Квантовые осцилляции модуля параметра порядка в квазиодномерных сверхпроводниках
We investigate the influence of quantum phase fluctuations on electron density of states (DOS) in ultrathin superconducting films and nanowires. Using an effective action approach we derive a non-perturbative correction to DOS in such systems. The main effect of phase fluctuations in quasi-two-dimensional films is the appearance of electron states at subgap energies while in quasi-one-dimensional nanowires fluctuations also lead to smearing of the gap edge singularity in DOS.
The Low Temperature Physics Conference is an international event held every three years, under the auspices of the IUPAP through its Commission C5 on Low Temperature Physics. The aim of these conferences is to exchange information and views among the members of the international scientific community in the general field of Low Temperature Physics. It is a tradition that LT offers updates on the various topics, provided by the highest representatives of the field, as well as oral and poster contributions in the different areas. As usual the conference covers five subtopics:Quantum fluids and solids Superconductivity Cryogenic techniques and applications Magnetism and quantum phase transitions Quantum transport and quantum information in condensed matter
Gothenburg is situated in the center of Scandinavia, on the Swedish West Coast, and is easily accessed by air. The city’s two universities – Chalmers University of Technology and University of Gothenburg – both have a long tradition in low temperature physics research, particularly superconductivity and quantum transport.
Book of abstracts
We work out a microscopic theory describing complete statistics of voltage fluctuations generated by quantum phase slips (QPS) in superconducting nanowires. We evaluate the cumulant generating function and demonstrate that shot noise of the voltage as well as the thir d and all higher voltage cumulants differ from zero only due to the presence of QPS. In the zero-frequency limit voltage fluctuations in superconducting nanowires are described by Poisson statistics just as in a number of other tunnelinglike problems. However, at nonzero frequencies quantum voltage fluctuations in superconducting nanowires become much more complicated and are not anymore accounted for by Poisson statistics. In the case of short superconducting nanowires we explicitly evaluate all finite-frequency voltage cumulants and establish a nontrivial relation between these cumulants and the current-voltage characteristics of our system.
Simple measuring set-up was used to measure high-frequency impedance of superconducting Ti and NbN microstructures at low temperatures. The shift of resonance frequency below the temperature of superconducting transition compared to the normal state clearly indicates the increase of inductance of the system. The effect is interpreted as the impact of kinetic inductance originating from 'inertial' properties of Cooper pairs. Kinetic inductance of superconducting micro- and nanostructures should be taken into consideration for various cryoelectronic applications.
Superconducting properties of metallic nanowires can be entirely different from those of bulk superconductors because of the dominating role played by thermal and quantum fluctuations of the order parameter. For superconducting channels with diameters below ∼ 50 nm fluctuations of the phase of the complex order parameter - the phase slippage - lead to non-zero resistance below the critical temperature. Fluctuations of the modulus of the complex order parameter broaden the gap edge of the quasiparticle energy spectrum and modify the density of states. In extreme case of very narrow channels imbedded in high-impedance environment (which fix the charge and, hence, enable strong fluctuations of the quantum-conjugated variable, the phase) the superconductor can be driven to insulating state – the Coulomb blockade. We review recent experimental activities in the field demonstrating rather unusual phenomena.