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UID:UW-Physics-Event-8283
DTSTART:20230608T150000Z
DTEND:20230608T230000Z
DTSTAMP:20260414T033132Z
LAST-MODIFIED:20230530T124012Z
LOCATION:5310 Chamberlin
SUMMARY:Diode effects in current-biased Josephson junctions\, R. G. He
 rb Condensed Matter Seminar\, Jacob F. Steiner\, Caltech
DESCRIPTION:Current-biased Josephson junctions exhibit hysteretic tran
 sitions between dissipative and superconducting states as characterize
 d by switching and retrapping currents. Common lore says that these cu
 rrents become nonreciprocal (i.e.\, they depend on the direction of th
 e bias current) if both time-reversal and inversion symmetry are absen
 t. This so-called Josephson diode effect is used to experimentally pro
 be for spontaneous time-reversal symmetry breaking. Recently\, however
 \, a Josephson diode effect was observed in a time-reversal symmetric 
 Josephson junction involving a single magnetic adatom [1]. To resolve 
 this apparent conflict\, we develop a theory for diodelike effects in 
 the switching and retrapping currents of weakly damped Josephson junct
 ions. We find that while the diodelike behavior of switching currents 
 is rooted in asymmetric current-phase relations\, nonreciprocal retrap
 ping currents originate in asymmetric dissipative currents. These diff
 erent origins also imply distinctly different symmetry requirements: c
 urrent-phase asymmetry requires broken time-reversal symmetry\, in con
 trast asymmetric dissipation stems from broken particle-hole symmetry.
  In the case of magnetic-atom Josephson junctions the latter may be tr
 aced back to Yu-Shiba-Rusinov subgap states. While our theory [2] was 
 inspired by the experiment [1]\, it relies on general principles only\
 , and may provide significant guidance in identifying the microscopic 
 origin of nonreciprocities in any Josephson junction.
\n 
\nReferences
 :
\n[1] Trahms et al. Nature 615 (2023)  
\n[2] Steiner et al. PRL 130
  (2023)
URL:https://www.physics.wisc.edu/events/?id=8283
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