Unconventional Superconductivity in Heavy Fermions

 

Dr. Filip Ronning

Los Alamos National Laboratory, USA

 

Cubic CeIn3 is an antiferromagnet at 10K. Superconductivity emerges under

pressure after suppression of magnetism with a maximum Tc of 0.2K. CeMIn5

(M=Co, Rh, Ir) is a quasi-2D variant of CeIn3 which results in an order of

magnitude increase in Tc. Unconventional superconductivity similar to

cuprates and Fe-based superconductors has been established with a gap

structure with dx2-y2 symmetry. Impurities are known to be a microscopic

probe of strongly correlated materials. We report a globally reversible

effect of electronic tuning on the magnetic phase diagram in CeCoIn5 driven

by electron (Pt and Sn) and hole (Cd, Hg) doping. We find that these

nominally non-magnetic dopants have a remarkably weak pair breaking effect

for a d-wave superconductor. As in the cuprates, the pair breaking is weaker

for hole dopants which induce magnetic moment than for electron dopants.

Furthermore, both Pt and Sn doping have a similar effect on

superconductivity despite being on different dopant sites, argueing against

the notion that superconductivity lives predominantly in the CeIn3 planes of

these materials. Finally, we shed qualitatively understanding on our results

with density functional theory calculations.