Anomalous vortex state in UTe

Tokiwa, Yoshifumi  ; Opletal, P.  ; Sakai, Hironori   ; Yamamoto, Etsuji  ; Kambe, Shinsaku  ; Tokunaga, Yo  ; Haga, Yoshinori   ; Kimata, Motoi*; Awaji, Satoshi*; Sasaki, Takahiko*; Yanase, Yoichi*

In unconventional superconductors, there are cases of vortex liquid-like state. When the pinning is strong, vortices do not move, and thus, the formation of such abnormal states requires pure and pristine crystals. Recently, the growth of pure single crystals of the spin-triplet superconductor UTe using a molten salt flux has been reported. In this study, we report research on vortices in UTe using such pure single crystals. As a result, in the magnetic field range of 15 T to 22 T, the critical current showed a maximum in temperature dependence, and a low-temperature region with a low critical current was observed deep in the superconducting state. This low critical current region matches the recently reported intermediate field superconducting phase. This suggests a weakening of the pinning force and a decrease in the critical current in the intermediate field superconducting phase.