Coexistence of metallic and nonmetallic properties in the pyrochlore Lu${}_2$Rh${}_2$O${}_7$

Abstract

Transition metal oxides of the $4d$ and $5d$ block have recently become the targets of materials discovery, largely due to their strong spin-orbit coupling that can generate exotic magnetic and electronic states. Here we report the high pressure synthesis of Lu${}_2$Rh${}_2$O${}_7$, a new cubic pyrochlore oxide based on $4d^5$ Rh${}^{4+}$ and characterizations via thermodynamic, electrical transport, and muon spin relaxation measurements. Magnetic susceptibility measurements reveal a large temperature-independent Pauli paramagnetic contribution, while heat capacity shows an enhanced Sommerfeld coefficient, $\gamma$ = 21.8(1) mJ/mol-Rh K${}^2$. Muon spin relaxation measurements confirm that Lu${}_2$Rh${}_2$O${}_7$ remains paramagnetic down to 2 K. Taken in combination, these three measurements suggest that Lu${}_2$Rh${}_2$O${}_7$ is a correlated paramagnetic metal with a Wilson ratio of $R_W=2.5$. However, electric transport measurements present a striking contradiction as the resistivity of Lu${}_2$Rh${}_2$O${}_7$ is observed to monotonically increase with decreasing temperature, indicative of a nonmetallic state. Furthermore, although the magnitude of the resistivity is that of a semiconductor, the temperature dependence does not obey any conventional form. Thus, we propose that Lu${}_2$Rh${}_2$O${}_7$ may belong to the same novel class of non-Fermi liquids as the nonmetallic metal FeCrAs.

11 pages, 5 figures

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Cited by in corpus (4)

• Impact of iso-structural template layer on stabilizing pyrochlore Bi${}_2$Rh${}_2$O${}_7$
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• Emergent chiral symmetry in non-bipartite kagome and pyrochlore lattices with spin-orbit coupling
• Honeycomb lattice iridate on the verge of Mott-collapse