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UID:DSC-21564
DTSTART;TZID=Europe/Berlin:20241213T110000
SEQUENCE:1734072254
TRANSP:OPAQUE
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URL:https://dresden-science-calendar.de/calendar/en/detail/21564
LOCATION:IFW\, Helmholtzstraße 2001069 Dresden
SUMMARY:Cichorek: Vortex Penetration Into the Putative Chiral Superconducto
 r 4Hb TaS2 by Local Magnetization Measurements 
CLASS:PUBLIC
DESCRIPTION:Speaker: Tomasz Cichorek\nInstitute of Speaker: Institute of Lo
 w Temperature and Structure Research\, Polish Academy of Sciences\, 50-422
  Wroc&amp\;#322\;a\nTopics:\n\n Location:\n  Name: IFW (B3E.26\, IFW Dresd
 en)\n  Street: Helmholtzstraße 20\n  City: 01069 Dresden\n  Phone: \n  Fa
 x: \nDescription: Heterostructures formed by alternating magnetic and supe
 rconducting layers are predicted systems for the realization of exotic top
 ological quantum phases and resultant Majorana bound states. A promising r
 oute to realize topological superconductivity is related to a van der Waal
 s material 4Hb-TaS2 (a critical temperature Tc &amp\;amp\;#8771\; 2.7 K). 
 This naturally occurring heterostructure is composed of strongly correlate
 d phases with drastically different ground states [1]. In bulk form\, 2H-T
 aS2 is a conventional superconductor (Tc&amp\;amp\;#8201\;=&amp\;amp\;#820
 1\;0.7&amp\;amp\;#8201\;K)\, while 1T TaS2 is a Mott insulator and can hos
 t a quantum spin liquid. Chiral superconductivity in 4Hb-TaS2 is suggested
  from\, e.g.\, muon spin relaxation experiments that revealed a spontaneou
 s appearance of magnetic moments at T &amp\;amp\;#8804\; Tc [1]. Furthermo
 re\, an intriguing vortex memory effect [2]\, which has been observed slig
 htly above Tc\, is a topic of present debate whether topological order is 
 involved in vortex nucleation in the thermal cycling process.  Here we inv
 estigate vortex penetration into 4Hb Ta1.000(8)S1.97(4)Se0.017(2) samples 
 for a magnetic field H parallel to the layers stacking direction. Using mi
 cro-Hall-probe magnetometry\, we focus on the field of first flux penetrat
 ion and the resultant temperature dependence of the lower critical field H
 c1(T) as a function of sample thickness d. For thick samples (d &amp\;amp\
 ;#8771\; 180 mm)\, we observe an anomalous enhancement of Hc1 at 0.5Tc tha
 t consists of a non-saturating T-dependence down to 0.007 K being preceded
  by a concave curvature below 0.5 K. Above 1.5 K\, the Hc1(T) data show a 
 single-band isotropic s-wave behavior. A sharp anomaly in Hc1(T) far below
  Tc and no sign of saturation in the limit T = 0 suggest that the supercon
 ducting state of 4Hb-TaS2 is both multiband and multisymmetric. This scena
 rio is similar to that realized in the other putative chiral superconducto
 r PrOs4Sb12 (Tc &amp\;amp\;#8771\; 1.85 K) where multiband order parameter
 s are composed of a sign-changing smaller gap and a large isotropic s-wave
  gap [3]. However\, when the thickness is reduced\, the anomaly in Hc1(T) 
 of 4Hb-TaS2  is shifted toward lower temperatures and its magnitude substa
 ntially diminishes. For a thin sample (d &amp\;amp\;#8771\; 4 mm)\, the la
 ck of saturation is absent and the entire Hc1(T) dependence is well descri
 bed by the conventional relation derived from the Bardeen-Cooper-Schrieffe
 r theory. We emphasize that Tc  does not depend on d. Our findings are at 
 odds with the effect produced by the Bean-Livingston and geometric barrier
 s\, and thus point at the presence of unknown yet factor determining a vor
 tex penetration into the putative chiral superconductor 4Hb-TaS2.  Referen
 ces 1. A. Ribak et al.\, Sci. Adv. 6 eaax9480 (2020). 2. B. Persky\, et al
 .\, Nature 607\, 692 (2022). 3. J. Juraszek et al.\, Phys. Rev. Lett. 124\
 , 027001 (2020).
DTSTAMP:20261007T015230Z
CREATED:20241210T063846Z
LAST-MODIFIED:20241213T064414Z
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