A. P. Levanyuk

Observation of ferroelectric domain structure branching and large step mobility on the TGS surface by atomic force and SNOM microscopy

Abstract We use atomic force microscopy(AFM) and scanning near field optical microscopy (SNOM) to study the TGS ferroelectric surface by monitoring its evolution in time and temperature by controlling the piezoelectric drifts. Experiments reveal a contrast which can be tentatively interpreted as evidence of theoretically predicted domain structure branching observed for the first time the in the range of 0.2 μ. The small features, presumably opposite polarity domains, are erasable by applying a voltage and by local illumination with argon laser light. In the paraelectric phase, unexpectedly large step mobilities are revealed. Also a complex character of the domain boundary structure is observed.

Low-temperature structural phase transitions: Phonon-like and relaxation order-parameter dynamics

A theoretical study on low-temperature structural phase transitions is presented, in which both phonon-like and relaxation order-parameter dynamics are contemplated. While the first limiting case has been considered previously, the second one is studied here for the first time. Attention is put on the low-temperature asymptotics of the temperature dependence of the generalized susceptibility. In the relaxation case, it is found

Elasticity-driven interaction between vortices in type-II superconductors

\sim (T^2 - T_c^2)^{-1}

Low-temperature specific heat of real crystals: Possibility of leading contribution of optical vibrations and short-wavelength acoustical vibrations

for temperature-independent relaxation times in a broad region of the temperature-pressure phase diagram. In contrast to the obtained in the phonon-like case, this asymptotics is not modified by long-range interactions (dipolar forces, piezoelectric effect, etc.).

Universal mechanism of discontinuity of commensurate-incommensurate transitions in three-dimensional solids: Strain dependence of soliton self-energy

The contribution to the vortex lattice energy which is due to the vortex-induced strains is calculated, covering all the magnetic-field range which defines the vortex state. The comparison with previously reported resultsshows that, in most of the vortex state, it has been notably underestimated until now. The assumption that only the vortex cores induce strains leads to this underestimation. In fact, all spatial variations of the order parameter induce strain. Core regions are important because here the order parameter varies strongly, but the non-core regions (smooth variations) might be even more important if their extension is large enough. It proves that in high-κ superconductors, in which the supercurrent regions with smooth variation of the order parameter are much more extended than the cores, the major contribution to the vortex-induced strains is due to the non-core regions.

Pseudoproper ferroelectricity in thin films

We point out that the repeatedly reported glasslike properties of crystalline materials are not necessarily associated with localized (or quasilocalized) excitations. In real crystals, optical and short-wavelength acoustical vibrations remain damped due to defects down to zero temperature. If such a damping is frequency independent---e.g., due to planar defects or charged defects---these optical and short-wavelength acoustical vibrations yield a linear-in-

Zero- T Transitions in Order-Disorder Systems: Displacive-Like Behavior

T

Fluctuation-induced interaction of domain walls

contribution to the low-temperature specific heat of the crystal lattices. At low enough temperatures such a contribution will prevail over that of the long-wavelength acoustical vibrations (Debye contribution). The crossover between the linear and Debye regimes takes place at

Striction-mediated attraction between domain walls: Main cause of the discontinuity of commensurate-incommensurate transitions

T*\ensuremath{\propto}\sqrt{N}

IMPOSSIBILITY OF OBSERVING A CONTINUOUS COMMENSURATE-INCOMMENSURATE TRANSITION

, where