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تسجيل مستخدم جديدInfluence of internal disorder on the superconducting state in the organic layered superconductor kappa-(BEDT-TTF)2Cu[N(CN)2]Br
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We report high-sensitivity AC susceptibility measurements of the penetration depth in the Meissner state of the layered organic superconductor kappa-(BEDT-TTF)2Cu[N(CN)2]Br. We have studied nominally pure single crystals from the two different syntheses and employed controlled cooling procedures in order to minimize intrinsic remnant disorder at low temperatures associated with the glass transition, caused by ordering of the ethylene moieties in BEDT-TTF molecule at T_G = 75 K. We find that the optimal cooling procedures (slow cooling of -0.2 K/h or annealing for 3 days in the region of T_G) needed to establish the ground state, depend critically on the sample origin indicating different relaxation times of terminal ethylene groups. We show that, in the ground state, the behavior observed for nominally pure single crystals from both syntheses is consistent with unconventional d-wave order parameter. The in-plane penetration depth lambda_in(T) is strongly linear, whereas the out-of-plane component lambda_out(T) varies as T^2. In contrast, the behavior of single crystals with long relaxation times observed after slow (-0.2 K/h) cooling is as expected for a d-wave superconductor with impurities (i.e. lambda_in(T) propto lambda_out(T) propto T^2) or might be also reasonably well described by the s-wave model. Our results might reconcile the contradictory findings previously reported by different authors.
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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 sa
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The effect of disorder on the electronic properties near the Mott transition is studied in an organic superconductor $kappa$-(BEDT-TTF)$_{2}$Cu[N(CN)$_{2}$]Br, which is systematically irradiated by X-ray. We observe that X-ray irradiation causes Ande
rson-type electron localization due to molecular disorder. The resistivity at low temperatures demonstrates variable range hopping conduction with Coulomb interaction. The experimental results show clearly that the electron localization by disorder is enhanced by the Coulomb interaction near the Mott transition.
The magnetic field effect on the phase diagram of the organic Mott system $kappa$-(BEDT-TTF)$_{2}$Cu[N(CN)$_{2}$]Br in which the bandwidth was tuned by the substitution of deuterated molecules was studied by means of the resistivity measurements perf
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Static susceptibility of kappa-[(BEDT-TTF)1-x(BEDSe-TTF)x]2Cu[N(CN)2]Br alloys with the BEDSe-TTF content near the border-line of ambient pressure superconductivity (x~0.3) has been measured as a function of temperature, magnetic field, and pressure.
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