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Register a new userNonextensive thermodynamics applied to superconductivity
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Added by
Lizardo H. C. M. Nunes
Publication date
2020
fields
Physics
and research's language is
English
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We have shown that the weak-coupling limit superconductors are well described by $ q sim 1 $, where $ q $ is a real parameter which characterizes the degree of nonextensivity of Tsallis entropy. Nevertheless, small deviations with respect to q=1 provide better agreement when compared with experimental results. We have also shown that the generalized BCS theory with $ q eq 1 $ exhibit power-law behavior of several measurable macroscopic functions in the low-temperature regime. These power-law properties are found in many high-Tc oxides superconductors and motivated us to extend Tsallis entropy calculations to these systems. Therefore, we have calculated the phase diagram and the specific heat and we compare our results with the experimental data for the YBCO compound.
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In this paper, we study the thermodynamics of quantum harmonic oscillator in the Tsallis framework and in the presence of a minimal length uncertainty. The existence of the minimal length is motivated by various theories such as string theory, loop quantum gravity, and black-hole physics. We analytically obtain the partition function, probability function, internal energy, and the specific heat capacity of the vibrational quantum system for $1<q<frac{3}{2}$ and compare the results with those of Tsallis and Boltzmann-Gibbs statistics without the minimal length scale.
We will present elementary scaling arguments focussed on the thermodynamics in the proximity of the quantum critical point in the cuprate superconductors. Extending the analysis centered on the Gruneisen parameter by Rosch, Si and coworkers to the cuprates, we demonstrate that a combination of specific heat- and chemical potential measurements can reveal the nature of the zero temperature singularity. From the known specific heat data it follows that the effective number of time dimensions has to equal the number of space dimensions, while we find a total of six scaling laws governing the temperature and density dependence of the chemical potential, revealing directly the coupling constant scaling dimension.
There is no accepted mechanism that explains the equilibrium structures that form in collisionless cosmological N-body simulations. Recent work has identified nonextensive thermodynamics as an innovative approach to the problem. The distribution function that results from adopting this framework has the same form as for polytropes, but the polytropic index is now related to the degree of nonextensiveness. In particular, the nonextensive approach can mimic the equilibrium structure of dark matter density profiles found in simulations. We extend the investigation of this approach to the velocity structures expected from nonextensive thermodynamics. We find that the nonextensive and simulated N-body rms-velocity distributions do not match one another. The nonextensive rms-velocity profile is either monotonically decreasing or displays little radial variation, each of which disagrees with the rms-velocity distributions seen in simulations. We conclude that the currently discussed nonextensive models require further modifications in order to corroborate dark matter halo simulations. (adapted from TeX)
The BCS-BEC crossover from strongly overlapping Cooper pairs to non-overlapping composite bosons in the strong coupling limit has been a long-standing issue of interacting many-body fermion systems. Recently, FeSe semimetal with hole and electron bands emerged as a high-$T_{rm c}$ superconductor located in the BCS-BEC crossover regime, owing to its very small Fermi energies. In FeSe, however, an ordinary BCS-like heat-capacity jump is observed at $T_{rm c}$, posing a fundamental question on the characteristics of the BCS-BEC crossover. Here we report on high-resolution heat capacity, magnetic torque, and scanning tunneling spectroscopy measurements in FeSe$_{1-x}$S$_x$. Upon entering the tetragonal phase at $x>0.17$, where nematic order is suppressed, $T_{rm c}$ discontinuously decreases. In this phase, highly non-mean-field behaviors consistent with BEC-like pairing are found in the thermodynamic quantities with giant superconducting fluctuations extending far above $T_{rm c}$, implying the change of pairing nature. Moreover, the pseudogap formation, which is expected in BCS-BEC crossover of single-band superconductors, is not observed in the tunneling spectra. These results illuminate highly unusual features of the superconducting states in the crossover regime with multiband electronic structure and competing electronic instabilities.
J. E. Hirsch [EPL 130 (2020) 17006] claimed an inconsistency between thermodynamics and the theory of superconductivity. We argue that he overlooked a crucial term which determines the supercurrent dynamics and ensures energy conservation by providing an internal energy source for the Joule heating. Thermodynamic consistency is restored by restoring energy conservation. The correct dynamics is given by Maxwells equations in the superconductor.
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