title: Detection of an unconventional superconducting phase in the vicinity of the strong first-order magnetic transition in CrAs using (75)As-nuclear quadrupole resonance.
abstract: Pressure-induced superconductivity was recently discovered in the binary helimagnet CrAs. We report the results of measurements of nuclear quadrupole resonance for CrAs under pressure. In the vicinity of the critical pressure P(c) between the helimagnetic (HM) and paramagnetic (PM) phases, a phase separation is observed. The large internal field remaining in the phase-separated HM state indicates that the HM phase disappears through a strong first-order transition. This indicates the absence of a quantum critical point in CrAs; however, the nuclear spin-lattice relaxation rate 1/T(1) reveals that substantial magnetic fluctuations are present in the PM state. The absence of a coherence effect in 1/T(1) in the superconducting state provides evidence that CrAs is the first Cr-based unconventional superconductor.
authors.affiliation: Department of Physics, Kobe University, Kobe 657-8501, Japan.
authors.forename: Hisashi
authors.initials: H
authors.lastname: Kotegawa
authors.affiliation: Department of Physics, Kobe University, Kobe 657-8501, Japan.
authors.forename: Shingo
authors.initials: S
authors.lastname: Nakahara
authors.affiliation: Department of Physics, Kobe University, Kobe 657-8501, Japan.
authors.forename: Rui
authors.initials: R
authors.lastname: Akamatsu
authors.affiliation: Department of Physics, Kobe University, Kobe 657-8501, Japan.
authors.forename: Hideki
authors.initials: H
authors.lastname: Tou
authors.affiliation: Department of Physics, Kobe University, Kobe 657-8501, Japan.
authors.forename: Hitoshi
authors.initials: H
authors.lastname: Sugawara
authors.affiliation: Department of Physics, Kobe University, Kobe 657-8501, Japan.
authors.forename: Hisatomo
authors.initials: H
authors.lastname: Harima