Aleksandr F. Andreev

Supersolidity of glasses

The supersolidity of glasses is explained as the property of an unusual state of condensed matter. This state is essentially different from both normal and superfluid solid states. The mechanism of the phenomenon is the transfer of the mass by tunneling two-level systems.

Macroscopic magnetic fields of antiferromagnets

The macroscopic magnetic fields arising in the space outside or in the bulk of an antiferromagnet in the absence of external currents are a result of surface magnetization. The general problem of determining these fields is formulated. It is shown that the field distribution near special lines on the surface is monopolar. An experimental study of the field makes it possible to determine the surface magnetization on the faces of an antiferromagnetic crystal.

Gap and subgap tunnelling in cuprates

We describe strongly attractive carriers in cuprates in the framework of a simple quasi-one-dimensional Hamiltonian with a local attraction. In contrast with the conventional BCS theory, there are two energy scales, a temperature-independent incoherent gap Δp and a temperature-dependent coherent gap Δc(T) combining into one temperature-dependent global gap Δ = (Δp2 + Δc2)1/2. The temperature dependence of the gap and single-particle (Giaver) tunnelling spectra in cuprates are quantitatively described. Two distinct energy scales observed in Giaver tunnelling and electron-hole reflection experiments are understood and their link with the zero-bias conductance peak and the symmetry of the order parameter is discussed.

Momentum deficit in quantum glasses

Using the concept of tunneling two-level systems, we explain the reduction of rotational inertia of disordered solid 4He observed in the torsional oscillator experiments. The key point is a peculiar quantum phenomenon of momentum deficit for two-level systems in moving solids. We show that an unusual state that is essentially different from both normal and superfluid solid states can be realized in quantum glasses. This state is characterized by reduced rotational inertia in oscillator experiments, by the absence of a superflow, and by the normal behavior in steady rotation.Using the concept of tunneling two level systems we explain the reduction of rotational inertia of disordered solid He observed in the torsional oscillator experiments. The key point is a peculiar quantum phenomenon of momentum deficit for two level systems in moving solids. We show that an unusual state which is essentially different from both normal and superfluid solid states can be realized in quantum glasses. This state is characterized by reduced rotational inertia in oscillator experiments, by absence of a superflow, and by normal behavior in steady rotation. PACS numbers: 67.80.-s

Electron pairs for HTSC

AbstractA simple physical picture of superconductivity is proposed for extremely doped CuO2 planes. It possesses features that are observed for HTSC, such as a high superconducting transition temperature,

Bose condensation and spontaneous breaking of the uniformity of time

d_{x^2 - y^2 }

Low-temperature anomalies of 4He crystals

the symmetry of order parameter, and the coexistence of a one-electron Fermi surface and the Bose-Einstein condensate of preformed electron pairs.

Manifestation of additional dimensions of space-time in mesoscopic systems

New, superfluid specific additive integral of motion is found. This facilitates investigation of general thermodynamic equilibrium conditions for superfluid. The analysis is performed in an extended space of thermodynamic variables containing (along with the usual thermodynamic coordinates such as pressure and temperature) superfluid velocity and momentum density. The equilibrium stability conditions lead to thermodynamic inequalities which replace the Landau superfluidity criterion at finite temperatures.