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arXiv · 2406.16575

Coexistence of local magnetism and superconductivity in the heavy-fermion CeRh$_2$As$_2$ revealed by $\mu$SR studies

Seunghyun Khim·Oliver Stockert·Manuel Brando·Christoph Geibel·Chirstopher Baines·Thomas J. Hicken·Hubertus Luetkens·Debarchan Das·Toni Shiroka·Zurab Guguchia·Robert Scheuermann
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Abstract

The superconducting (SC) state ($T_\mathrm{c}$ = 0.3 K) of the heavy-fermion compound CeRh$_2$As$_2$, which undergoes an unusual field-induced transition to another high-field SC state, emerges from an unknown ordered state below $T_\mathrm{o}$ = 0.55 K. While an electronic multipolar order of itinerant Ce-4$f$ states was proposed to account for the $T_\mathrm{o}$ phase, the exact order parameter has not been known to date. Here, we report on muon spin relaxation ($\mu$SR) studies of the magnetic and SC properties in CeRh$_2$As$_2$ single crystals at low temperatures. We reveal a magnetic origin of the $T_\mathrm{o}$ order by identifying a spontaneous internal field below $T_\mathrm{o}$ = 0.55 K. Furthermore, we find evidence of a microscopic coexistence of local magnetism with bulk superconductivity. Our findings open the possibility that the $T_\mathrm{o}$ phase involves both dipole and higher order Ce-4$f$ moment degrees of freedom and accounts for the unusual non-Fermi liquid behavior.

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Seunghyun Khim, Oliver Stockert, Manuel Brando, Christoph Geibel, Chirstopher Baines, Thomas J. Hicken, Hubertus Luetkens, Debarchan Das, Toni Shiroka, Zurab Guguchia, Robert Scheuermann. 2024-06-24. Coexistence of local magnetism and superconductivity in the heavy-fermion CeRh$_2$As$_2$ revealed by $\mu$SR studies. https://doi.org/10.1103/physrevb.111.115134

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