Study of the isotopic effect and the influence of cooling rate on pining mechanism in organic superconductor κ-(BEDTTTF)2Cu[N(CN)2]Br

Abstract

This study investigates the impact of the cooling rate on pinning efficiency and vortex dynamics of the deuterated and hydrogenated organic superconductor κ-(BEDT-TTF)₂Cu[N(CN)₂]Br. It also examines the effect of magnetic field on the critical transition temperature and the isotopic effect. Slow cooling enhances pinning strength, while rapid cooling weakens pinning efficiency and shifts vortex regime transitions to lower magnetic fields, particularly in the deuterated compound. This suppression of vortex pinning by fast cooling is inconsistent with the simple pinning effect and can be explained by the ethylene-disorder-domain model. The dominant pinning mechanism is not significantly affected by the cooling rate in the hydrogenated compound, but is radically affected in deuterated one. The critical transition temperature decreases with the magnetic field, and the test of the isotopic effect confirms that the mechanism responsible for superconductivity is far from conventional in our compound, and reveals a weak isotope effect, suggesting that interlayer coupling plays a significant role in layered organic superconductors.