Multipole and superconducting state in PrIr2Zn20probed by muon spin relaxation

Abstract

We performed muon spin rotation and relaxation (μSR) measurements in the caged-structure heavy-fermion system PrIr 2 Zn 20 to elucidate its magnetic and superconducting properties. Temperature-independent μSR spectra were observed below 1 K, indicating that the phase transition at 0.11 K is of a nonmagnetic origin, most probably pure quadrupole ordering. In the superconducting phase, no sign of unconventional superconductivity, such as superconductivity with broken time-reversal symmetry, was seen below T c = 0.05 K. We also observed spontaneous muon spin precession in zero field in the paramagnetic phase below 15 K, suggesting that unusual coupling between 141 Pr nuclei and muons is realized in PrIr 2 Zn 20 .

Quadrupole-driven non-Fermi-liquid and magnetic-field-induced heavy fermion states in a non-Kramers doublet system

“…1 (a) is the manifestation of the AFQ order. [27,32,33] As shown with the open triangles in the inset of Fig. 1 (b), upon applying magnetic field for B≥3 T, the peak , T /T (ρ) 0 < 3, C 4f and ∆ρ in magnetic fields better follow the calculation by using a two-channel Anderson lattice model [10] as shown with the (red) solid curves than the (blue) dotted curve calculated with the impurity quadrupole Kondo model [6] shifts to lower temperatures and disappears at B=4.5 T. The behavior of the specific heat peak at T Q in the magnetic fields is much different from the previous report where the peak is split into two for 1≤B≤3 T. [27] This inconsistency results from an extrinsic effect of another grain contained in the previous sample whose crystalline axis is directed away from the a-axis of the dominant crystal.…”

“…On the other hand, below T Q , a superconducting transition sets in at T c = 0.05 K, suggesting a possible interplay between the quadrupole fluctuations and the superconducting Cooper-pair formation. [27,[32][33][34] The coexistence of superconductivity with quadrupole order also manifests in isostructural compounds PrRh 2 Zn 20 , PrTi 2 Al 20 , and PrV 2 Al 20 . [35][36][37][38] In PrTi 2 Al 20 and PrV 2 Al 20 , the strong hybridization between the 4f elections and the conduction electrons was revealed by the Al-NMR and Pr 3d-4f resonant photoemission measurements.…”