Effect of local Coulomb interaction on Majorana corner modes: weak and strong correlation limits

Here we present an analysis of the evolution of Majorana corner modes realizing in a higher-order topological superconductor (HOTSC) on a square lattice under the influence of local Coulomb repulsion. The HOTSC spectral properties were considered in two regimes: when the intensities of many-body interactions are either weak or strong. The weak regime was studied using the mean-field approximation with self-consistent solutions carried out both in the uniform case and taking into account of the boundary of the finite square-shaped system. It is shown that in the uniform case the topologically nontrivial phase on the phase diagram is widened by the Coulomb repulsion. The boundary effect, resulting in an inhomogeneous spatial distribution of the correlators, leads to the appearance of the crossover from the symmetric spin-independent solution to the spin-dependent one characterized by a spontaneously broken symmetry. In the former the corner states have energies that are determined by the overlap of the excitation wave functions localized at the different corners. In the latter the corner excitation energy is defined by the Coulomb repulsion intensity with a quadratic law. The crossover is a finite size effect, i.e. the larger the system the lesser the critical value of the Coulomb repulsion. In the strong repulsion regime we derive the effective HOTSC Hamiltonian in the atomic representation and found a rich variety of interactions induced by virtual processes between the lower and upper Hubbard subbands. It is shown that Majorana corner modes still can be realized in the limit of the infinite repulsion. Although the boundaries of the topologically nontrivial phase are strongly renormalized by Hubbard corrections.Comment: 13 pages, 6 figure

Влияние комплекса хитозан-ß-циклодекстрин с левофлоксацином на микрофлору ран и толстого кишечника осетра

The authors in the article presented the results of determining the effectiveness of using the chitosan-ß-cyclodextrin complex with levofloxacin in the healing of mechanical wounds of valuable commercial fish sturgeons and their feeding. The experiment was conducted based on the “Progressive biotechnologies in aquaculture” research laboratory of the Saratov State University of Genetics, Biotechnology and Engineering. N.I. Vavilov. The microflora of incised wounds and the large intestine of sturgeon fingerlings under the influence of fluoroquinolone, represented by levofloxacin based on cyclodextrin, included in the shell of high-molecular chitosan, was studied. The studied microbiological indicators were chosen to determine that changes in the total number of microorganisms show the nature of the course of the inflammatory/pathological process, which contributes to the development of microorganisms (including opportunistic pathogens) and lactic acid bacteria in the intestine. Therefore, they are essential physiological indicators of the formation of “ intestinal immunity. It was found that the use of cyclodextrin with levofloxacin in the treatment of incised wounds in sturgeons leads to a significant decrease in the total microbial number (TMC) on their surface (by 10 thousand times compared to the group without treatment). It has been shown that using cyclodextrin with levofloxacin in feeding sturgeons reduces the total microbial number in the large intestine. This complex is characterised by good solubility and bioavailability for fish. The future study results can be used in aquaculture to treat mechanical injuries received during transportation and sorting in the rearing process in fish.Представлены результаты определения эффективности применения комплекса хитозан-ß-циклодекстрин с левофлоксацином в заживлении механических ран ценных промысловых рыб – осетров и их кормлении. Эксперимент проводили на базе научно-исследовательской лаборатории «Прогрессивные биотехнологии в аквакультуре» Саратовского государственного университета генетики, биотехнологии и инженерии им. Н.И. Вавилова. Исследовалась микрофлора резаных ран и толстого кишечника сеголетков осетров под действием фторхинолона, представленного левофлоксацином на основе циклодекстрина, включенного в оболочку высокомолекулярного хитозана. Исследуемые микробиологические показатели были выбраны для определения на том основании, что изменения общего количества микроорганизмов показывают характер течения воспалительного/патологического процесса, способствующего развитию микроорганизмов (в т.ч. условно-патогенных) и молочнокислых бактерий в кишечнике, поэтому являются важными физиологическими показателями формирования «кишечного иммунитета». Было обнаружено, что применение при лечении резаных ран у осетров циклодекстрина с левофлоксацином приводит к значительному уменьшению общего микробного числа (ОМЧ) на их поверхности (в 10 тыс. раз по сравнению с группой без лечения). Показано, что использование в кормлении осетров циклодекстрина с левофлоксацином также снижает общее микробное число в толстом кишечнике. Данный комплекс характеризуется хорошей растворимостью и биодоступностью для рыб. Результаты исследования в перспективе могут найти применение в аквакультуре при лечении механических травм, полученных при перевозке и сортировке в процессе выращивания, у рыб

