Kiefer, Yann

Date:    Wednesday, August 30, 2023 
Time:    14:00
Place:    ETH Campus Hönggerberg, HPV G 4
Host:    Tilman Esslinger

Ultracold Feshbach molecules in an orbital optical lattice

Yann Kiefer –  University of Hamburg, Germany

Abstract: The mechanisms of high-TC superconductors (SCs) are arguably still one of the biggest open problems of modern physics. It was quickly realized that pairing mechanisms in unconventional SCs cannot be described by conventional BCS theory, where the pairing of two electrons is mediated by the phononic excitations of the ionic background. It is known today, that one of the relevant degrees of freedom in the context of unconventional pairing mechanisms is the orbital structure of the electron clouds inside the crystalline lattice [1]. In my talk „Ultracold Feshbach molecules in an orbital optical lattice“, I will demonstrate how we investigate related phenomena with the first realization of an experimental platform combining the access to three key properties to approach a most realistic scenario: fermionic quantum statistics, interaction mediated pairing and non-trivial orbital degree of freedom. I will demonstrate how we create Feshbach molecules in selected excited Bloch Bands of an optical square lattice and measure binding energies and half lives with a novel technique resembling mass spectrometry [2].

I will start the talk with a general introduction to analogue quantum simulation [3] in the context of optical lattice experiments to showcase the impressive toolbox that was developed for cold atom experiments. In the following, I will introduce our specific, unique experimental setup allowing for efficient excitation of particles to excited Bloch bands of a bipartite optical square lattice with non-trivial orbital degree of freedom [4]. Then, I will explain in detail how homonuclear, bosonic Feshbach molecules consisting of two fermions are created in presence of strong optical confinement and introduce a dissociation protocol resembling mass spectrometry. Subsequently, I will present binding energy measurements for a large range of magnetic fields together with a theoretical model for binding energies in dependence of the external magnetic field. In the last part of my talk, I will present half-live measurements for three different optical traps over a large range of interactions. From these measurements we determine two different regimes, in which the relaxation processes are dominated by different mechanisms and compare our findings with existing theoretical work.