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Berlin 2024 – wissenschaftliches Programm

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HL: Fachverband Halbleiterphysik

HL 24: Graphene and 2D Materials (joint session TT/HL)

HL 24.2: Vortrag

Mittwoch, 20. März 2024, 09:45–10:00, H 3007

Berry Phase Effects in the Transverse Conductivity of Fermi Surfaces and its Detection With Spin Qubits and NMR — •Mark Morgenthaler and Inti Sodemann — Universität Leipzig, Germany

The transverse conductivity of clean Fermi liquids at low frequencies displays a remarkably universal behaviour at long wavelengths: It is determined only by the geometrical radius of curvature of the Fermi surface, and does not depend on details such as the quasi-particle mass or their interactions. Here, we demonstrate that the Berry phase at the Fermi surface does not alter such long-wavelength universality by directly computing the transverse conductivity of two- and three-dimensional electronic systems with Dirac dispersions, such as those appearing in 2D graphene or in 3D Dirac semi-metals and in the bulk of 3D topological insulators. Interestingly however, such universality ceases to hold at wave-vectors comparable to the Fermi radius, and Dirac fermions display a distinct transverse conductivity from a featureless parabolic Fermion. We demonstrate that this difference originates entirely from the orbital magnetic moment of the quasi-particles induced by their Berry phases. We discuss how these effects can be probed by measuring the T1 relaxation time of spin qubits (such as NV centers) near 2D samples and for the nuclear spins measured in NMR for 3D samples.

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