November 2022

Abstracts of the QSIT/Quantum Center, ETH Zurich Lunch Seminar

Date: Thursday, November 3, 2022
Place: ETH Zurich, Hönggerberg, HPF G6
Time: 12:00 - 13:00

Kinetic Magnetism in Moiré Heterostructures

Livio Ciorciaro - Quantum Photonics Group (Imamoglu group), ETH Zurich

Moiré heterostructures of layered van-der-Waals crystals have proven to be a rich platform for studying correlated electrons in 2D. Here, we focus on the magnetic order of an electron-doped heterostructure described by a Fermi-Hubbard model on a triangular lattice. Experiments show evidence of a transition from antiferromagnetic to ferromagnetic interactions around a doping of one electron per site. I will discuss the mechanism behind this transition and show the evidence of its realization from optical measurements in a MoSe2/WS2 heterostructure.

Spin-Holstein Models in Trapped-Ion Systems

Johannes Knörzer - Theoretical Condensed Matter Physics (Demler group) and Institute for Theoretical Studies (ITS), ETH Zurich

Quantum simulators are a fascinating playground for exploring quantum many-body physics. There are several physical platforms for performing analogue quantum simulations, each coming with their own advantages. Trapped ion quantum simulators have several key features, and among them is the possibility to realise a variety of spin models, where ion spins couple to lattice vibrations. In this talk, I will discuss recent work on spin-phonon models that can be realised with trapped ions [1]. There we highlight how trapped-ion quantum systems can be used to study generalized Holstein models, and benchmark expensive numerical calculations. We study a particular spin-Holstein model that can be implemented with arrays of ions confined by individual microtraps, and that is closely related to the Holstein model of condensed matter physics, used to describe electron-phonon interactions. In contrast to earlier proposals, we focus on simulating many-electron systems and inspect the competition between charge-density wave order, fermion pairing, and phase separation. In our numerical study, we employ a combination of complementary approaches, based on non-Gaussian variational ansatz states and matrix product states, respectively. We demonstrate that this hybrid approach outperforms standard density-matrix renormalization group calculations.

[1] JK, T. Shi, E. Demler, J. I. Cirac, Phys. Rev. Lett. 128, 120404 (2022).