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Q: Fachverband Quantenoptik und Photonik

Q 3: Photonics I

Q 3.5: Vortrag

Montag, 10. März 2025, 12:15–12:30, HS Botanik

Topological phase transition in non-Hermitian gauge fields — •Bikashkali Midya — Indian Institute of Science Education and Research Berhampur, India

We will describe the point-gap topological phase transitions and skin-effect in non-Hermitian photonic lattice models. These models incorporate site-dependent nonreciprocal hoppings facilitated by a spatially fluctuating complex gauge field that disrupts translational symmetry. We propose a analytical framework that offers a comprehensive method for analytically predicting spectral topological invariance and associated boundary localization phenomena for bond-disordered nonperiodic lattices, based on imaginary gauge-transformed mean-field periodic lattices. Notably, for a lattice with quasiperiodic gauge-field g = log |λ cos 2πα n | and an irrational previously unknown topological phase transition is unveiled. It is observed that the topological spectral index W assumes values of -N or +N, leading to all N open-boundary eigenstates localizing either at the right or left edge, solely dependent on the strength of the gauge field, where λ<2 or λ>2. A phase transition is identified at the critical point undergo delocalization. The theory has been shown to be relevant for long-range hopping models λ = 2, at which all eigenstates undergo delocalization.

Keywords: Topological localization; Imaginary gauge field; non-Hermitian skin effect; Photonic lattice