Observation of a pairing pseudogap in a two-dimensional Fermi gas

TL;DR

This study observes a pairing pseudogap in a two-dimensional ultracold Fermi gas, providing insights into high-temperature superconductivity and many-body pairing phenomena in reduced dimensions.

Contribution

It reports the first direct detection of a many-body pairing gap above the superfluid transition in a 2D Fermi gas using momentum-resolved spectroscopy.

Findings

Detection of a pairing gap above the superfluid transition temperature

Observation of many-body pairing in a strongly interacting 2D Fermi gas

Advancement in emulating layered superconductors with ultracold atoms

Abstract

Pairing of fermions is ubiquitous in nature and it is responsible for a large variety of fascinating phenomena like superconductivity, superfluidity of $^3$He, the anomalous rotation of neutron stars, and the BEC-BCS crossover in strongly interacting Fermi gases. When confined to two dimensions, interacting many-body systems bear even more subtle effects, many of which lack understanding at a fundamental level. Most striking is the, yet unexplained, effect of high-temperature superconductivity in cuprates, which is intimately related to the two-dimensional geometry of the crystal structure. In particular, the questions how many-body pairing is established at high temperature and whether it precedes superconductivity are crucial to be answered. Here, we report on the observation of pairing in a harmonically trapped two-dimensional atomic Fermi gas in the regime of strong coupling. We perform momentum-resolved photoemission spectroscopy, analogous to ARPES in the solid state, to measure the spectral function of the gas and we detect a many-body pairing gap above the superfluid transition temperature. Our observations mark a significant step in the emulation of layered two-dimensional strongly correlated superconductors using ultracold atomic gases.