Luttinger-liquid-like transport in long InSb nanowires

Long nanowires of degenerate semiconductor InSb in asbestos matrix (wire diameter is around 50 \AA, length 0.1 - 1 mm) were prepared. Electrical conduction of these nanowires is studied over a temperature range 1.5 - 350 K. It is found that a zero-field electrical conduction is a power function of the temperature $G\propto T^\alpha$ with the typical exponent $\alpha \approx 4$. Current-voltage characteristics of such nanowires are found to be nonlinear and at sufficiently low temperatures follows the power law $I\propto V^\beta$. It is shown that the electrical conduction of these nanowires cannot be accounted for in terms of ordinary single-electron theories and exhibits features expected for impure Luttinger liquid. For a simple approximation of impure LL as a pure one broken into drops by weak links, the estimated weak-link density is around $10^3-10^4$ per cm.Comment: 5 pages, 2 figure

Diffusion and Transport Coefficients in Synthetic Opals

Opals are structures composed of the closed packing of spheres in the size range of nano-to-micro meter. They are sintered to create small necks at the points of contact. We have solved the diffusion problem in such structures. The relation between the diffusion coefficient and the termal and electrical conductivity makes possible to estimate the transport coefficients of opal structures. We estimate this changes as function of the neck size and the mean-free path of the carriers. The theory presented is also applicable to the diffusion problem in other periodic structures.Comment: Submitted to PR

Optical properties of small polarons from dynamical mean-field theory

The optical properties of polarons are studied in the framework of the Holstein model by applying the dynamical mean-field theory. This approach allows to enlighten important quantitative and qualitative deviations from the limiting treatments of small polaron theory, that should be considered when interpreting experimental data. In the antiadiabatic regime, accounting on the same footing for a finite phonon frequency and a finite electron bandwidth allows to address the evolution of the optical absorption away from the well-understood molecular limit. It is shown that the width of the multiphonon peaks in the optical spectra depends on the temperature and on the frequency in a way that contradicts the commonly accepted results, most notably in the strong coupling case. In the adiabatic regime, on the other hand, the present method allows to identify a wide range of parameters of experimental interest, where the electron bandwidth is comparable or larger than the broadening of the Franck-Condon line, leading to a strong modification of both the position and the shape of the polaronic absorption. An analytical expression is derived in the limit of vanishing broadening, which improves over the existing formulas and whose validity extends to any finite-dimensional lattice. In the same adiabatic regime, at intermediate values of the interaction strength, the optical absorption exhibits a characteristic reentrant behavior, with the emergence of sharp features upon increasing the temperature -- polaron interband transitions -- which are peculiar of the polaron crossover, and for which analytical expressions are provided.Comment: 16 pages, 6 figure

Metallic Xenon, Molecular Condensates, and Superconductivity

A possibility of explaining the light absorption observed to occur under pressure-induced xenon metallization as due to the transition to the superconducting state is analyzed. The mechanism of the van der Waals bonding is discussed.Comment: LaTeX 2.09 (RevTeX), 4 pages, 4 PostScript figures included in tex

Melting Point and Lattice Parameter Shifts in Supported Metal Nanoclusters

The dependencies of the melting point and the lattice parameter of supported metal nanoclusters as functions of clusters height are theoretically investigated in the framework of the uniform approach. The vacancy mechanism describing the melting point and the lattice parameter shifts in nanoclusters with decrease of their size is proposed. It is shown that under the high vacuum conditions (p<10^-7 torr) the essential role in clusters melting point and lattice parameter shifts is played by the van der Waals forces of cluster-substrate interation. The proposed model satisfactorily accounts for the experimental data.Comment: 6 pages, 3 figures, 1 tabl

Bulk and local magnetic susceptibility of ErB12

High precision measurements of magnetoresistance Δρ/ρ = f(T,H) and magnetization M(T,H) were carried out on single crystals of rare-earth dodecaboride $ErB_{12}$ at temperatures in the interval 1.8-30 K in magnetic fields up to 70 kOe. The high accuracy of the experiments allowed us to perform numerical differentiation and analyze quantitatively the behavior of the derivative d(Δρ/ρ)/dH = f(T,H) and of the magnetic susceptibility χ(T,H) = dM/dH in paramagnetic and magnetically ordered (antiferromagnetic, $T_N$ ≈ 6.7 K and $T_M$ ≈ 5.85 K) phases of $ErB_{12}$. It was shown that negative magnetoresistance anomalies observed in present study in paramagnetic state of $ErB_{12}$ may be consistently interpreted in the framework of a simple relation between resistivity and magnetization -Δρ/ρ ~ $M^2$

