Am Montag, den 15. Juli 2024, um 12:00 Uhr c.t., findet der nächste Termin unseres Physikalischen Kolloquiums statt.
Referent ist Prof Carlos A. R. Sa de Melo vom Georgia Institute of Technology zum Thema FROM BARDEEN-COOPER-SCHRIEFFER (BCS) PAIRING TO BOSE-EINSTEIN CONDENSATION (BEC) IN METALS, NEUTRON STARS, NUCLEI, AND ULTRACOLD ATOMS
Superfluidity and superconductivity are very interesting many-body phenomena that have been found in metals, neutron stars,
nuclei and more recently in ultracold atoms. [1] For a given metal, neutron star, or nuclei the tunability of particle density or
interaction strength is either very limited or impossible, and thus many density- or interaction-dependent superfluid/
superconducting properties cannot be controlled at the turn of a knob. However, in ultracold Fermi atoms the interaction
strength can be tuned experimentally to change qualitatively and quantitatively superfluid properties. This tunability allows for
the study of the evolution of superfluidity from Bardeen-Copper-Schrieffer (BCS, weak coupling) of large Cooper pairs to Bose-
Einstein condensation (BEC, strong coupling) of tightly bound molecules. I discuss the BCS to BEC evolution in s-wave [2]
and p-wave [3] angular momentum channels and conclude that this evolution is just a crossover phenomenon for s-wave,
while it corresponds to a quantum phase transition for p-wave pairing. Lastly, I consider condensed matter systems (Li-doped
nitrates and magic angle twisted trilayered graphene), where particle density or chemical potential may be tuned
experimentally, potentially allowing for studies of the BCS (high density) to BEC (low density) evolution in superconductors. [4][1] C. A. R. Sá de Melo, “When fermions become bosons: Pairing in ultracold gases”, Physics Today 61 (10), 45-51 (2008). [2] C. A. R. Sá
de Melo, Mohit Randeria, Jan R. Engelbrecht, “Crossover from BCS to Bose superconductivity: Transition temperature and time-
dependent Ginzburg-Landau theory”, Phys. Rev. Lett. 71, 3202 (1993). [3] M. Iskin and C. A. R. Sá de Melo, “Evolution from BCS to BEC
superfluidity in p-wave Fermi gases, Phys. Rev. Lett. 96, 040402 (2006). [4] C. A. R. Sá de Melo and Senne Van Loon, “Evolution from
Bardeen-Cooper-Schriefer to Bose-Einstein Condensation in two dimensions: Crossovers and topological quantum phase transitions”,
Annual Review of Condensed Matter Physics 15, 109-129 (2024).
Abstract des Vortrags von Prof Carlos A. R. Sa de Melo
Die Einführung erfolgt durch Ilya Eremin
Die Fakultät lädt alle Interessierten herzlich ein. Die
Veranstaltung findet im Hörsaal HNB statt
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