NMR studies on heavy fermion and conventional metal superlattices CeCoIn5/YbCoIn5

T Yamanaka,T Shibauchi,K Ishida,H Shishido,R Endo,Y Matsuda,Y Mizukami,T Terashima,M Shimozawa

doi:10.1088/1742-6596/807/1/012004

Abstract

We performed nuclear magnetic resonance (NMR) experiments on heavy fermion and conventional metal superlattices CeCoIn5/YbCoIn5. We succeeded in identifying the signals arising from CeCoIn5 and YbCoIn5 block layers (BLs) by comparing the spectra of the CeCoIn5/YbCoIn5 superlattices, CeCoIn5 thin film, and YbCoIn5 thin film. Furthermore, we found that the signals of Ce-BLs could be divided into signals arising from interfacial layers and inner layers even in one Ce-BL by comparing the spectra of two CeCoIn5/YbCoIn5 superlattices with different thickness of the Ce-BLs. A comparison of the spectra of the superlattices with different Ce-BL thickness and field dependence of nuclear-spin lattice relaxation rate 1/T1 indicate that antiferromagnetic spin fluctuations at the interfacial site are more suppressed than those at the inner layer site even in the Ce-BLs.

Highlights

The physics of strongly correlated electron systems is remarkably rich, and in such materials the entanglement of charge, spin, and orbital degrees of freedom often causes the emergence of exotic quantum phases
CeCoIn5 /YbCoIn5 superlattices, in which we found that the 1/T1 T of Ce-block layers (BLs) was suppressed with decreasing Ce-BL thickness, whereas that of Yb-BLs essentially the same as YbCoIn5 thin film[21]
nuclear magnetic resonance (NMR) information, i.e. spectroscopic information resolved for the Ce- and Yb-BLs separately

Summary

Introduction

The physics of strongly correlated electron systems is remarkably rich, and in such materials the entanglement of charge, spin, and orbital degrees of freedom often causes the emergence of exotic quantum phases. The technique of fabricating epitaxial superlattices consisting of heavy-fermion compounds and conventional metals has been developed and provides us a unique research field to study the interplay between locally inversion symmetry breaking and the heavyfermion characters[7, 8, 9]. Ordering[15, 16] and CeCoIn5 is considered to be located at the vicinity of AFM quantum critical point. In CeCoIn5 /YbCoIn5 superlattices, highly unusual superconducting properties such as the enhanced anisotropy of the upper critical field Hc2 [8] and anomalous enhancement of Hc2 regardless of Tc decrease have been observed[19, 20], in particular when the thickness of the. We discuss the NMR-spectrum difference in different Ce-BL thickness and show that the NMR spectra of Ce-BLs in CeCoIn5 /YbCoIn5 superlattices can be divided into the signals arising from interfacial and inner layers

Experimental

Results and discussions

Conclusion