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DY: Fachverband Dynamik und Statistische Physik

DY 19: Quantum Chaos

DY 19.2: Vortrag

Mittwoch, 24. März 2010, 14:30–14:45, H38

Geometric Phases of Exceptional Points in Time-Reversal Noninvariant Systems — Stefan Bittner¹, Barbara Dietz-Pilatus¹, Pedro Oria Iriarte¹, Maksim Miski-Oglu¹, Achim Richter^1,3, Hans A. Weidenmüller², Hanns L. Harney², and •Florian Schäfer^1,4 — ¹Institut für Kernphysik, Schlossgartenstraße 9, 64289 Darmstadt — ²Max-Planck-Institut für Kernphysik, 69029 Heidelberg — ³ECT^*, Villa Tambosi, I-38100 Villazzano (Trento), Italy — ⁴LENS, University of Florence, I-50019 Sesto-Fiorentino (Firenze), Italy

The eigenvectors of a two level system described by a non-Hermitian Hamiltonian coalesce at a so-called Exceptional Point, a phenomenon already investigated in numerous systems. In general, for a two-dimensional Hamiltonian the two components of each eigenfunction define an enclosing angle φ. Past experiments established for time-reversal invariant systems at an Exceptional Point a universal phase φ=π. Here, we present results on experiments in microwave billiards with partial time-reversal invariance violation, induced by the presence of a magnetized ferrite. Two control parameters allow for a variation of the Hamiltonian. The experiments explore the parameter space in vicinity the of and at an Exceptional Point. The data allow for a reconstruction of the complete, complex-valued Hamiltonian. Using this information we demonstrate a sensitive dependence of φ at an Exceptional Point on the strength of time-reversal invariance violation.

This work is supported by DFG through SFB 634.