Quantum Critical Quasiparticle Scattering within the Superconducting State of CeCoIn sub(5)

• Published in: Physical review letters 2016-07, Vol.117 (1)
• Main Authors: Paglione, Johnpierre, Tanatar, Ma, Reid, J-Ph, Shakeripour, H, Petrovic, C, Taillefer, Louis
• Format: Article
• Language: English
• Subjects: Evolution; Fluctuation; Magnetic fields; Scattering; Strength; Superconductivity; Thermal conductivity; Transport
• ISSN: 0031-9007; 1079-7114
• DOI: 10.1103/PhysRevLett.117.016601

The thermal conductivity [kappa] of the heavy-fermion metal CeCoIn sub(5) was measured in the normal and superconducting states as a function of temperature T and magnetic field H, for a current and field parallel to the [100] direction. Inside the superconducting state, when the field is lower than the upper critical field H sub()c2 [kappa]/T is found to increase as T[arrowright] 0, just as in a metal and in contrast to the behavior of all known superconductors. This is due to unpaired electrons on part of the Fermi surface, which dominate the transport above a certain field. The evolution of [kappa]/T with field reveals that the electron-electron scattering (or transport mass m*) of those unpaired electrons diverges as H[arrowright]H sub() c2from below, in the same way that it does in the normal state as H[arrowright]H sub() c2from above. This shows that the unpaired electrons sense the proximity of the field-tuned quantum critical point of CeCoIn5 at H*=H c2 even from inside the superconducting state. The fact that the quantum critical scattering of the unpaired electrons is much weaker than the average scattering of all electrons in the normal state reveals a k-space correlation between the strength of pairing and the strength of scattering, pointing to a common mechanism, presumably antiferromagnetic fluctuations.