Selective Population of Edge States in a 2D Topological Band System

We consider a system of interacting spin-one atoms in a hexagonal lattice under the presence of a synthetic gauge field. Quenching the quadratic Zeeman field is shown to lead to a dynamical instability of the edge modes. This, in turn, leads to a spin current along the boundary of the system which grows exponentially fast in time following the quench. Tuning the magnitude of the quench can be used to selectively populate edge modes of different momenta. Implications of the intrinsic symmetries of Hamiltonian on the dynamics are discussed. The results hold for atoms with both antiferromagnetic and ferromagnetic interactions.Comment: 7 pages (expanded Supplemental Material

Impact of the strong electromagnetic field on the QCD effective potential for homogeneous Abelian gluon field configurations

The one-loop quark contribution to the QCD effective potential for the homogeneous Abelian gluon field in the presence of external strong electromagnetic field is evaluated. The structure of extrema of the potential as a function of the angles between chromoelectric, chromomagnetic and electromagnetic fields is analyzed. In this setup, the electromagnetic field is considered as an external one while the gluon field represents domain structured nonperturbative gluon configurations related to the QCD vacuum in the confinement phase. Two particularly interesting gluon configurations, (anti-)self-dual and crossed orthogonal chromomagnetic and chromoelectric fields, are discussed specifically. Within this simplified framework it is shown that the strong electromagnetic fields can play a catalysing role for a deconfinement transition. At the qualitative level, the present consideration can be seen as a highly simplified study of an impact of the electromagnetic fields generated in relativistic heavy ion collisions on the strongly interacting hadronic matter.Comment: 9 pages, 4 figure

Topological spin dynamics in 2D Bose Lattices

This thesis presents theoretical work devoted to the manifestation of the edge states of boson topological band insulators in optical lattice experiments with weakly-interacting spinor condensates. Although the investigation is presented mainly on a spin-one Kane-Mele model, many aspects of this thesis can be generalised to other lattice models. One major question this thesis addresses is the relevance of topological edge states in the dynamics of the interacting boson systems. This thesis shows how interactions in quenched spinor condensates can facilitate the manifestation of the edge states of two dimensional topological lattice models. Provided certain quench and symmetry-related conditions are fulfilled, the edge states are found to be populated exponentially fast right after the quench. A growing edge spin current is also described. A preliminary numerical computation for later times suggests a particle redistribution from the edge back into the bulk. The presence of a harmonic potential in optical lattice experiments often obscures the manifestation of the edge states. In relation to this problem, spinor condensates have been considered, and a sharpening of the boundaries is observed in the Thomas-Fermi regime. Moreover, for spin-$\pm1$ states, despite the presence of the external potential, one can recover a band structure similar to that of a non-interacting model with hard-wall boundaries. Approximate analytical expressions for the edge-state energies in the presence of a harmonic potential are derived. The results presented in this thesis aim to widen the understanding of the manifestation of boson topological edge states, and are in line with the current experiments with ultracold atoms. The thesis suggests mechanisms of experimentally probing boson topological edge states and their quench dynamics with spinor condensates.Open Acces

Long-lived elementary excitations and light coherence in topological lasers

Combining topologically-protected chiral light transport and laser amplification gives rise to topological lasers, whose operation is immune to fabrication imperfections and defects, uncovering the role of topology in a novel nonlinear non-Hermitian regime. We study a topological laser based on the photonic Haldane model with selective pumping of chiral edge modes described by saturable gain. We investigate elementary excitations around the mean-field steady state and their consequences for the coherence properties. In particular, we show that the hybridization of chiral edge modes gives rise to long-lived elementary excitations, leading to large phase fluctuations in the emitted light field and a decrease of light coherence. In contrast to topologically trivial lasers, the lifetime of elementary excitations is robust against disorder in topological lasers. However, the lifetime strongly depends on the edge-mode dispersion around the lasing frequency. As a result, the lifetime can be reduced by orders of magnitude for lasing of different edge modes, leading to a suppression of phase fluctuations and larger coherence of the emitted light. On the other hand, amplitude fluctuations and the second-order autocorrelation function are moderately increased at the same time.European Union’s Horizon 2020 research and innovation programme under grant agreement No 732894 (FET Proactive HOT), Royal Society (University Research Fellowship), Winton Programme for the Physics of Sustainabilit