Tsujimoto Masaki, Matsumoto Yosuke, Tomita Takahiro, Sakai Akito, Nakatsuji Satoru
Institute for Solid State Physics, University of Tokyo, Kashiwa, Chiba 277-8581, Japan.
Institute for Solid State Physics, University of Tokyo, Kashiwa, Chiba 277-8581, Japan and PRESTO, Japan Science and Technology Agency (JST), 4-1-8 Honcho Kawaguchi, Saitama 332-0012, Japan.
Phys Rev Lett. 2014 Dec 31;113(26):267001. doi: 10.1103/PhysRevLett.113.267001. Epub 2014 Dec 23.
PrV2Al20 is a rare example of a heavy-fermion system based on strong hybridization between conduction electrons and nonmagnetic quadrupolar moments of the cubic Γ3 ground doublet. Here, we report that a high-quality single crystal of PrV2Al20 exhibits superconductivity at Tc=50 mK in the antiferroquadrupole-ordered state under ambient pressure. The heavy-fermion character of the superconductivity is evident from the specific heat jump of ΔC/T∼0.3 J/mol K(2) and the effective mass m*/m0∼140 estimated from the temperature dependence of the upper critical field. Furthermore, the high-quality single crystals exhibit double transitions at TQ=0.75 K and T*=0.65 K associated with quadrupole and octupole degrees of freedom of the Γ3 doublet. In the ordered state, the specific heat C/T shows a T(3) dependence, indicating the gapless mode associated with the quadrupole order, the octupole order, or both. The strong sensitivity to impurity of the superconductivity suggests unconventional character due to significant quadrupolar fluctuations.
PrV₂Al₂₀是基于传导电子与立方Γ₃基态双重态的非磁性四极矩之间强杂化的重费米子体系的一个罕见例子。在此，我们报道高质量的PrV₂Al₂₀单晶在常压下的反铁四极有序态中于Tc = 50 mK时表现出超导性。超导性的重费米子特性从ΔC/T ∼ 0.3 J/mol K²的比热跃变以及根据上临界场的温度依赖性估算出的有效质量m*/m₀ ∼ 140中可见一斑。此外，高质量单晶在TQ = 0.75 K和T* = 0.65 K处表现出与Γ₃双重态的四极和八极自由度相关的双转变。在有序态中，比热C/T呈现T³依赖性，表明与四极序、八极序或两者相关的无隙模式。超导性对杂质的强敏感性表明由于显著的四极涨落而具有非传统特性。
