Possible Fulde–Ferrell–Larkin–Ovchinnikov superconducting state in [formula omitted]: New evidence from pressure studies

Abstract

The heavy-fermion superconductor (SC) CeCoIn 5 shows an anomaly in specific heat, inside the SC state, at low temperatures and close to the upper critical field ( B c 2 ) . This feature was attributed to a phase transition from the classical vortex state into a Fulde–Ferrell–Larkin–Ovchinnikov phase. Intriguingly, at ambient pressure, CeCoIn 5 is situated close to an antiferromagnetic quantum critical point (QCP) and underlying magnetic fluctuations may be responsible for the specific heat feature. By applying pressure, the system is driven away from the QCP. We present first results of a specific heat study under hydrostatic pressure and in high magnetic fields as an attempt to clarify the origin of this phase.