|Abstract:||In this thesis we consider the influence of dissipation on the charge transport
properties near the insulator-superconductor transition (IST) points in two dimensions. The first part is devoted to the description of the relevant experiments that motivated our work. After introducing the techniques necessary to handle the description near the IST, we consider the fluctuation
conductivity near the quantum critical point (QCP) in the presence of dissipation.
We show that sufficiently close to the QCP, Ohmic dissipation can change the dynamical critical exponent from z = 1 to z = 2 in the quantum critical (QC) regime. In the third part we show that the regularization of the conductivity resulting from the bosonic interactions on the 'insulating' (quantum disordered) (QD) side of an insulator-superconductor transition in 2D gives
rise to a metal with a finite conductivity, σ = (2/π)4e2/h, as temperature
tends to zero. Hence, we conclude that the traditionally-studied insulator-superconductor transition, which is driven solely by quantum fluctuations, corresponds to a superconductor-metal transition. In the fourth part we consider the fluctuation conductivity near the point of the IST in a system of Josephson junction arrays in the presence of both particle-hole asymmetry and Ohmic dissipation. We show that in the regions where a perturbative renormalization-group treatment is valid, coupling to an Ohmic heat bath leads to non-monotonic behavior of the dc conductivity
as a function of temperature. In the fifth part we analyze the behavior near the 2D IST in the presence of a perpendicular magnetic field. We show that with increasing field H,
the QD and QC regimes, in which vortex degrees of freedom are suppressed,
crossover to a new magnetically activated (MA) regime, where the correlation
length ξ ~ 1/√H. In this regime, we show that the conductivity decreases monotonically with field as opposed to the anticipated saturation predicted from hyper-universality arguments.