Impurity Effect on the In-plane Penetration Depth of the Organic Superconductors $\kappa$-(BEDT-TTF)${}_{2}X$ ($X$ = Cu(NCS)${}_2$ and Cu[N(CN)${}_2$]Br)

Abstract

We report the in-plane penetration depth ${\lambda }_{\parallel }$ of single crystals $\kappa$-(BEDT-TTF)${}_{2}X$ ($X=$ Cu(NCS)${}_2$ and Cu[N(CN)${}_2$]Br) by means of the reversible magnetization measurements under the control of cooling-rate. In $X$ = Cu(NCS)${}_2$, ${\lambda }_{\parallel }(0)$ as an extrapolation toward $T$ = 0 K does not change by the cooling-rate within the experimental accuracy, while $T_{\text{c}}$ is slightly reduced. On the other hand, in $X$ = Cu[N(CN)${}_2$]Br, ${\lambda }_{\parallel }(0)$ indicates a distinct increase by cooling faster. The different behavior of ${\lambda }_{\parallel }(0)$ on cooling-rate between the two salts is quantitatively explained in terms of the local-clean approximation (London model), considering that the former salt belongs to the very clean system and the later the moderate clean one. The good agreement with this model demonstrates that disorders of ethylene-group in BEDT-TTF introduced by cooling faster increase the electron(quasiparticle)-scattering, resulting in shorter mean free path.

arXiv comment8 pages, 9 figures

References in corpus (6)

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• Determining ethylene group disorder levels in $\kappa$-(BEDT-TTF)${}_2$Cu[N(CN)${}_2$]Br
• In-plane superfluid density and microwave conductivity of the organic superconductor κ-(BEDT-TTF)2Cu[N(CN)2]Br: evidence for d-wave pairing and resilient quasiparticles
• Superconductor-Insulator Phase Separation Induced by Rapid Cooling in kappa-(ET)_2Cu[N(CN)_2]Br
• Effects of Disorder on the Pressure-Induced Mott Transition in $\kappa$-BEDT-TTF)${}_2$Cu[N(CN)${}_2$]Cl
• Phase separation in the vicinity of the surface of $\kappa$-(BEDT-TTF)${}_2$Cu[N(CN)${}_2$]Br by fast cooling
• Suppression of superconductivity by non-magnetic disorder in organic superconductor $\kappa$-(BEDT-TTF)${}_2$Cu(NCS)${}_2$
• Inhomogeneous superconductivity in organic conductors: role of disorder and magnetic field
• Pseudogap formation in organic superconductors
• Theory of Electron Transport near Anderson-Mott Transitions
• Fate of the Hebel-Slichter peak in superconductors with strong antiferromagnetic fluctuations
• Impurity Effect on Superconducting Properties in Molecular Substituted Organic Superconductor $\kappa$-(ET)${}_2$Cu(NCS)${}_2$
• Superconductivity and fluctuating magnetism in quasi two-dimensional kappa-(BEDT-TTF)2Cu[N(CN)2]Br probed with implanted muons