Schematic presentation of (left) the usual BCS pairing state with zero resulting momentum and spin and (right) the FFLO pairing state with a finite center-of-mass momentum, q. The circles represent the Fermi surfaces for spin-up and spin-down bands.
Temperature dependence of the specific-heat difference between the superconducting and normal state, ΔC/T, of κ-(BEDT-TTF)2Cu(NCS)2 in magnetic fields applied parallel to the superconducting layers.
(a) High-field data shown in Fig. 2 in an expanded scale. (b) Specific-heat data measured at 22 T during warming and cooling.
(a) Magnetic-torque data of κ-(BEDTTTF)2Cu(NCS)2 at various temperatures for in-plane magnetic fields. For T = 1.7 K, data for both up and down field sweeps, otherwise only down sweeps are shown. The vertical arrows mark the small dip-like features, which are associated with the transition into the FFLO state. (b) Schematic phase diagram deduced from the data shown in (a) and Fig. 2 . 18
(a) Temperature dependence of the specific heat of β″(BEDT-TTF)2SF5CH2CF2SO3 in a double-logarithmic scale. Data in the superconducting state in zero field and in the normal state at 10 T applied perpendicular to the BEDT-TTF planes are shown. The solid line is a fit to the 10 T data below 2 K using a linear and cubic term. (b) Temperature dependence of the specific-heat difference between the superconducting and normal state. The lines show the BCS behavior for weak coupling (dashed) 30 and moderately strong coupling (solid). 31 The inset shows the electronic part of the specific heat, Ce , divided by γTc as function of Tc /T. The solid line shows the exponential vanishing of Ce towards low T.
Difference between the specific heat for selected in-plane magnetic fields and the normal-state specific heat divided by temperature as a function of temperature for β″-(BEDT-TTF)2SF5CH2CF2SO3. The inset shows thefield-dependent evolution of the electronic part of the specific heat, Ce , divided by temperature.
Superconducting phase diagram of β″-(BEDTTTF)2SF5CH2CF2SO3 for fields aligned parallel to and by 0.23 and 0.31° out of the superconducting layers. The data of the second anomaly observed at 0.23° [Fig. 9b ] are labeled by T* (open blue triangles). The dashed line is a rough extrapolation of the data between 2 and 3 K to the Pauli limit of 9.73 T. The dotted line represents the calculated Hc 2 (see text for details). The inset shows the angular dependence of Tc and T* at 9.5 and 10 T.
Specific-heat differences divided by temperature of β″-(BEDT-TTF)2 SF5CH2CF2SO3 measured in different magnetic fields aligned parallel (open symbols) and 0.31° out of the conducting plane (closed symbols). The data are plotted offset for clarity.
Specific-heat differences, ΔC/T, of β″-(BEDTTTF)2SF5CH2CF2SO3 measured (a) at 10 T for different angles close to in-plane field orientation and (b) in different magnetic fields aligned 0.23° out of the conducting plane.
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