Hannover 2016 – scientific programme

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A: Fachverband Atomphysik

A 23: Ultra-cold atoms, ions and BEC I (with Q)

A 23.8: Talk

Wednesday, March 2, 2016, 12:45–13:00, f107

Nontrivial topological phases in quantum mechanical many-body systems with gain and loss effects — •Marcel Klett, Holger Cartarius, and Günter Wunner — 1. Institut für Theoretische Physik, Universität Stuttgart, 70550 Stuttgart

Non-Hermitian PT-symmetric potentials are capable of effectively describing quantum systems with balanced in- and outfluxes. They allow for the existence of a PT-symmetric phase with purely real energy spectra of the non-Hermitian Hamiltonian. Good candidates for the realization of a genuine PT-symmetric quantum system are Bose-Einstein condensates. Recently a possible relation between the appearance of the PT-symmetric phase and topologically nontrivial states were found in two studies of simple model systems. However, they came to opposite conclusions. In the Su-Schrieffer-Heeger (SSH) model [1] the topological phase has a major influence. As soon as topologically nontrivial states appear PT symmetry gets broken. This is in contrast to the non-Hermitian Kitaev model [2], in which PT symmetry breaking does not depend on the topological phase. Our work is based on including different non-Hermitian potentials in the SSH model as well as the Kitaev model. We perform exact calculations of the eigenvalues and the eigenstates, clarify the relation between PT symmetry and topological phases, and explain why opposite results were found in the above mentioned systems. Consequences for PT-symmetric Bose-Einstein condensates are discussed.

[1] Baogang Zhu et al., Phys. Rev. A 89, 062102 (2014)*

[2] Xiaohui Wang et al., Phys. Rev. A 92, 012116 (2015)