Field induced multiple superconducting phases in UTe along hard magnetic axis

Sakai, Hironori   ; Tokiwa, Yoshifumi  ; Opletal, P.  ; Kimata, Motoi*; Awaji, Satoshi*; Sasaki, Takahiko*; Aoki, Dai*; Kambe, Shinsaku  ; Tokunaga, Yo  ; Haga, Yoshinori   

The superconducting (SC) phase diagram in uranium ditelluride is explored under magnetic fields () along the hard magnetic -axis using a high-quality single crystal with = 2.1 K. Simultaneous electrical resistivity and AC magnetic susceptibility measurements discern low- and high-field SC (LFSC and HFSC, respectively) phases with contrasting field-angular dependence. Crystal quality increases the upper critical field of the LFSC phase, but the of T, at which the HFSC phase appears, is always the same through the various crystals. A phase boundary signature is also observed inside the LFSC phase near , indicating an intermediate SC phase characterized by small flux pinning forces.