Coherence in Transport Properties of Planar t-J-W Model

Peter Prelovšek, Janez Jaklič

Viacheslav Morosh, Julian Linek, B. Müller +9 more

We analyze electric transport and noise properties at 4.2 K of self-shunted superconductor-normal metal-superconductor (SNS) sandwich-type Josephson junctions, comprising $\mathrm{Nb}$ as the superconductor and $\mathrm{Hf}$-$\mathrm{Ti}$ as the normal conducting material, with lateral dimensions down to approximately $80$ nm. The junctions are fabricated with an optimized multilayer $\mathrm{Nb}$ technology based on nanopatterning by electron-beam lithography and chemical-mechanical polishing. The dependence of transport properties on the junction geometry (lateral size and barrier thickness ${d}_{\mathrm{Hf}\mathrm{\ensuremath{-}}\mathrm{Ti}}$) is studied, yielding a characteristic voltage ${V}_{c}$ up to approximately $100\phantom{\rule{0.2em}{0ex}}\ensuremath{\mu}\mathrm{V}$ for the smallest ${d}_{\mathrm{Hf}\mathrm{\ensuremath{-}}\mathrm{Ti}}=17$ nm. The observed small hysteresis in the current-voltage curves of devices with high ${V}_{c}$ and large size can be attributed to self-heating of the junctions and fitted with an extended version of the resistively shunted junction model. Measurements of voltage noise of single junctions are consistent with the model including self-heating effects. The potential of our technology for further miniaturization of nanoscale superconducting quantum interference devices and for the improvement of their performance is discussed.

Alvise Bastianello, Žiga Krajnik, Enej Ilievski

The classical Landau-Lifshitz equation-the simplest model of a ferromagnet-provides an archetypal example for studying transport phenomena. In one-spatial dimension, integrability enables the classification of linear and nonlinear mode spectrum. An exact characterization of finite-temperature thermodynamics and transport has nonetheless remained elusive. We present an exact description of thermodynamic equilibrium states in terms of interacting modes. This is achieved by retrieving the classical Landau-Lifschitz model through the semiclassical limit of the integrable quantum spin-S anisotropic Heisenberg chain at the level of the thermodynamic Bethe ansatz description. In the axial regime, the mode spectrum comprises solitons with unconventional statistics, whereas in the planar regime we find two additional types of modes of radiative and solitonic type. Our framework enables analytical study of unconventional transport properties: as an example we study the finite-temperature spin Drude weight, finding excellent agreement with Monte Carlo simulations.

Peter Prelovšek, Janez Jaklič

Gang Su

William Roger Fuller

Planar coherent states with domains in the complex plane are defined by means of ladder operators acting in a separable Hilbert space. Some properties of the states are derived and examples provided to indicate areas of possible applications.