arXiv subjects

A. V. Nikulov

Publications and source records attributed to A. V. Nikulov.

78 records · Page 5Linked to original sources

arXiv1999

About Perpetuum Mobile without Emotions

One of the oldest science problems - possibility of the perpetuum mobile is discussed. The interest to this problem was provoke a result, published in J. Low Temp.Phys. 112, 227 (1998); cond-mat/9811148, which contradicts to the second law of thermodynamics. According to this result, the thermal fluctuations can induce a voltage with direct component in a inhomogeneous superconducting ring at an unaltered temperature corresponded to the resistive transition of the ring segment with the lowest critical temperature. This result arises from obvious statements: 1) the switching of a ring segment $l_{b}$ into and out of the normal state, while the rest of the ring (segment $l_{a}$) remains superconducting, can induced a voltage with dc component (It is shown that, in spite of the wide spread opinion, this statement is correct because the superconductivity is a macroscopic quantum phenomena); 2) the thermal fluctuations switch the mesoscopic ring segment $l_{b}$ with lowest critical temperature $T_{sb}$ into and out of the normal state at $T \simeq T_{sb}$, while the rest of the ring remains superconducting if $T_{sa} > T \simeq T_{sb}$. In order to resolve the contradiction between these obvious statements and the second law of thermodynamics a possibility of the second order perpetuum mobile is considered theoretically. It is shown that from two type of the perpetuum mobile, only type "b" and only in quantum systems is possible. According to the presented interpretation, the total entropy, as the measure of the chaos, may be systematically reduced in some quantum system because a "switching" between the classical and quantum mechanics is possible. Instruction for the making of the perpetuum mobile is enclosed.

physics.gen-ph↗

arXiv1999

Comparison of the fluctuation influence on the resistive properties of the mixed state of BiSrCaCuO and of thin films of conventional superconductor

The resistive properties of layered HTSC BiSrCaCuO in the mixed state are compared with those of thin films of conventional superconductors with weak disorders (amorphous Nb_{1-x}0_{x} films) and with strong disorders (Nb_{1-x}O_{x} films with small grain structure). The excess conductivity is considered as a function of superconducting electron density and phase coherence length. It is shown that the transition to the Abrikosov state differs from the ideal case both in BiSrCaCuO and Nb_{1-x}O_{x} films, i.e. the appearance of long-range phase coherence is continuous transition in both cases. The quantitative difference between thin films with weak and strong disorders is greater than the one between layered HTSC and conventional superconductors, showing that the dimensionality of the system, rather than the critical temperature, is the key factor ruling fluctuation effects

cond-mat.supr-con↗

arXiv1999

Transformation of Thernal Energy in Electric Energy in an Inhomogeneous Superconducting Ring

It is shown that a heat energy can be transformed in an electric energy of direct current by the use of an inhomogeneous superconducting ring. This trasformation is possible both at an iterative change of temperature and at an unaltered temperature. In the first case the ring is a classical heat engine with a maximum efficiency in the Carno cycle. The second case contradicts to the second thermodynamic law formulated in the middle of last century. Nevertheless this result is correct because the thermal fluctuation is an opposite (relatively of the second thermodynamic law) consequence of the law of entropy increase. In order to introduce some order into the chaotic energy of the thermal fluctuations a preferential direction should exist. Such preferential direction of superconducting electron motion exists in a ring if a magnetic flux is not divisible by the flux quantum.

cond-mat.supr-con↗

arXiv1998

Phase Coherence Appearance in Thin Superconducting Film with Strong Disorders. The Return to the Mendelssohn Model

It is shown that transition from the mixed state without the phase coherence to the mixed state with the long-range phase coherence (i.e. to the Abrikosov state) of superconductors without disorder must be first order phase transition. The phase coherence appearance in thin superconducting film with strong disorder is considered. The observed smooth transition is explained by increasing of the effective fluctuation dimensionality (from zero to one) in superconductors with strong disorder. Mendelssohn model is used for the explanation of the resistive properties of film with strong disorder.

cond-mat.supr-con↗

arXiv1998

The Little-Parks effect in an inhomogeneous superconducting ring

An inhomogeneous superconducting ring placed in a magnetic field is considered. It is shown that the superconducting transition of the section with lowest critical temperature may be a first order phase transition if the magnetic flux contained within the ring is not divisible by the flux quantum. In the visinity of this transition, thermal fluctuations can induce the direct voltage in the ring with rather small sizes. The voltage value depends in a periodic manner on the magnetic flux contained within the ring. According to this result, the entropy value can be decreased in the considered quantum system. The chaotic heat energy can be transformed in the electric energy of the direct current.

cond-mat.supr-con↗

arXiv1998

The vortex lattice melting theory as example of science fiction

The concept of the transition of type II superconductor into the Abrikosov state as the appearance of long-range phase coherence is considered. It is shown that this transition should be first order in ideal (without disorder) superconductor. Such transition is indeed observed in bulk superconductors with weak disorder at a field Hc4 < Hc2. No experimental evidence of the vortex lattice melting exists now. It is shown that this popular concept has appeared on a consequence of an incorrect interpretation of the Abrikosov state and incorrect definition of the phase coherence. The absence of a sharp transition in thin films with weak disorder is interpreted as absence of long-range phase coherence down to very low magnetic field. In order to explain the observed smooth phase coherence appearance in superconductors with strong disorder it is proposed to return to the Mendelssohn model.

cond-mat.supr-con↗