On the electric polarization of inhomogeneous superfluid systems

Rukin

2012

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The issue of adequate describing a gas of complex particles, composed of an even number of fermions, as point bosons is studied in alkali metals. In the low-density approximation we obtain the equation for the complex order parameter Φ(r1, r2) representing the wave function of atoms with taking into account the internal motion of the valence electrons. For superfluid systems formed by particles with internal degrees of freedom, this equation replaces the Gross-Pitaevskii equation. It is shown that, in general, exchange effects should be considered in the same approximation as effects of the direct interaction of atoms with each other. In particular, in the case of only the Coulomb interaction the neglect of exchange effects leads to qualitatively incorrect results. The problem of spontaneous polarization in superfluid systems is studied. The expression for the electric polarization of the inhomogeneous superfluid system is obtained.

Section: Resultsmentioning

confidence: 99%

Section: A Coherent State Of Fermion Pairsmentioning

confidence: 99%

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Two approaches to the description of dilute superfluid Bose systems

Rukin

2012

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“…Macroscopic spatial separation of the vortex charge and the compensating one allows to measure the electric field caused by these charges and to observe the motion of vortices in the superfluid. In this message we discuss the significant aspects of measuring the electric fields generated by the vortices.First we recall the arguments of the articles [14] - [16]. In a magnetic field H a rarefied medium moving with velocity v acquires polarizationHere α is the atom polarizability, n is the medium den- * Electronic address: shevchenko@ilt.kharkov.ua sity, c is the velocity of light.…”

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confidence: 99%

On electric fields created by quantized vortices

Rukin

2011

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It is shown that in a magnetic field quantized vortices in a superfluid obtain a real quantized electric charge concentrated in the vortex core. This charge is compensated by an opposite surface charge located at a macroscopic distance from the vortex axis. It is determined that the polarization caused by the vortex velocity field does not give rise to electric fields outside an infinite cylinder. Observation of electric fields created by the vortices is possible only near the end surfaces of the cylinder which must be closed with dielectric covers to prevent superfluid leaking. Influence of cover properties on the potential created by the vortex is researched. Potential created by the vortices on point and ring electrodes are calculated. were undertaken to understand the nature of the observed phenomena, but they are unsuccessful up to date. However, several interesting results were obtained which concern the mechanisms of polarization of both superfluid and normal systems. For example, in Melnikovskiy's article [4] it is shown that accelerated motion of a dielectric medium leads to its polarization proportional to the acceleration. Natsik [5] - [7] has studied the peculiarities of polarization of superfluid systems and, developing Melnikovskiy's ideas, has found that vortex motion of atoms in a superfluid must lead to their polarization caused by centrifugal force acting on them. In this case the polarization vector is directed normally to the velocity of the fluid moving around the vortex line, so the polarization vectors form a "hedgehog". Unfortunately, observation of electric fields caused by this "hedgehog" is rather difficult due to their rapid decrease with distance from the vortex line (reverse proportional to the cube of the distance). The authors [14] - [16] found that in a magnetic field the vortex line acquires a real electric charge whose magnitude is proportional to the vortex circulation and is quantized in the same way as the circulation. The compensating charge of the opposite sign appears on the surface of the system. Macroscopic spatial separation of the vortex charge and the compensating one allows to measure the electric field caused by these charges and to observe the motion of vortices in the superfluid. In this message we discuss the significant aspects of measuring the electric fields generated by the vortices.First we recall the arguments of the articles [14] -[16]. In a magnetic field H a rarefied medium moving with velocity v acquires polarizationHere α is the atom polarizability, n is the medium den- * Electronic address: shevchenko@ilt.kharkov.ua sity, c is the velocity of light. It follows from the common expression for the electric induction of the moving mediumwhere µ is the magnetic permeability, that the expression (1) for the dipole moment P is valid when µ = 1 and ǫ = 1 + 4πnα. In a superfluid there exists a "characteristic configuration" of the velocity field v caused by a vortex,Here φ is the phase of the order parameter. In the case of a rectilinear vortex in a uniform m...

“…In articles [41][42][43] polarization phenomena in 3D superfluid gas of electron-hole pairs (without spatial separation of electrons and holes) have been analyzed using an approach based on Keldysh's function. In [44] the Keldysh's approach has been applied to description of the superfluid state of a rarefied gas formed by alkali metal atoms.…”

Section: Introductionmentioning

confidence: 99%

Superfluidity of a dilute gas of electron-hole pairs in a bilayer system

Fil

2016

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The conditions of stability of the superfluid phase in double layer systems with pairing of spatially separated electrons and holes in the low density limit are studied. The general expression for the collective excitation spectrum is obtained. It is shown that under increase in the distance d between the layers the minimum emerges in the excitation spectrum. When d reaches the critical value the superfluid state becomes unstable relative to the formation of a kind of the Wigner crystal state. The same instability occurs at fixed d under increase in the density of carries. It is established that the critical distance and the critical density are related to each other by the inverse power function. The impact of the impurities on the temperature of the superfluid transition is investigated. The impact is found weak at the impurity concentration smaller than the density of the pairs. It is shown that in the rarefied system the critical temperature Tc ≈ 100 K can be reached.