — ²Kavli Institute of Nanoscience, Delft University of Technology, Delft 2600 GA, The Netherlands — ³QuTech, Delft University of Technology, Delft 2600 GA, The Netherlands

We develop a theory of magnetic breakdown (MB) near high-order saddle points in the dispersions of two-dimensional materials, where two or more semiclassical cyclotron orbits approach each other. MB occurs due to quantum tunneling between several trajectories, which leads to non-trivial scattering amplitudes and phases. We show that for any saddle point this problem can be solved by mapping it to a scattering problem in a 1D tight-binding chain. Moreover, the occurrence of magnetic breakdown on the edges of the Brillouin zone facilitates the delocalization of the bulk Landau level states and the formation of 2D orbit networks. These extended network states compose dispersive mini-bands with finite energy broadening. This effect can be observed in transport experiments as a strong enhancement of the longitudinal bulk conductance in a quantum Hall bar. In addition, it may be probed in STM experiments by visualizing bulk current patterns.

Keywords: generalized van Hove singularities; Landau quantization; open orbit networks; magnetic breakdown