Szemináriumok
Generative neural network for quantum correlations
Komplex mágnesség és magneto-szupravezetés első elvekből
Weak vs. strong breaking of integrability in interacting scalar quantum field theories
Thermodynamics, transport, and fluctuations in the sine-Gordon model
Protocols to measure the non-Abelian Berry phase by pumping a spin qubit through a quantum-dot loop
Classification and magic magnetic-field directions for spin-orbit-coupled double quantum dots
Fast simultaneous 3D acousto-optical imaging and photostimulation for visual restoration
Singularity theory of Weyl-point creation and annihilation
Weyl points (WP) are robust spectral degeneracies, which can not be split by small perturbations, as they are protected by their non-zero topological charge. For larger perturbations, WPs can disappear via pairwise annihilation, where two oppositely charged WPs merge, and the resulting neutral degeneracy disappears. The neutral degeneracy is unstable, meaning that it requires the fine-tuning of the perturbation. Fine-tuning of more than one parameter can lead to more exotic WP mergers. In this work [1], we reveal and analyze a fundamental connection of the WP mergers and singularity theory: phase boundary points of Weyl phase diagrams, i.e., control parameter values where Weyl point mergers happen, can be classified according to singularity classes of maps between manifolds of equal dimension. We demonstrate this connection on a Weyl--Josephson circuit where the merger of 4 WPs draw a swallowtail singularity, and in a random BdG Hamiltonian which reveal a rich pattern of fold lines and cusp points. Our results predict universal geometrical features of Weyl phase diagrams, and generalize naturally to creation and annihilation of Weyl points in electronic (phononic, magnonic, photonic, etc) band-structure models, where Weyl phase transitions can be triggered by control parameters such as mechanical strain.
Spintronics: its evolution and the case for low symmetry materials
In this seminar I will revise some milestones in spintronics, the discipline which develops electronics with the use of the spin of the electron. I will highlight ultra-sensitive magnetic sensors and memory devices, whose commercial success have led to more advance proposals such as memory-in-logic. I will then present some current experiments in which we make use of low symmetry materials for unleashing unexpected spin phenomena.