Regensburg 2025 – wissenschaftliches Programm

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HL: Fachverband Halbleiterphysik

HL 18: Focus Session: Nanoscale Light-matter Interaction I

HL 18.2: Hauptvortrag

Dienstag, 18. März 2025, 10:00–10:30, H17

Landau level Nanoscopy of charge and heat transport in low-dimensional heterostructures — •Mengkun Liu — Stony Brook University

In contemporary condensed matter physics and photonics, four key length scales play an essential role in shaping the behavior of quantum materials: (1) the polaritonic wavelength, which governs light confinement and light-matter interactions; 2) the magnetic lengths, determined by the magnetic field B, which constrains electron motion; 3) the diffusion length of the hot carriers at interfaces and the edges, which dictates energy relaxation, and 4) the periodicities of superlattices induced by moiré engineering, which defines the energy scale of emerging quantum phases. For instance, the commensurability of the magnetic lengths (~10 nm for graphene at 7T) and superlattice constant (~10 nm for twisted bilayer graphene at "magic" angle) would give rise to exotic fractal quantum states. In this talk, I will present: 1) A cutting-edge optical spectroscopy technique, Landau-level nanoscopy, capable of simultaneously probing all four critical length scales in a single experiment; 2) the discovery of classes of infrared polaritons that can be tuned by magnetic fields, enhancing our ability to manipulate light-matter interactions and probe many-body physics at the nanoscale; 3) nanoscale mapping of thermoelectric properties in the quantum Hall bulk, revealing strong violations of the Wiedemann-Franz law. Our approach establishes Landau-level nanoscopy as a versatile platform for investigating magneto-optical effects and many-body interactions at the nanoscale.

Keywords: s-SNOM; 2D materials; quantum hall; polaritons; strong light matter interaction