Thema der Disputation:
Interacting quantum spins with periodic, quasiperiodic and directcurrent drives
Interacting quantum spins with periodic, quasiperiodic and directcurrent drives
Abstract: Driving challenges the established equilibrium paradigms of interacting quantum many-body systems. In the driven setting, interactions between the particles play a key role that may steer quantum systems into non-equilibrium phases of matter without equilibrium counterparts. This thesis explores quantum spins in the presence of periodic, quasi-periodic and direct-current drives. We begin with Majorana zero modes (MZMs) and Majorana π modes (MPMs) in the Floquet quantum Ising model. In the presence of symmetry-breaking random fields, boundary spin correlations associated with MZMs and MPMs display markedly different behavior. We show that this can be understood from the perspective of Majorana-induced pairings in the many-body spectrum. This spectral viewpoint of paired levels also applies to the paradigmatic Floquet time crystal with strong disorder, allowing to derive analytical expressions for temporal spin correlations. Next, we study a quantum Ising chain under quasi-periodic Fibonacci drive and map out its phase diagram. The boundary of the spin chain can host Majorana golden-ratio modes (MGMs) unique to the quasi-periodic setting. Finally, we turn to magnetic impurities in superconductors. We treat the spins of a Yu-Shiba-Rusinov dimer fully quantum, accounting for the complex interplay of screening, superconducting correlations, magnetic anisotropies and substrate-mediated interactions. The dimer reveals rich phases and excitation spectra which underscore the role of interactions between spins under direct-current driving.
Zeit & Ort
24.07.2025 | 15:30
Hörsaal B (0.1.01)
(Fachbereich Physik, Arnimallee 14, 14195 Berlin)