Results 1 - 10 of 411
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[en] The role of nematic fluctuations in the appearance of high temperature superconductivity is still controversial. In this work we investigate the phase diagrams of BaFeAs and LaFeAsO as a function of electron-doping through elastotransport and Nernst effect measurements. We obtain an anomalously large Nernst coefficient in the tetragonal phase, upon doping its magnitude strikingly mimicking the superconducting dome. Similar but slightly different non-monotonic behavior is found for the elastoresistivity. Using a minimal orbital model for iron-based superconductors we show that the Nernst coefficient couples directly to the nematic fluctuations. We explain the difference between elastoresistivity and Nernst effect by incorporating the coupling to a soft phonon mode in our theory. Thus, our experimental results provide supportive evidence that nematic fluctuations are crucial for the formation of the superconducting state in iron-based superconductors.
[en] In Weyl semimetals the Nernst coefficient is dominated by anomalous contributions to the electrical and thermal conductivity which originate from a specific property of the underlying system of conduction electrons, the Berry curvature. Motivated by recent experiments on the prototypical type-I Weyl semimetals TaP and TaAs we explain the measured anomalous field dependence of the Nernst coefficient in terms of a minimal model of the energy dispersion near two separated Dirac nodes. On the basis of this result we argue that our observed field dependence of the Nernst effect can straightforwardly be explained by a characteristic change of the chemical potential under variation of the external magnetic field which is applied to obtain the Nernst effect.
[en] In this work, the transport mechanism of the Sr''2+ ions through inorganic membranes of barium phospho silicate was modelled by means of the theory that led to the equation of Nerst-Planck, due to its better representation of the electrodialysis system utilised. The model permitted to fit the experimental information, regarding the variation in concentration of Sr''2+ ion over time, obtained in an electrodialysis cell under a constant electric field. (Author) 10 refs
[en] An HTSC model, in which the interaction of valence-band electrons with diatomic negative U centers is assumed to be responsible for the anomalous properties of HTSC compounds, is proposed and used to explain the nature of the pseudogap and pseudogap anomalies (including the giant Nernst effect, the anomalous diamagnetism above Tc, the 'transfer' of the optical spectral weight). For YBa2Cu3O6+δ, the pseudogap opening temperature T* and Tc are calculated as functions of the degree of doping δ. The calculated dependences agree quantitatively with the experimental dependences without using scale fitting parameters. The good agreement between the calculated and experimental results can serve as an argument for the proposed HTSC model
[en] A device for investigation of thermo- and galvanomagnetic transverse effects by means of a new dynamic method is described. For the first time the temperature dependence of the isothermic and adiabatic Nernst-Ettingshausen coefficient S123 of Sb2Te3 was measured. The results differ qualitatively from those which have been found by other authors at the isomorphic crystal Bi2Te3. (author)
[en] A semi empirical model was developed to characterize the transport of cupric ions within the Nernst layer generated between electrolyte bulk and the membrane surface in an electrodialysis cell. The model was derived from fundamental equations and was reduced to a linear expression incorporating the cupric ion transport number in the Nernst layer (t+BL) and in the membrane (t+m). The model critical condition is t+BL <0.5 t+m. The model correctly fits the experimental data when t+BL is o.02. the model was validated with experimental results previously published by the authors and it accounts for a linear concentration gradient within the Nernst layer. (Author) 28 refs
[en] Many experiments on the Nernst effect have been presented as an evidence of the Cooper pairs without phase coherence. Here we present calculations with the local superconducting theory of Bogoliubov-de Gennes (BdG) on a charge disordered system whose onset temperature of superconducting regions are in good agreement with Nernst experiments
[en] The author demonstrates that in the presence of pinning a simple relation exists between Nernst and Seebeck coefficients and the resistivity tensor, based on the vortex equation of motion and the two-fluid model. Thus the combination of the electric and thermoelectric transport experiments can be used to test the basic models for the vortex dynamics in superconductors. Then the author shows how two different vortex dynamics models can be subjected to these tests. The vortex dynamics model without various normal fluid drag forces is consistent with those experiments, and that the alternative model with those drag forces is not
[en] A new magnetic field generation mechanism in radiation-heated plasma is considered. This mechanism is based on the Nernst effect and operates in plasma with oppositely directed temperature and density gradients. The efficiency of the mechanism is determined by the values of these gradients.
[en] Highlights: • A pure spin Nernst effect can be obtained and manipulated electrically. • A fully spin-polarized Nernst effect with tunable spin direction can be obtained. • Some phase windows for creating nearly fully spin-polarized Nernst effect exist. • The width of the windows is controllable by the other phase. • We show some symmetry properties of the spin and charge Nernst coefficients. - Abstract: We investigate the spin and charge Nernst effect of a four-terminal Aharonov–Bohm interferometer with Rashba spin–orbit interaction (RSOI). It is shown that a pure spin Nernst effect or a fully spin-polarized Nernst effect can be obtained by modulating the magnetic flux phase ϕ and the RSOI induced phase φ. It is also demonstrated that some windows of ϕ (or φ) for maintaining an almost fully spin-polarized Nernst effect exist and their width is under the control of the other phase. Moreover, for the charge Nernst coefficient and spin Nernst coefficient the relationship always holds. These results suggest that our proposal may act as a controllable thermospin generator.