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arXiv · 0809.0770

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

A. Harada·H. Mukuda·Y. Kitaoka·A. Thamizhavel·Y. Okuda·R. Settai·Y. Onuki·K. M. Itoh·E. E. Haller·H. Harima
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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 $T_{\rm N}$ exhibits its maximum at 8.5 K. The superconducting transition temperature $T_{\rm SC}$ has been found to be enhanced with increasing $T_{\rm N}$, before reaching the quantum critical point at which the AFM order collapses. Above $T_{\rm SC}$, 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.

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A. Harada, H. Mukuda, Y. Kitaoka, A. Thamizhavel, Y. Okuda, R. Settai, Y. Onuki, K. M. Itoh, E. E. Haller, H. Harima. 2008-09-04. Evolution of an Unconventional Superconducting State inside the Antiferromagnetic Phase of CeNiGe$_3$ under Pressure: a $^{73}$Ge-Nuclear-Quadrupole-Resonance Study. https://doi.org/10.1143/jpsj.77.103710

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