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SUMMARY:Exploring the ordered states of the multi-phase superconductor CeR
 h2As2 - Dr. Konstantin Semeniuk\, MPI-CPfS Dresden/Germany
DTSTART:20240603T101500Z
DTEND:20240603T113000Z
UID:TALK217450@talks.cam.ac.uk
CONTACT:Malte Grosche
DESCRIPTION:The Kondo-lattice compound CeRh2As2 exhibits an extremely rare
  case of hosting multiple distinct superconducting (SC) states at a fixed 
 pressure or doping. The SC phase SC1 sets in at the critical temperature T
 c ≈ 0.3 K. Applying magnetic field of µ0 H=4 T along the c axis of th
 e tetragonal unit cell triggers a transition into the high-field phase SC2
 \, the upper critical field of which reaches 15 T [1]. The states SC1 an
 d SC2 have been proposed to have\, respectively\, even and odd parity of t
 he SC order parameter [2]. In the absence of magnetic field\, the superco
 nductivity is preceded by another ordered state “Phase I” [3\,4]. The
  microscopic nature of Phase I is currently unknown\, with magnetic and q
 uadrupolar orders proposed as candidates.\nThe uniqueness of the SC proper
 ties of CeRh2As2 has been partially attributed to its atypical crystalline
  structure\, with Ce atoms located in locally non-centrosymmetric environm
 ents\, while the unit cell has an overall inversion symmetry. Another impo
 rtant ingredient is the exceptionally strong electronic correlations. Toge
 ther with a pronounced non-Fermi-liquid behaviour\, these signal a proximi
 ty to a quantum critical point (QCP).\nRecently\, we explored the interpla
 y and relative stability of the ordered states of CeRh2As2 by tuning the m
 aterial with hydrostatic pressure. We revealed a quantum critical point (Q
 CP) of Phase I at P0 = 0.5 GPa\, which is the source of pairing mediatin
 g fluctuations and extremely high quasiparticle masses. We also observed a
  remarkably rapid suppression of the SC phase switching field H* with pres
 sure\, with the putative odd-parity SC2 phase becoming the dominant SC sta
 te. We discuss this result in the context of the even-odd parity model.\n\
 n\n[1] S. Khim & J. Landaeta et al.\, Science\, 373 (2021) 1012–1016.\n\
 n[2] J. Landaeta et al.\, Phys. Rev .X\, 12 (2022) 031001.\n\n[3] D. Hafne
 r et al.\, Phys. Rev. X\, 12 (2022) 011023.\n\n[4] K. Semeniuk et al.\, Ph
 ys. Rev. B\, 107 (2023) L220504.\n
LOCATION:Mott Seminar Room (531)\, Cavendish Laboratory\, Department of Ph
 ysics
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