Majorana vortex modes in spin-singlet chiral superconductors with noncollinear spin ordering: Local density of states study

In the present study topologically nontrivial edge and vortex bound states are described in the coexistence phase of chiral spin-singlet superconductivity and noncollinear spin ordering on a triangular lattice. Since chiral superconductivity is nodeless in a wide range of parameters, the obtained bound states are separated from trivial bulk states. It is proved that Majorana modes localized at vortex cores are caused by noncollinear long-range magnetic ordering. Even though nearby excitation energies of subgap states including the edge-localized and vortex-localized states are very close to each other, the energy difference between different vortex bound states is an order of magnitude higher. It opens the way to experimentally detect the zero energy Majorana modes localized at vortex cores in the considered structures by using methods measuring local density of states such as tunneling experiments. For a few pairs of vortices, vortex bound states with near zero energy can appear. Nevertheless, they are localized on different vortices in comparison with the localization of Majorana vortex modes. In this case zero modes are still separated in energy and space from other states in local density of states results. The difference between density of states near the vortex and near the antivortex hosting Majorana modes is also demonstrated.Comment: 10 pages, 10 figure

Hierarchical Calcite Crystals with Occlusions of a Simple Polyelectrolyte Mimic Complex Biomineral Structures

Biominerals are complex inorganic-organic structures that often show excellent mechanical properties. Here a bio-inspired study of a remarkably simple synthetic system is presented in which only one charged polymer additive (poly(sodium 4-styrenesulfonate)) is able to induce hierarchical structuring of calcite similar to biominerals. The interaction of the negatively charged polymer with the nucleation and growth of the mineral, in particular via selective adsorption to internal and external (001) facets of the calcite lattice, implies structural features from the micrometer down to the nanometer level. The crystals exhibit a distinct rounded morphology and a controlled orientation. Moreover, the polymer molecules are occluded within the crystals with different concentrations in well-defined regions. This leads to the induction of a mesoscale structure based on 100 nm sized mineral building blocks with granular substructure and rough surface, as well as small modifications of the crystallographic structure. Such a combination of hierarchically organized structural features has previously only been reported for biogenic calcite, which is typically grown in a complex process involving multiple organic additives. It is also shown that the organic occlusions in the calcite-PSS hybrid crystals strongly affect the mechanical performance, as known for some biominerals

Micro- and nano-structural details of a spider's filter for substrate vibrations : relevance for low-frequency signal transmission

The metatarsal lyriform organ of the Central American wandering spider Cupiennius salei is its most sensitive vibration detector. It is able to sense a wide range of vibration stimuli over four orders of magnitude in frequency between at least as low as 0.1 Hz and several kilohertz. Transmission of the vibrations to the slit organ is controlled by a cuticular pad in front of it. While the mechanism of high-frequency stimulus transfer (above ca 40 Hz) is well understood and related to the viscoelastic properties of the pad's epicuticle, it is not yet clear how low-frequency stimuli (less than 40 Hz) are transmitted. Here, we study how the pad material affects the pad's mechanical properties and thus its role in the transfer of the stimulus, using a variety of experimental techniques, such as X-ray micro-computed tomography for three-dimensional imaging, X-ray scattering for structural analysis, and atomic force microscopy and scanning electron microscopy for surface imaging. The mechanical properties were investigated using scanning acoustic microscopy and nanoindentation. We show that large tarsal deflections cause large deformation in the distal highly hydrated part of the pad. Beyond this region, a sclerotized region serves as a supporting frame which resists the deformation and is displaced to push against the slits, with displacement values considerably scaled down to only a few micrometres. Unravelling the structural arrangement in such specialized structures may provide conceptual ideas for the design of new materials capable of controlling a technical sensor's specificity and selectivity, which is so typical of biological sensors