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Recently, a nematic signature, i.e. a sudden resistivity anisotropy above a critical field B^* = 28 T, has been observed in CeRhIn₅[1]. This heavy fermion antiferromagnet (T_N = 3.85 K) superconducts under pressure above p_c = 23 kbar, associated with an antiferromagnetic quantum critical point (QCP). The reported nematic behavior survives at ambient pressure only until magnetic order is suppressed at a critical field of B_c =51 T, associated with a second QCP[2,3]. An open question is if and how the two QCPs, B-induced nematicity and p-induced superconductivity (SC) are related.
Here we report high-field (up to 65 T) / high-pressure (up to 40 kbar) studies of magnetotransport in CeRhIn₅. The combination of plastic diamond-anvil-cells, pulsed magnets, and focused-ion-beam microstructures enabled us to investigate this region in the (p,T,B) phase diagram. We show that nematicity and SC reside in distinct regions. Our experiments reveal a surprising enhancement of magnetic order in high fields with pressure.
[1] Ronning, F. et al., Nature 548, 313 (2017) [2] Jiao L. et al., PNAS 112, 673 (2015) [3] Rosa, P.F.S. et al., arxiv:1803.01748 (2018)