Electronic compressibility and charge imbalance relaxation in cuprate superconductors

In the material SmLa1−xSrxCuO4−δ with alternating intrinsic Josephson junctions we explain theoretically the relative amplitude of the two plasma peaks in transmission by taking into account the spatial dispersion of the Josephson Plasma Resonance in c direction due to charge coupling. From this and the magnetic field dependence of the plasma peaks in the vortex solid and liquid states it is shown that the electronic compressibility of the CuO2 layers is consistent with a free electron value. Also the London penetration depth λab ≈ 1100Å near Tc can be determined. The voltage response in the IV -curve of a Bi2Sr2CaCu2O8 mesa due to microwave irradiation or current injection in a second mesa is related to the nonequilibrium charge imbalance of quasiparticles and Cooper pairs and from our experimental data the relaxation time ∼ 100ps is obtained.