On electrical phenomena in electroneutral superfluid systems

Low Temperature Physics

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: A Homogeneous Casementioning

confidence: 97%

Section: A Coherent State Of Fermion Pairsmentioning

confidence: 99%

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Two approaches to the description of dilute superfluid Bose systems

Low Temperature Physics

Rukin

2012

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“…It can be shown [42] that at V ee (r) = V hh (r) = −V eh (r) (that corresponds to d = 0) the value of γ ex is positive. However, at d exceeding a certain critical value, the coefficient γ ex will change its sign.…”

Section: Energy Of the Electron-hole Coherent Statementioning

confidence: 99%

“…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

Low Temperature Physics

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.

On the Dipole Moment of Quantized Vortices in the Presence of Flows

Konstantinov

2016

J Low Temp Phys

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The polarization charge  of an inhomogeneous superfluid system is expressed as a function of the order parameter 1 2 ( , )  r r . It is shown that if the order parameter changes on macroscopic distances, the polarization charge pol  is proportional to 2 A n  , and the polarization P is proportional to A n  , where n is the density of the system. For noninteracting atoms the proportionality coefficient A is independent of density, and in the presence of interaction A is proportional to n . The change of the Bose gas density is found in the presence of a flow n s   w v v passing the vortex. It is found that a vortex in a superfluid film creates an electric potential above the film. This potential has the form of a potential of a dipole, allowing to assign a dipole moment to the vortex. The dipole moment is a sum of two terms, the first one is proportional to the relative flow velocity w and the second one isExperiments [1,2] carried out at ILT in Kharkov last 10 years revealed that a standing wave of second sound in He II was accompanied by appearance of electric potential of the order 7