Evidence for chiral d-wave superconductivity in URu2Si2 from the field-angle variation of its specific heat

Abstract

Low-energy quasiparticle (QP) excitations in the heavy-fermion superconductor URu${}_2$Si${}_2$ were investigated by specific-heat $C(T,H,\varphi ,\theta )$ measurements of a high-quality single crystal. The occurrence of QP excitations due to the Doppler-shift effect was detected regardless of the field direction in $C(H)$ of the present clean sample, which is in sharp contrast to a previous report. Furthermore, the polar-angle-dependent $C(\theta )$ measured under a rotating magnetic field within the ac plane exhibits a shoulder-like anomaly at $\theta \sim 45$ deg and a sharp dip at $\theta =90$ deg ($H\parallel a$) in the moderate-field region. These features are supported by theoretical analyses based on microscopic calculations assuming the gap symmetry of $k_z(k_x+i{k}_y)$, whose gap structure is characterized by a combination of a horizontal line node at the equator and point nodes at the poles. The present results have settled the previous controversy over the gap structure of URu${}_2$Si${}_2$ and have authenticated its chiral $d$-wave superconductivity.

4 pages, 4 figures, published in J. Phys. Soc. Jpn

References in corpus (9)

• Rotational Symmetry Breaking in the Hidden-Order Phase of URu2Si2
• Exotic Superconducting Properties in the Electron-Hole Compensated Heavy Fermion `Semimetal' URu2Si2
• Emergent Rank-5 'Nematic' Order in URu2Si2
• Evidence for broken time-reversal symmetry in the superconducting phase of URu${}_2$Si${}_2$
• Orientational field-dependence of low-lying excitations in mixed state of unconventional superconductors
• Colossal thermomagnetic response in the exotic superconductor URu2Si2
• Direct observation of lattice symmetry breaking at the hidden-order transition in URu2Si2
• Cyclotron Resonance in the Hidden-Order Phase of URu2Si2
• Broken symmetries in URu2Si2

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