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SUMMARY:The Evolution from BCS to BEC in Superfluids and Superconductors: 
 Crossovers versus Quantum Phase Transitions
DTSTART:20260619T111500Z
DTEND:20260619T130000Z
DTSTAMP:20260618T104900Z
UID:indico-event-1470@indico.hiskp.uni-bonn.de
DESCRIPTION:Speakers: Carlos Sá de Melo (Georgia Institute of Technology\
 , USA)\n\nSuperfluidity and superconductivity are interesting many-body ph
 enomena that have been found in metals\, neutron stars\, nuclei and more r
 ecently in ultracold atoms. [1] For a given metal\, neutron star\, or nucl
 ei the tunability of particle density or interaction strength is either ve
 ry limited or impossible\, and thus many density- or interactiondependent 
 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 superf
 luid properties. This tunability allows for the study of the evolution of 
 superfluidity from Bardeen-CopperSchrieffer (BCS\, weak coupling) of large
  Cooper pairs to Bose-Einstein condensation (BEC\, strong coupling) of tig
 htly 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 (higher density) to BEC (low
 er density) evolution in superconductors. [4]\n[1] C. A. R. Sá de Melo\, 
 “When fermions become bosons: Pairing in ultracold gases”\, Physics To
 day 61 (10)\, 45-51 (2008).\n[2] C. A. R. Sá de Melo\, Mohit Randeria\, J
 an R. Engelbrecht\, “Crossover from BCS to Bose superconductivity: Trans
 ition temperature and time-dependent Ginzburg-Landau theory”\, Phys. Rev
 . Lett. 71\, 3202 (1993).\n[3] M. Iskin and C. A. R. Sá de Melo\, “Evol
 ution from BCS to BEC superfluidity in p-wave Fermi gases\, Phys. Rev. Let
 t. 96\, 040402 (2006).\n[4] C. A. R. Sá de Melo and Senne Van Loon\, “E
 volution from Bardeen-Cooper-Schriefer to Bose-Einstein Condensation in tw
 o dimensions: Crossovers and topological quantum phase transitions”\, An
 nual Review of Condensed Matter Physics 15\, 109-129 (2024).\n\nhttps://in
 dico.hiskp.uni-bonn.de/event/1470/
LOCATION:Käthe-Kümmel-Str. 1/0.056 (ROT) - Lecture Hall (ROT)
URL:https://indico.hiskp.uni-bonn.de/event/1470/
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