Magnetic skyrmions are tiny, topologically quantized magnetic whirls stabilized by relativistic spin-orbit interactions. They couple extremely efficiently to charge-, spin- and heat currents and can be manipulated by ultra small forces. They are therefore promising candidates for, e.g., future magnetic memories. The coupling of skyrmions to electrons can efficiently be described by artifical electromagnetic fields. We explore how these fields can be measured. Phase transitions in and out of the skyrmion phase are driven by topological point defects which can be identified as emergent magnetic monopoles.

Ultracold quantum gases are usually well isolated from the environment. This allows for the study of ground state properties and non-equilibrium dynamics of many-body quantum systems under almost ideal conditions. Introducing a controlled coupling to the environment “opens” the quantum system and non-unitary dynamics can be investigated. Such an approach provides new opportunities to study fundamental quantum phenomena and to engineer robust many-body quantum states. I will present an experimental platform [1,2] that allows for the controlled engineering of dissipation in ultracold quantum gases by means of localized particle losses. This is exploited to study quantum Zeno dynamics in a Bose-Einstein condensate [3], where we find that the particle losses are well described by an imaginary potential in the system’s Hamiltonian. We also investigate the steady-states in a driven-dissipative Josephson array [4]. For small dissipation, the steady-states are characterized by balanced loss and gain and the eigenvalues are real. This situation corresponds to coherent perfect absorption [5], a phenomenon known from linear optics. Above a critical dissipation strength, the system decays exponentially, indicating the existence of purely imaginary eigenvalues. We discuss our results in the context of dissipative phase transitions. References [1] T. Gericke et al., Nature Physics 4, 949 (2008). [2] P. Würtz et al., Phys. Rev. Lett. 103, 080404 (2009). [3] G. Barontini et al., Phys. Rev. Lett. 110, 035302 (2013). [4] R. Labouvie et al. Phys. Rev. Lett. 116, 235302 (2016). [5] A. Müllers et al. Science Advances 4, eaat6539 (2018).