Regensburg 2025 – scientific programme
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HL: Fachverband Halbleiterphysik
HL 29: Poster II
HL 29.23: Poster
Tuesday, March 18, 2025, 18:00–20:00, P1
Probing time-reversal symmetry breaking in graphene — •Konrad Krieghoff1, Nele Tornow1, Omid Ghaebi1, and Giancarlo Soavi1, 2 — 1Institute of Solid State Physics, Friedrich Schiller University Jena, Jena, Germany — 2Abbe Center of Photonics, Friedrich Schiller University Jena, Jena, Germany
In graphene, space inversion symmetry (SIS) and time-reversal symmetry (TRS) combined with a hexagonal lattice give rise to a linear band dispersion at the +/−K points of the Brillouin zone. Breaking TRS can result in exotic phenomena, such as the realization of the Haldane model and the photoinduced anomalous quantum Hall effect. Thanks to its high sensitivity to changes in the crystal symmetry, nonlinear optical spectroscopy provides an excellent tool to study these effects.
In our work, we use an elliptically polarized laser beam to excite monolayer graphene, where the circular polarization component breaks TRS. This symmetry breaking induces new nonzero elements in the third-order nonlinear susceptibility tensor, which are then probed by the linear component of the excitation beam. The combination of the already existing and the light induced tensor elements results in a rotation of the emitted third harmonic signal. Preliminary experimental results further indicate an impact of both excitation power and doping of the sample. Since SIS is still intact, our approach offers a new method for exploring broken TRS and topology in centrosymmetric materials.
Keywords: Graphene; Nonlinear optics; Time-reversal symmetry