Vortex-unbinding and finite-size effects inTl2Ba2CaCu2

Abstract

Current-voltage (I-V ) characteristics of Tl2Ba2CaCu2O8 thin films in zero magnetic field are measured and analyzed with the conventional Kosterlitz-Thouless-Berezinskii (KTB) approach, dynamic scaling approach and finite-size scaling approach, respectively. It is found from these results that the I-V relation is determined by the vortex-unbinding mechanism with the KTB dynamic critical exponent z = 2. On the other hand, the evidence of finite-size effect is also found, which blurs the feature of a phase transition.

Estimation of the critical dynamics and thickness of superconducting films and interfaces

“…In practice I − V -data exhibit resistive tails revealing finite size induced free vortices which make it difficult to estimate the transition temperature T c and the dynamical scaling exponent z. 3,4,5,6,7 Alternatively, the application of the conductivity relation (2) requires the explicit form of the correlation length. Since superconducting thin films and interfaces are expected to undergo a Berezinskii-Kosterlitz-Thouless (BKT) transition from the superconducting to the normal state the correlation length adopts for T ≥ T c the characteristic form 8,9…”

Collapses and revivals of exciton emission in a semiconductor microcavity: Detuning and phase-space filling effects

“…The coherent state is characterized by β = N exp(iφ) with the average exciton number N = |β| 2 and the initial phase φ. It should be pointed out that the definition of excitonic coherent state as the eigenstate of the annihilation operator of the excitons may work well only in the low exciton density regime [29]. This is because the expansion of a coherent state in the number state space will involve |N ex with large excitons number, which may destroy the weakly nonlinearity condition N A, N B ≪ g for the fixed g and A.…”