Superconductivity in CeCoIn5-xSnx: Veil Over an Ordered State or Novel Quantum Critical Point?

TL;DR

This study investigates how Sn substitution in CeCoIn5 influences its quantum critical behavior, revealing a novel quantum critical point near the upper critical field H_{c2} linked to unconventional superconductivity.

Contribution

It provides evidence that the quantum critical point in CeCoIn5-xSnx is a distinct phenomenon associated with unconventional superconductivity, not just a coincidence with H_{c2}.

Findings

Quantum criticality observed at H_{c2} for x<0.12.

Non-Fermi liquid behavior evidenced by -ln(T) divergence.

Data aligns with spin-fluctuation theory.

Abstract

Measurements of specific heat and electrical resistivity in magnetic fields up to 9 T along [001] and temperatures down to 50 mK of Sn-substituted CeCoIn5 are reported. The maximal -ln(T) divergence of the specific heat at the upper critical field H_{c2} down to the lowest temperature characteristic of non-Fermi liquid systems at the quantum critical point (QCP), the universal scaling of the Sommerfeld coefficient, and agreement of the data with spin-fluctuation theory, provide strong evidence for quantum criticality at H_{c2} for all x < 0.12 in CeCoIn5-xSnx. These results indicate the "accidental" coincidence of the QCP located near H_{c2} in pure CeCoIn5, in actuality, constitute a novel quantum critical point associated with unconventional superconductivity.