Regensburg 2025 – scientific programme

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TT: Fachverband Tiefe Temperaturen

TT 53: Topology: Other Topics

TT 53.5: Talk

Friday, March 21, 2025, 10:30–10:45, H32

Topological Properties of the Non-Reciprocal α-Diamond Chain — Carolina Martinez-Strasser¹ and •Dario Bercioux^1,2 — ¹Donostia International Physics Center (DIPC), 20018 Donostia-San Sebastián, Spain — ²Ikerbasque, Basque Foundation for Science, Plaza Euskadi 5 48009 Bilbao, Spain

This work explores the topological properties of a generalized non-Hermitian quasi-1D lattice, dubbed as the non-reciprocal α-diamond chain. The diamond chain is a tripartite lattice featuring three sites per unit cell, characterized by a flat band at zero energy associated with compact localized states, and topological edges edge states in the Hermitian and non-Hermitian regimes [1,2]. Building upon our previous investigations [2], we extend the analysis to a more general framework by introducing an α-parameter, quantifying the non-reciprocal hopping strength in the lower part of the diamond chain. Our generalization reveals a spectrum of non-Hermitian phenomena, including exceptional points of order 3 (EP3s) under specific parameter tuning. These EP3s, where three eigenvalues and their eigenvectors coalesce, offer valuable insights into the behavior of three-band non-Hermitian systems. The α-diamond chain thus serves as an effective 1D platform for exploring such phenomena, particularly in the presence of sublattice symmetries [3].

[1] Bercioux et al., Ann. Phys. 529, 1600262 (2017).

[2] Martinez-Strasser et al., Adv.Quantum.Technol.7,2300225(2023).

[3] Montag and Kunst, Phys. Rev. Res. 6, 023205 (2024).

Keywords: non-Hermitian; non-reciprocal; exceptional point