Signatures of polaronic excitations in quasi-one-dimensional LaTiO3.41_{3.41}

The optical properties of quasi-one-dimensional metallic LaTiO$_{3.41}$ are studied for the polarization along the $a$ and $b$ axes. With decreasing temperature modes appear along both directions suggestive for a phase transition. The broadness of these modes along the conducting axis might be due to the coupling of the phonons to low-energy electronic excitations across an energy gap. We observe a pronounced midinfrared band with a temperature dependence consistent with (interacting) polaron models. The polaronic picture is corroborated by the presence of strong electron-phonon coupling and the temperature dependence of the dc conductivity.Comment: 5 pages, 5 figure

Rationality of the moduli spaces of plane curves of sufficiently large degree

We prove that the moduli space of plane curves of degree d is rational for all sufficiently large d.Comment: 18 pages; 1 figure; Macaulay2 scripts used can be found at http://www.uni-math.gwdg.de/bothmer/rationality/ or at the end of the latex source fil

Использование терапии на основе виртуальной реальности у пациентов после травматологических хирургических вмешательств: проспективное клиническое исследование

АКТУАЛЬНОСТЬ: Послеоперационная боль является распространенной проблемой. Использование немедикаментозных методов лечения может снизить потребность в лекарственных препаратах. Применение терапии на основе виртуальной реальности (ВР-терапия) широко изучается как метод дополнительного лечения при острой и хронической боли. Отсутствие данных об эффективности методики у пациентов после травматологических хирургических вмешательств стало основанием для проведения данного исследования. ЦЕЛЬ ИССЛЕДОВАНИЯ: Определить эффективность ВР-терапии как метода дополнительного лечения послеоперационной боли у пациентов после травматологических хирургических вмешательств. МАТЕРИАЛЫ И МЕТОДЫ: В проспективное клиническое исследование включены 70 пациентов, поступивших для выполнения плановых травматологических операций. ВР-терапию в комплексе с медикаментозными анальгетическими препаратами применили 35 пациентам. В контрольную группу включено 35 пациентов, которым после выполнения аналогичных хирургических вмешательств обезболивание осуществляли только медикаментозно. Терапию на основе ВР проводили с помощью устройства «Oculus Quest 2». Сеансы по 25 мин выполняли через 3, 7, 12 ч после операции. Оценку эффективности противоболевой терапии осуществляли с помощью числовой рейтинговой шкалы. Реакцию эндокринно-метаболического ответа на боль оценивали по изменению концентрации кортизола и адренокортикотропного гормона (АКТГ). РЕЗУЛЬТАТЫ: Терапия на основе медикаментозной анальгезии в комплексе с сеансами ВР приводила к лучшему качеству обезболивания пациентов после травматологических операций. После сеанса ВР-терапии снижение показателей по шкале самооценки боли составило 44 %. При сравнении с результатами, полученными на следующий день, значения в основной группе были ниже на 22 %. Достоверно снизилась потребность пациентов основной группы в наркотических анальгетиках. Изменение концентрации АКТГ как показателя эндокринно-метаболического ответа в группе с ВР-терапией было на 18 % менее выражено. ВЫВОДЫ: Применение ВР-терапии приводит к уменьшению показателей послеоперационной боли, эндокринно-метаболического ответа и потребности в опиоидных анальгетиках

Beyond single-photon localization at the edge of a Photonic Band Gap

We study spontaneous emission in an atomic ladder system, with both transitions coupled near-resonantly to the edge of a photonic band gap continuum. The problem is solved through a recently developed technique and leads to the formation of a ``two-photon+atom'' bound state with fractional population trapping in both upper states. In the long-time limit, the atom can be found excited in a superposition of the upper states and a ``direct'' two-photon process coexists with the stepwise one. The sensitivity of the effect to the particular form of the density of states is also explored.Comment: to appear in Physical Review