Bulk evidence for a time reversal symmetry broken superconducting state in URu2Si2

G. Li; Q. Zhang; D. Rhodes; B. Zheng; P. Goswami; R. E. Baumbach; P. H. Tobash; F. Ronning; J. D. Thompson; E. D. Bauer; L. Balicas

doi:10.1103/PhysRevB.88.134517

paper

Bulk evidence for a time reversal symmetry broken superconducting state in URu2Si2

arXiv:1309.7671 · doi:10.1103/PhysRevB.88.134517

Abstract

URu $_{2}$ Si $_{2}$ is claimed to be a chiral \emph{d}-wave superconductor with a $k_{z} (k_{x} \pm i k_{y})$ time-reversal symmetry broken orbital component for the Cooper pair wave-function, which contains both nodal points and lines of nodes \cite{kasahara, kasahara2}. To study the magnetic response of such an unconventional state through a bulk, thermodynamic probe, we measured the magnetic torque $τ$ in very high-quality, well-characterized URu $_{2}$ Si $_{2}$ single-crystals \cite{altarawneh,altarawneh2} at high magnetic-fields $H$ and at very low temperatures $T$ . The magnetization $M (H) \propto τ (H) / H$ of URu $_{2}$ Si $_{2}$ , in its superconducting state and for angles within $1 5^{\circ}$ from the \emph{ab}-plane, reveals a change in its sign for $H$ approaching $H_{c 2}$ : from a clear diamagnetic response dominated by the pinning of vortices to a state with a smaller but "paramagnetic-like" hysteretic response which \emph{disappears} at $H_{c 2}$ , thus implying that it is intrinsically related to the superconducting state. We argue that this anomalous, angular-dependent behavior is evidence for a time-reversal symmetry broken superconducting state in URu $_{2}$ Si $_{2}$ , although not necessarily for the $k_{z} (k_{x} \pm i k_{y})$ state.

7 pages, 5 figures

Bulk evidence for a time reversal symmetry broken superconducting state in URu2Si2

Abstract

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