Pressure-induced anomalous magnetism and unconventional superconductivity inCeRhIn5:115

Abstract

We report 115 In nuclear-quadrupole-resonance ͑NQR͒ measurements of the pressure( P)-induced superconductor CeRhIn 5 in the antiferromagnetic ͑AF͒ and superconducting ͑SC͒ states. In the AF region, the internal field H int at the In site is substantially reduced from H int ϭ1.75 kOe at Pϭ0 to 0.39 kOe at Pϭ1.23 GPa, while the Néel temperature slightly changes with increasing P. This suggests that either the size in the ordered moment M Q ( P) or the angle ( P) between the direction of M Q ( P) and the tetragonal c axis is extrapolated to zero at P*ϭ1.6Ϯ0.1 GPa at which a bulk SC transition is no longer emergent. In the SC state at P ϭ2.1 GPa, the nuclear spin-lattice relaxation rate 115 (1/T 1 ) has revealed a T 3 dependence without the coherence peak just below T c , giving evidence for the unconventional superconductivity. The dimensionality of the magnetic fluctuations in the normal state is also discussed.

Pressure-temperature phase diagram of antiferromagnetism and superconductivity inCeRhIn5andCeIn3

“…Thus, the bulk nature of the P -induced SC state in CeIn 3 has not been confirmed yet by other measurements than resistivity. This is in contrast with the case of CeRhIn 5 where the bulk nature of the SC phase was fully established [7] which continues up to 8 GPa [11].Here we report new P -T phase diagrams for CeRhIn 5 and CeIn 3 obtained through 115 In-T 1 measurements and present a possible explanation for the different P dependence of the SC phase in the two compounds.The single crystals of CeRhIn 5 and CeIn 3 were grown by the self-flux and Czochralski Method, respectively [4,12], and were moderately crushed into grains in or- …”

“…This P * is comparable to P c = 1.63 GPa at which the SC signature appears [4], which was indicative of a second-order like AF-to-SC transition rather than the first-order one suggested previously [4]. At P = 2.1 GPa, it was found that the nuclear spin-lattice relaxation rate 1/T 1 reveals a T 3 dependence below the SC transition temperature T c , which shows the existence of line-nodes in the gap function [7]. It is, however, not yet clear how the electronic states change with P when the AF phase evolves into the SC phase.…”

“…The superconductivity in these compounds, however, occurs only in extreme conditions where the pressure exceeds ∼ 2 GPa and temperature (T ) is cooled down below ∼ 1 K. Indeed the experiments were restricted mainly to transport measurements. The discovery of P -induced HF superconductors in Ce-based HF-AF compounds has stimulated further experimental works under P [4,5,6,7]. In order to gain profound insight into a relationship between magnetism and superconductivity in HF systems, systematic NMR/NQR experiments under P are important, since they can probe the evolution of the magnetic properties toward the onset of SC phase.…”

Non-Fermi Liquid Regimes and Superconductivity in the Low Temperature Phase Diagrams of Strongly Correlated d- and f-Electron Materials

“…Monthoux et al [134], however, emphasize that this kind of magnetically mediated superconductivity is sensitive to small changes in the band structure, possibly yielding an explanation why CeRhIn 5 with a c/a ratio intermediate between CeIrIn 5 and CeCoIn 5 only exhibits superconductivity below T c = 110 mK. For the entire series of CeT In 5 compounds, both the specific heat [135] and the spin-lattice relaxation rate divided by temperature 1/T 1 T , measured by means of NQR [136][137][138], provide compelling evidence for the existence of line nodes in the superconducting energy gap and therefore unconventional superconductivity.…”

Zero-field NMR and NQR measurements of the antiferromagnet URhIn5

“…[5][6][7] CeRhIn 5 , an antiferromagnet with Néel temperature T N = 3.8 K at ambient pressure, becomes superconducting near 2 K, with suppression of the antiferromagnetism, at applied pressure of P * ∼ 2 GPa. 8 Systematic nuclear magnetic resonance (NMR) investigations of the Ce115 systems have established that these superconductors have d-wave superconducting gaps, [9][10][11][12] and that antiferromagnetic (AFM) spin interactions play an active role in the superconducting pairing. [13][14][15][16] In the Pu115 systems, NMR measurements show d-wave-like superconducting gap behavior, 17,18 with T c 's an order of magnitude higher than those for the Ce115.…”