Static and dynamic image potential for tunneling into a Luttinger liquid

We study electron tunneling from a tip or a lead into an interacting quantum wire described by Luttinger liquid theory. Within a WKB-type approach, the Coulomb interaction between the wire and the tunneling electrons, as well as the finite traversal time are taken into account. Although the static image potential is only logarithmically suppressed against the bare Coulomb interaction, the dynamic image potential is not strong enough to alter power-law exponents entering the tunneling density of states.Comment: 4 pages, 2 figure

Thermalisation by a boson bath in a pure state

We consider a quantum system weakly coupled to a large heat bath of harmonic oscillators. It is well known that such a boson bath initially at thermal equilibrium thermalises the system. We show that assuming a priori an equilibrium state is not necessary to obtain the thermalisation of the system. We determine the complete Schr\"odinger time evolution of the subsystem of interest for an initial pure product state of the composite system consisting of the considered system and the bath. We find that the system relaxes into canonical equilibrium for almost all initial pure bath states of macroscopically well-defined energy. The temperature of the system asymptotic thermal state is determined by the energy of the initial bath state as the corresponding microcanonical temperature. Moreover, the time evolution of the system is identical to the one obtained assuming that the boson bath is initially at thermal equilibrium with this temperature. A significant part of our approach is applicable to other baths and we identify the bath features which are requisite for the thermalisation studied

Coulomb Blockade and Insulator-to-Metal Quantum Phase Transition

We analyze an interplay between Coulomb blockade and quantum fluctuations in a coherent conductor (with dimensionless conductance $g \gtrsim 1$) attached to an Ohmic shunt. We demonstrate that at T=0 the system can be either an insulator or a metal depending on whether its total resistance is larger or smaller than $h/e^2\approx 25.8$ k$\Omega$. In a metallic phase the Coulomb gap is fully suppressed by quantum fluctuations. We briefly discuss possible relation of this effect to recent experiments indicating the presence of a metal-insulator phase transition in 2d disordered systems.Comment: 4 revtex pages, no figure

Quantum Brownian Motion With Large Friction

Quantum Brownian motion in the strong friction limit is studied based on the exact path integral formulation of dissipative systems. In this limit the time-nonlocal reduced dynamics can be cast into an effective equation of motion, the quantum Smoluchowski equation. For strongly condensed phase environments it plays a similar role as master equations in the weak coupling range. Applications for chemical, mesoscopic, and soft matter systems are discussed and reveal the substantial role of quantum fluctuations.Comment: 11 pages, 6 figures, to appear in: Chaos: "100 years of Brownian motion

Quantum confinement corrections to the capacitance of gated one-dimensional nanostructures

With the help of a multi-configurational Green's function approach we simulate single-electron Coulomb charging effects in gated ultimately scaled nanostructures which are beyond the scope of a selfconsistent mean-field description. From the simulated Coulomb-blockade characteristics we derive effective system capacitances and demonstrate how quantum confinement effects give rise to corrections. Such deviations are crucial for the interpretation of experimentally determined capacitances and the extraction of application-relevant system parameters

Charge Fluctuations in the Single Electron Box

Quantum fluctuations of the charge in the single electron box are investigated. Based on a diagrammatic expansion we calculate the average island charge number and the effective charging energy in third order in the tunneling conductance. Near the degeneracy point where the energy of two charge states coincides, the perturbative approach fails, and we explicitly resum the leading logarithmic divergencies to all orders. The predictions for zero temperature are compared with Monte Carlo data and with recent renormalization group results. While good agreement between the third order result and numerical data justifies the perturbative approach in most of the parameter regime relevant experimentally, near the degeneracy point and at zero temperature the resummation is shown to be insufficient to describe strong tunneling effects quantitatively. We also determine the charge noise spectrum employing a projection operator technique. Former perturbative and semiclassical results are extended by the approach.Comment: 20 pages, 15 figure

High Temperature Conductance of the Single Electron Transistor

The linear conductance of the single electron transistor is determined in the high temperature limit. Electron tunneling is treated nonperturbatively by means of a path integral formulation and the conductance is obtained from Kubo's formula. The theoretical predictions are valid for arbitrary conductance and found to explain recent experimental data.Comment: 4 pages, 2 figure

Theory of electrostatically induced shape transitions in carbon nanotubes

A mechanically bistable single-walled carbon nanotube can act as a variable-shaped capacitor with a voltage-controlled transition between collapsed and inflated states. This external control parameter provides a means to tune the system so that collapsed and inflated states are degenerate, at which point the tube's susceptibility to diverse external stimuli-- temperature, voltage, trapped atoms -- diverges following a universal curve, yielding an exceptionally sensitive sensor or actuator that is characterized by a vanishing energy scale. For example, the boundary between collapsed and inflated states can shift hundreds of Angstroms in response to the presence or absence of a single gas atom in the core of the tube. Several potential nano-electromechanical devices can be based on this electrically tuned crossover between near-degenerate collapsed and inflated configurations

Two-instanton approximation to the Coulomb blockade problem

We develop the two-instanton approximation to the current-voltage characteristic of a single electron transistor within the Ambegaokar-Eckern-Sch\"on model. We determine the temperature and gate voltage dependence of the Coulomb blockade oscillations of the conductance and the effective charge. We find that a small (in comparison with the charging energy) bias voltage leads to significant suppression of the Coulomb blockade oscillations and to appearance of the bias-dependent phase shift