Superconducting Gap Structure of Single Crystals Organic Superconductor lambda-(BETS)2GaCl4 Studied by µSR

The quasi-2-dimensional organic superconductor lambda-(BETS)2GaCl4 is one of the key materials in strongly correlated systems because of the distinct geometrical structure of electron-electron correlation effect in the molecular conducting plane. The TF-muSR measurements have been done in ~130 mg aligned crystals in the perpendicular field configuration in order to determine the temperature dependence of superfluid density. The analyses intriguingly show that superconducting (SC) gap has steeper nodes structure than that of d-wave nodes by factor ~3. A decomposition of SC gap is necessary in order to reveal the SC gap structure in this system which can be described by a mixture of multi-gap symmetries. Thus, we propose to measure systematic TF-muSR measurements in other two magnetic field directions, along with the other two crystal axes, by preparing a different aligned crystals setup.