Coexistence of metallic and nonmetallic properties in the pyrochlore Lu2Rh2O7

• Published in: npj quantum materials Vol. 4; no. 1
• Main Authors: Hallas, Alannah M., Sharma, Arzoo Z., Mauws, Cole, Chen, Qiang, Zhou, Haidong D., Ding, Cui, Gong, Zizhou, Tachibana, Makoto, Sarte, Paul M., Attfield, J. Paul, Luke, Graeme M., Wiebe, Christopher R.
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group 01.03.2019
• Subjects: Electrical resistivity; Electron states; Fermi liquids; Magnetic induction; Magnetic permeability; Muon spin relaxation; Muons; Spin-orbit interactions; Temperature dependence; Transition metal oxides; Transport
• ISSN: 2397-4648; 2397-4648
• DOI: 10.1038/s41535-019-0148-1

Abstract Transition metal oxides of the 4 d and 5 d 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 4 d 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, γ  = 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.