Understanding the origins of unconventional superconductivity has been a major focus of condensed matter physics for many decades. While many questions remain unanswered, experiments have found the highest critical temperatures in layered two-dimensional materials. However, to what extent the remarkable stability of these strongly correlated 2D superfluids is affected by their reduced dimensionality is still an open question. Here, we use dilute gases of ultracold fermionic atoms as a model system to directly observe the influence of dimensionality on the stability of strongly interacting fermionic superfluids. We find that the superfluid gap follows the same universal function of the interaction strength regardless of dimensionality, which suggests that there is no inherent difference in the stability of two- and three-dimensional fermionic superfluids. Finally, we compare our data to results from solid state systems and find a similar relation between the interaction strength and the gap for a wide range of two- and three-dimensional superconductors.
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http://dx.doi.org/10.1103/PhysRevLett.129.083601 | DOI Listing |
Nat Commun
January 2025
CNR Nanotec, Institute of Nanotechnology, via Monteroni, 73100, Lecce, Italy.
Macroscopic coherence in quantum fluids allows the observation of interference effects in their wavefunctions, and enables applications such as superconducting quantum interference devices based on Josephson tunneling. The Josephson effect manifests in both fermionic and bosonic systems, and has been well studied in superfluid helium and atomic Bose-Einstein condensates. In exciton-polariton condensates-that offer a path to integrated semiconductor platforms-creating weak links in ring geometries has so far remained challenging.
View Article and Find Full Text PDFPhys Rev Lett
November 2024
Institute for Quantum Electronics and Quantum Center, ETH Zürich, 8093 Zürich, Switzerland.
The formation of dark states is an important concept in quantum sciences, but its compatibility with strong interparticle interactions-for example, in a quantum degenerate gas-is hardly explored. Here, we realize a dark state in one of the spins of a two-component, resonantly interacting Fermi gas using a Λ system within the D_{2} transitions of ^{6}Li at high magnetic field. The dark state is created in a micrometer-sized region within a one-dimensional channel connecting two superfluid reservoirs.
View Article and Find Full Text PDFNat Commun
October 2024
Department of Physics and Research Center OPTIMAS, RPTU Kaiserslautern-Landau, Kaiserslautern, Germany.
The microscopic pair structure of superfluids has profound consequences on their properties. Delocalized pairs are predicted to be less affected by static disorder than localized pairs. Ultracold gases allow tuning the pair size via interactions, where for resonant interaction superfluids show largest critical velocity, i.
View Article and Find Full Text PDFPhys Rev Lett
October 2024
Physikalisches Institut, University of Bonn, Wegelerstraße 8, 53115 Bonn, Germany.
Nat Phys
April 2024
Institute for Quantum Electronics & Quantum Center, ETH Zurich, Zurich, Switzerland.
The nature of particle and entropy flow between two superfluids is often understood in terms of reversible flow carried by an entropy-free, macroscopic wavefunction. While this wavefunction is responsible for many intriguing properties of superfluids and superconductors, its interplay with excitations in non-equilibrium situations is less understood. Here we observe large concurrent flows of both particles and entropy through a ballistic channel connecting two strongly interacting fermionic superfluids.
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