We present large sets of data for the microwave complex resistivity (48 and 21 GHz) in cuprate superconductors thin films in moderate magnetic fields (B<1.5 T) and for temperatures above 60 K. We have investigated the vortex state microwave response in YBa2Cu3O7–d (YBCO), SmBa2Cu3O7–d (SmBCO) and Bi2Sr2CaCu2O8+x (BSCCO). The data are taken with the end-wall replacement technique, using several different resonant cavities and geometrical configurations. In the lowest frequency setup, the magnetic field could rotate in the (a,b) plane, varying the angle between the dc field and the microwave currents. A second setup was used to change the angle between the dc field and the (a,b) planes. A systematic of the microwave response is performed in YBCO, SmBCO, BSCCO at 48 GHz with the field directed along the c axis. At this frequency, we do not observe appreciable flux-creep effects in any of the investigated samples. Pinning appears to be negligible in the field and temperature range under investigation. However, all samples investigated present a clear sublinear dc field dependence of both real and imaginary part of the resistivity, that cannot be accounted for by free-flux flow models. This effect can be interpreted in the framework of increased quasiparticle response in superconductors with lines of nodes in the gap. Once the quasiparticle response is identified, vortex viscosity is also extracted. In YBCO we have also investigated the response as a function of frequency (6-20 GHz) through a Corbino disk technique, varying the field up to 8 T. Excellent agreement is obtained for the dynamical vortex parameters (viscosity and pinning frequency). Finally, we have investigated in YBCO the response in the rarely employed configuration with the field parallel to the (a,b) planes, by changing the angle between the field and the transport current. The sin2a pattern, typical of the Lorentz-force-driven fluxon motion is observed. A significant dissipation, even for the field parallel to the current (Lorentz-force-free configuration), is also detected. We discuss this effect in terms of quasiparticle response. We extract the pure vortex resistivity in the maximum lorentz-force configuration. Effective vortex viscosity is measured, and intrinsic-pinning frequency is obtained.
Silva, E., Pompeo, N., Marcon, R., Fastampa, R., Giura, M., Sarti, S. (2004). Vortex state microwave response in high-Tc superconducting films.
Vortex state microwave response in high-Tc superconducting films
POMPEO, NICOLA;MARCON, Romolo;
2004-01-01
Abstract
We present large sets of data for the microwave complex resistivity (48 and 21 GHz) in cuprate superconductors thin films in moderate magnetic fields (B<1.5 T) and for temperatures above 60 K. We have investigated the vortex state microwave response in YBa2Cu3O7–d (YBCO), SmBa2Cu3O7–d (SmBCO) and Bi2Sr2CaCu2O8+x (BSCCO). The data are taken with the end-wall replacement technique, using several different resonant cavities and geometrical configurations. In the lowest frequency setup, the magnetic field could rotate in the (a,b) plane, varying the angle between the dc field and the microwave currents. A second setup was used to change the angle between the dc field and the (a,b) planes. A systematic of the microwave response is performed in YBCO, SmBCO, BSCCO at 48 GHz with the field directed along the c axis. At this frequency, we do not observe appreciable flux-creep effects in any of the investigated samples. Pinning appears to be negligible in the field and temperature range under investigation. However, all samples investigated present a clear sublinear dc field dependence of both real and imaginary part of the resistivity, that cannot be accounted for by free-flux flow models. This effect can be interpreted in the framework of increased quasiparticle response in superconductors with lines of nodes in the gap. Once the quasiparticle response is identified, vortex viscosity is also extracted. In YBCO we have also investigated the response as a function of frequency (6-20 GHz) through a Corbino disk technique, varying the field up to 8 T. Excellent agreement is obtained for the dynamical vortex parameters (viscosity and pinning frequency). Finally, we have investigated in YBCO the response in the rarely employed configuration with the field parallel to the (a,b) planes, by changing the angle between the field and the transport current. The sin2a pattern, typical of the Lorentz-force-driven fluxon motion is observed. A significant dissipation, even for the field parallel to the current (Lorentz-force-free configuration), is also detected. We discuss this effect in terms of quasiparticle response. We extract the pure vortex resistivity in the maximum lorentz-force configuration. Effective vortex viscosity is measured, and intrinsic-pinning frequency is obtained.I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
