Evolution of an Unconventional Superconducting State inside the Antiferromagnetic Phase of CeNiGe${}_3$ under Pressure: a ${}^{73}$Ge-Nuclear-Quadrupole-Resonance Study

Abstract

We report a ${}^{73}$Ge nuclear-quadrupole-resonance (NQR) study on novel evolution of unconventional superconductivity in antiferromagnetic (AFM) CeNiGe${}_3$. The measurements of the ${}^{73}$Ge-NQR spectrum and the nuclear spin-lattice relaxation rate ($1/T_1$) have revealed that the unconventional superconductivity evolves inside a commensurate AFM phase around the pressure ($P$) where Néel temperature $T_{\mathrm{N}}$ exhibits its maximum at 8.5 K. The superconducting transition temperature $T_{\mathrm{SC}}$ has been found to be enhanced with increasing $T_{\mathrm{N}}$, before reaching the quantum critical point at which the AFM order collapses. Above $T_{\mathrm{SC}}$, the AFM structure transits from an incommensurate spin-density-wave order to a commensurate AFM order at $T\sim 2$ K, accompanied by a longitudinal spin-density fluctuation. With regard to heavy-fermion compounds, these novel phenomena have hitherto never been reported in the $P$-$T$ phase diagram.

4 pages, 5 figures

References in corpus (1)

• Evidence for ferromagnetic spin-pairing superconductivity in UGe${}_2$: A ${}^{73}$Ge-NQR study under pressure

Cited by in corpus (1)

• Novel phase diagram for antiferromagnetism and superconductivity in pressure-induced heavy-fermion superconductor Ce${}_2$RhIn${}_8$ probed by In-NQR