Heavy Fermion Superconductivity in the Quadrupole Ordered State of PrV2Al20

TL;DR

This paper reports the discovery of heavy fermion superconductivity at 50 mK in PrV2Al20, a material with quadrupolar order, highlighting unconventional pairing driven by quadrupolar fluctuations.

Contribution

It demonstrates superconductivity in a quadrupole-ordered heavy fermion system, emphasizing the role of quadrupolar fluctuations in unconventional superconductivity.

Findings

Superconductivity at 50 mK in PrV2Al20 under ambient pressure.

Heavy fermion behavior with effective mass ~140.

Double transitions at 0.75 K and 0.65 K related to quadrupole and octapole orders.

Abstract

PrV$_2$Al$_{20}$ is a rare example of a heavy fermion system based on strong hybridization between conduction electrons and nonmagnetic quadrupolar moments of the cubic $\Gamma_3$ ground doublet. Here, we report that a high-quality single crystal of PrV$_2$Al$_{20}$ exhibits superconductivity at $T_{\rm c}=$ 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 $\Delta C/T \sim 0.3$ J/mol K$^2$ and the effective mass $m^*/m_0 \sim 140$ estimated from the temperature dependence of the upper critical field. Furthermore, the high-quality single crystals exhibit double transitions at $T_{\rm Q}$ = 0.75 K and $T^{*}$ = 0.65 K associated with quadrupole and octapole degrees of freedom of the $\Gamma_3$ doublet. In the ordered state, the specific heat $C/T$ shows a $T^3$ dependence, indicating the gapless mode associated with the quadrupole and/or octapole order. The strong sensitivity to impurity of the superconductivity suggests unconventional character due to significant quadrupolar fluctuations.