Thermal expansion of organic superconductor k-(D4-BEDT-TTF)2Cu{N(CN)2}Br. Isotopic effect

Abstract

Linear thermal expansion coefficient (LTEC) of single crystal k-(D4-BEDT-TTF)2Cu[N(CN)2]Br was studied across the crystal layers in the temperature range 2-290 K using the method of precise capacitive dilatometry. Below Tc = 11,6 K the LTEC of the sample had a small negative value, which is apparently due to the transition from the paramagnetic metal in the superconducting state. There was a bend of temperature dependence of the LTEC, which shows broad peak around 40 K and can be attributed to the elastic lattice anomaly around the end-point of Mott boundary. A sharp jump in the LTEC values and hysteresis was observed in the area of Tg ~ 75-77 K, what is likely explained by the transition in a glass-like state. The isotope effect in the thermal expansion is discusses, which manifested itself in a shift of the phase transitions in comparison with fully deuterated BEDT-TTF sample.

arXiv comment11 pages, 6 figures

References in corpus (5)

• Similarities between organic and cuprate superconductors
• Unconventional critical behaviour in a quasi-two-dimensional organic conductor
• 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
• Determining ethylene group disorder levels in $\kappa$-(BEDT-TTF)${}_2$Cu[N(CN)${}_2$]Br
• Origin of the glass-like dynamics in molecular metals $\kappa$-(BEDT-TTF)${}_{\text{2}}$X: implications from fluctuation spectroscopy and $\text{ab initio}$ calculations