Competition between magnetism and superconductivity in the organic metal $\kappa$-[BEDT-TTF]${}_2$Cu[N(CN)${}_2$]Br

Abstract

Ultrasonic velocity and attenuation measurements on the quasi-two-dimensional organic conductor $\kappa$-[BEDT-TTF]${}_2$Cu[N(CN)${}_2$]Br give the first determination of the coexistence zone of the antiferromagnetic and superconducting phases which extends deep in the metallic part of the pressure-temperature phase diagram of these salts. This zone is identified from a precise control of the ordering in ethylene end groups which acts as an internal pressure. The two phases are found to compete whereas superconducting fluctuations begin to contribute to the attenuation at 15 K, namely at the onset of magnetic order that is well above the superconducting transition temperature $T_c$ = 11.9 K. Finally, the temperature profile of sound attenuation for both longitudinal and transverse phonon polarizations is found to be inconsistent with a conventional \textit{s}-wave order parameter.

References in corpus (12)

• Mott transition, antiferromagnetism, and unconventional superconductivity in layered organic superconductors
• Unconventional critical behaviour in a quasi-two-dimensional organic conductor
• Mott transition and transport crossovers in the organic compound $\kappa -(BEDT-TTF{)}_{2}Cu[N(CN{)}_2]Cl$
• Evidence for structural and electronic instabilities at intermediate temperatures in $\kappa$-(BEDT-TTF)${}_2$X for X=Cu[N(CN)${}_2$]Cl, Cu[N(CN)${}_2$]Br and Cu(NCS)${}_2$: Implications for the phase diagram of these quasi-2D organic superconductors
• Mott Transition, Compressibility Divergence and P-T Phase Diagram of Layered Organic Superconductors: An Ultrasonic Investigation
• Imaging phase separation near the Mott boundary in the correlated organic superconductors $\kappa$-(BEDT-TTF)${}_2$X
• Elastic Study of Antiferromagnetic Fluctuations in the Layered Organic Superconductors kappa-(BEDT-TTF)_2X
• Influence of internal disorder on the superconducting state in the organic layered superconductor kappa-(BEDT-TTF)2Cu[N(CN)2]Br
• Determining ethylene group disorder levels in $\kappa$-(BEDT-TTF)${}_2$Cu[N(CN)${}_2$]Br
• Substitution Effect by Deuterated Donors on Superconductivity in $\kappa$-(BEDT-TTF)${}_2$Cu[N(CN)${}_2$]Br
• Phase separation in the vicinity of the surface of $\kappa$-(BEDT-TTF)${}_2$Cu[N(CN)${}_2$]Br by fast cooling
• Superconducting fluctuation corrections to ultrasound attenuation in layered superconductors

Cited by in corpus (5)

• Molecular Quantum Materials: Electronic Phases and Charge Dynamics in Two-Dimensional Organic Solids
• Fulde-Ferrell-Larkin-Ovchinnikov state induced by antiferromagnetic order in $\kappa$-type organic conductors
• From charge- and spin-ordering to superconductivity in the organic charge-transfer solids
• Mixed pairing symmetry in κ-(BEDT-TTF)_2 X organic superconductors from ultrasonic velocity measurements
• Antiferromagnetic fluctuations in the quasi-two-dimensional organic superconductor detected by Raman spectroscopy