University of Illinois, Urbana

Title: Transport Properties near an Insulator-Superconductor Transition Point in the Presence of Dissipation

Abstract: We analyze the fluctuation conductivity near the point of a 2D insulator-superconductor transition (IST) in the presence of dissipation. When the dissipation is sufficiently weak, the conductivity acquires at the Gaussian level a logarithmic dependence on $T/m$ ($m$ is the inverse correlation length) in the renormalised classical regime. This dependence subsequently gives rise to a levelling of the resistivity at low to intermediate temperatures. Comparison with experiments which observe the levelling of the resistance on the `superconducting' side of the IST is made. In the quantum disordered regime, the regularization of the conductivity resulting from the quartic term in the underlying GL action gives rise to a metal on the 'insulating' side. This result holds also for the $z=2$ IST. The presence of dissipation or disorder reinstates the conventional insulating behavior. Consequently, our results imply that as long as translational invariance is intact or dissipation is absent, quantum fluctuations alone cannot give rise to an insulating state for bosons in 2D.