News from the Lab 2020

Dec. 17 at 10:15 online (Zoom): Group seminar
Speaker: Tobias Busse | Title: Analysis of the Symmetry Structure in the strongly-interacting Majorana Hubbard Model on the Honeycomb Lattice | Abstract: The broad progress, experimentally and theoretically, in proposing and realizing models of unpaired Majoranas lead to a substantial interest and research activity in the field. While phases of matter of strongly-interacting electrons have been studied for decades, new phenomena which may arise from interacting Majoranas are mostly ongoing research. In this talk I will present you our work on the strongly-interacting Majorana-Hubbard model on the Honeycomb lattice. I will give a short introduction to level statistics in random matrix theory which is an established tool to distinguish between chaotic and integrable quantum systems. Motivated by the urge to find irreducible sectors of the Hamiltonian whose level statistics would reveal an integrable or chaotic nature we investigate in depth the symmetries of the Model by using analytical and numerical methods. We work with a spin Hamiltonian on a triangular lattice that is obtained by a Jordan-Wigner transformation of the Majorana Hamiltonian. The symmetry structure of the Hamiltonian is rich and the interplay of anticommuting symmetry operators leads to a degeneracy that is dependent on whether there is a shear at the periodic boundaries. | See you online!
Dec. 03 at 10:15 online (Zoom): Group seminar
Talk by Stefan Oleschko | Title: Analogue quantum simulation using superconducting qubits | Abstract: In this talk I want to present the research activities of the superconducting quantum circuits group of Gerhard Kirchmair in Innsbruck. I will show how we want to use 3D circuit QED architectures to realize a platform for quantum many body simulations of dipolar XY models on 2D lattices using state of the art circuit QED technology. The central idea is to exploit the naturally occurring dipolar interactions between 3D superconducting qubits to simulate models of interacting quantum spins. The ability to arrange the qubits in essentially arbitrary geometries allows us to design spin models with more than nearest-neighbor interaction in various geometries. Furthermore, I want to emphasise the unique tools of circuit QED to investigate spin-systems. | See you online!
Nov. 26 at 10:15 online (Zoom): Group seminar
Talk by Lukas Sieberer | Title: Entanglement Spectrum Crossings Reveal non-Hermitian Dynamical Topology | Abstract: The development of non-Hermitian topological band theory has led to observations of novel topological phenomena in effectively classical, driven and dissipative systems. However, for open quantum many-body systems, the absence of a ground state presents a challenge to define robust signatures of non-Hermitian topology. In my talk, I will show that such a signature is provided by crossings in the time evolution of the entanglement spectrum. These crossings occur in quenches from the trivial to the topological phase of a driven-dissipative Kitaev chain that is described by a Markovian quantum master equation in Lindblad form. At the topological transition, which can be crossed either by changing parameters of the Hamiltonian of the system or by increasing the strength of dissipation, the time scale at which the first entanglement spectrum crossing occurs diverges with a universal dynamical critical exponent. These numerical findings are corroborated with an exact analytical solution of the quench dynamics for a spectrally flat postquench Liouvillian. The exact solution suggests an interpretation of the topological quench dynamics as a fermion parity pump. The results I will present thus reveal signatures of non-Hermitian topology that are unique to quantum many-body systems and cannot be emulated in classical simulators of non-Hermitian wave physics. | See you online!
Oct. 30: Elisa Brunori "Supervised Learning with Matrix Product States" (Defensio Master)
Supervisor: Univ.-Prof. Dr. Andreas Läuchli
Sep. 29: Patrick Wilhelm "Charge-density-wave order and kinetic stabilization of correlated phases in fractionally filled Chern bands of twisted bilayer graphene" (Defensio Master)
Supervisor: Univ.-Prof. Dr. Andreas Läuchli
Sep. 25: Michael Rader "Tensor Network State Methods and Applications for Strongly Correlated Quantum Many-Body Systems" (Defensio Dissertation)
Supervisor: Univ.-Prof. Dr. Andreas Läuchli
Sep. 01: Tenure track position for Mathias Scheurer
We are happy to welcome Mathias in our research group AG Läuchli at the Institute for Theoretical Physics. Mathias joined our team on 1st of September 2020 and holds a tenure track position for quantum many-body physics. He is currently building up his own research group called "Quantum Condensed Matter: From Field theory to Machine Learning".

News from the Department

Further news are available on the German website