Akito Sakai

Heavy-fermion superconductivity in the quadrupole ordered state of PrV2Al20.

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.

Superconductivity in the Ferroquadrupolar State in the Quadrupolar Kondo Lattice PrTi2Al20

The cubic compound PrTi 2 Al 20 is a quadrupolar Kondo lattice system that exhibits quadrupolar ordering due to the non-Kramers Γ 3 ground doublet and has strong hybridization between 4 f and conduction electrons. Our study using high-purity single crystals reveals that PrTi 2 Al 20 exhibits type-II superconductivity at T c = 200 mK in the nonmagnetic ferroquadrupolar state. The superconducting critical temperature and field phase diagram indicates clean limit superconductivity with moderately enhanced effective mass of m * / m 0 ∼16.

Ferroquadrupolar ordering in PrTi 2 Al 20

The origin of the nonmagnetic phase transition in PrTi

Strong valence fluctuation effects in SmTr2Al20(Tr=Ti, V, Cr)

{}_{2}

Kondo resonance in PrTi2Al20: Photoemission spectroscopy and single-impurity Anderson model calculations

Al

Entropy Evolution in the Magnetic Phases of Partially Frustrated CePdAl

{}_{20}

µSR Evidence of Nonmagnetic Order and 141Pr Hyperfine-Enhanced Nuclear Magnetism in the Cubic Γ3 Ground Doublet System PrTi2Al20

, reported earlier in a macroscopic study, has been asserted microscopically using elastic and inelastic neutron scattering techniques. It has been shown spectroscopically that the crystalline-electric-field ground state is a nonmagnetic

Superconducting gap structure of CeIrIn 5 from field-angle-resolved measurements of its specific heat

{\ensuremath{\Gamma}}_{3}

Anomalous Enhancement of Seebeck Coefficient in Pr-Based 1-2-20 System with Non-Kramers Doublet Ground States

doublet, whereas the excited states are two triplets (

CePdAl - A Kondo lattice with partial frustration

{\ensuremath{\Gamma}}_{4}