BEGIN:VCALENDAR
VERSION:2.0
PRODID:-//Talks.cam//talks.cam.ac.uk//
X-WR-CALNAME:Talks.cam
BEGIN:VEVENT
SUMMARY:New insights at ultra-low temperatures: superconductivity and nucl
 ear-electronic quantum criticality - Prof. Alix McCollam\, School of Physi
 cs\, University College Cork\, Ireland
DTSTART:20240222T111500Z
DTEND:20240222T123000Z
UID:TALK212101@talks.cam.ac.uk
CONTACT:Malte Grosche
DESCRIPTION:Many strongly correlated electron systems develop ordered phas
 es at low temperatures that can be well\nunderstood in terms of an electro
 nic order parameter. At ultra-low temperatures\, however\, the hyperfine\n
 interaction between nuclei and electrons becomes increasingly important\, 
 and we have to consider how\nthis affects ordered phases and phase transit
 ions close to T = 0.\nPrOs4Sb12 is a superconductor below TC = 1.85 K and 
 HC2 = 2.2 T\, and develops antiferroquadrupolar\n(AFQ) order in magnetic f
 ields between  4 T and 14 T. The hyperfine constant of Pr is relatively la
 rge at\n52 mK and the Pr crystal electric field levels are closely involve
 d in both the superconducting and AFQ\nphases.\nTo explore the influence o
 f hyperfine interactions on the low temperature behaviour of PrOs4Sb12\, w
 e\nperformed magnetic susceptibility measurements as a function of tempera
 ture and magnetic field\, to\ntemperatures as low as 1 mK. We find that th
 e phase boundaries in this material anomalously develop\ndown to ~5 mK. AF
 Q order is enhanced at low temperature\, whereas superconductivity is supp
 ressed.\nWe explain our results in terms of a ground state composed of hyb
 rid nuclear-electronic states with novel\nlow energy excitations: the low 
 temperature quadrupole excitations that develop from these nuclear-\nelect
 ronic states\, are considerably modified compared to their higher temperat
 ure counterparts. I will\ndiscuss how this leads to a novel type of nuclea
 r-electronic quantum critical point at the AFQ transition\,\nwith a strong
 ly damped region of criticality. I will also explain how the hyperfine-ind
 uced suppression of\nsuperconductivity gives insight into a highly unconve
 ntional superconducting pairing mechanism.
LOCATION:Mott Seminar Room (531)\, Cavendish Laboratory\, Department of Ph
 ysics
END:VEVENT
END:VCALENDAR