A percolation model where carriers tunnel between metallic islands distributed in an insulating background is used to examine the electrical conductivity of underdoped cuprates above Tc. The process is thermally activated with an activation energy of the order of the Coulomb charging energy. The tunneling probability is described in terms of the distributions of the size r and separation s of the islands whose average values are increasing function of the doping. An insulating - like behaviour of the form ρ ≃ exp(To/T)1/4 is obtained at very low temperatures followed by a more metallic regime (ρ ≃ exp(Too/T)1/2) at higher temperatures. A comparison with experimental data in LASCO systems confirms the expected behaviour indicating a size of the regions ranging from 10A to 50A.
Effects of granular structure on the d.c transport in underdoped superconductors
DALLACASA, Valerio;
2003-01-01
Abstract
A percolation model where carriers tunnel between metallic islands distributed in an insulating background is used to examine the electrical conductivity of underdoped cuprates above Tc. The process is thermally activated with an activation energy of the order of the Coulomb charging energy. The tunneling probability is described in terms of the distributions of the size r and separation s of the islands whose average values are increasing function of the doping. An insulating - like behaviour of the form ρ ≃ exp(To/T)1/4 is obtained at very low temperatures followed by a more metallic regime (ρ ≃ exp(Too/T)1/2) at higher temperatures. A comparison with experimental data in LASCO systems confirms the expected behaviour indicating a size of the regions ranging from 10A to 50A.
I documenti in IRIS sono protetti da copyright e tutti i diritti sono riservati, salvo diversa indicazione.
