Vortex phase diagram of the kagome superconductor CsV₃⁢Sb₅

The screening response of the kagome superconductor CsV₃⁢Sb₅ was obtained from high-resolution ac mutual inductance measurements. At zero applied magnetic field and low temperatures, we observe no evidence for gapless quasiparticles, while near T_c we find evidence for enhanced fluctuations. A rich vortex state appears above H_c⁢1≈30 Oe, exhibiting successive emergence of vortex phases. For a fixed magnetic field, lowering the temperature below T_c⁡(H) leads to a wide range of vortex liquid state in a landscape of weak pinning potential, which gives rise to an irreversibility line. Further lowering the temperature, we identify the vortex melting line followed by the peak effect manifested in enhanced vortex pinning strength and critical current. Finally, we suggest that such an unusual behavior, where the peak effect region is fully contained within the vortex lattice state below the irreversibility line, is a consequence of the strong anisotropy and weak bulk pinning in CsV₃⁢Sb₅.. Authors: Zhang, Xinyang [SLAC National Accelerator Laboratory (SLAC), Menlo Park, CA (United States). Stanford Institute for Materials and Energy Science (SIMES); Stanford Univ., CA (United States); SLAC] (ORCID:0000000173443644); Zic, Mark P. [Stanford Univ., CA (United States)]; Chen, Dong [Max Planck Institute for Chemical Physics of Solids, Dresden (Germany); Qingdao Univ. (China)] (ORCID:0000000271709725); Shekhar, Chandra [Max Planck Institute for Chemical Physics of Solids, Dresden (Germany)]; Felser, Claudia [Max Planck Institute for Chemical Physics of Solids, Dresden (Germany)]. DOE Contract: AC02-76SF00515. Subjects: 75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; Kagome lattice; flux pinning; magnetic techniques; magnetization measurements; resistivity measurements; superconductors; vortex lattices; vortices in superconductors