High Pressure NQR Measurement in CeCu_2Si_2 up to Sudden Disappearance of Superconductivity(Condensed matter: electronic structure and electrical, magnetic, and optical properties)

概要

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We report the results of ^<63>Cu nuclear quadrupole resonance (NQR) measurements on CeCu_2Si_2 under high pressures up to 4.8GPa. Enhanced spin fluctuations due to quantum criticality at ambient pressure are drastically suppressed with increasing pressure, whereas T_c increases from 0.7K at ambient pressure to 1.64K at 4.2GPa. We have found that bulk superconductivity suddenly disappears at 4.8GPa accompanied with a rapid decrease in the density of states at the Fermi level. The nuclear spin-lattice relaxation rate 1/T_1 at 4.2GPa reveals that anisotropic superconductivity in the strong-coupling regime is realized even under high pressure far from the antiferromagnetic critical point. Superconductivity under high pressure is unconventional in origin, but the spin fluctuation scenario is not likely to be applicable.
2008-12-15