Fermi Surface Structure and Isotropic Stability of Fulde-Ferrell-Larkin-Ovchinnikov Phase in Layered Organic Superconductor β″-(BEDT-TTF)2SF5CH2CF2SO3

The Fermi surface structure of a layered organic superconductor β″-(BEDT-TTF)2SF5CH2CF2SO3 was determined by angular-dependent magnetoresistance oscillations measurements and band-structure calculations. This salt was found to have two small pockets with the same area: a deformed square hole pocket and an elliptic electron pocket. Characteristic corrugations in the field dependence of the interlayer resistance in the superconducting phase were observed at any in-plane field directions. The features were ascribed to the commensurability (CM) effect between the Josephson vortex lattice and the periodic nodal structure of the superconducting gap in the Fulde–Ferrell–Larkin–Ovchinnikov (FFLO) phase. The CM effect was observed in a similar field region for various in-plane field directions, in spite of the anisotropic nature of the Fermi surface. The results clearly showed that the FFLO phase stability is insensitive to the in-plane field directions.

Topological acoustic triple point

Acoustic phonon is a classic example of triple degeneracy point in band structure. This triple point always appears in phonon spectrum because of the Nambu–Goldstone theorem. Here, we show that this triple point can carry a topological charge $${\mathfrak{q}}$$ q that is a property of three-band systems with space-time-inversion symmetry. The charge $${\mathfrak{q}}$$ q can equivalently be characterized by the skyrmion number of the longitudinal mode, or by the Euler number of the transverse modes. We call triple points with nontrivial $${\mathfrak{q}}$$ q the topological acoustic triple point (TATP). TATP can also appear at high-symmetry momenta in phonon and spinless electron spectrums when Oh or Th groups protect it. The charge $${\mathfrak{q}}$$ q constrains the nodal structure and wavefunction texture around TATP, and can induce anomalous thermal transport of phonons and orbital Hall effect of electrons. Gapless points protected by the Nambu–Goldstone theorem form a new platform to study the topology of band degeneracies.

Superconductivity in crystals with spin-orbit coupling

The electron Bloch states in crystals with spin-orbit coupling do not always transform under symmetry operations in the same way as the pure spin-1/2 states. This has profound consequences for the gap symmetry and nodal structure of superconductors. Based on the generalization of the Ueda–Rice prescription for the Bloch bases in twofold degenerate bands, we develop the general symmetry classification of multi-band superconducting pairing in non-magnetic centrosymmetric crystals. For the intraband pairing, we identify four exceptional cases in which the triplet gap function does not transform under the point group operations as a pseudovector, with a significant impact on the nodal structure. For the interband pairing, we show that the conventional ([Formula: see text]-wave) gap functions can have such unconventional features as triplet components and odd parity. The [Formula: see text]-wave interband pairing can also be odd in momentum and have a triplet component.

On the seismic activity of the Upper Kama potassium salt deposit

Introduction. The exploitation of the earth's subsoil on an industrial scale leads to a disturbance of equilibrium state of the geological environment and, as a consequence, to the manifestation of various dynamic events in it: sinkholes, rockbursts, induced earthquakes of various magnitudes, etc. Therefore, the problem of predicting such events or phenomena becomes urgent. About two dozen factors determining the state of geological environment and its dynamic regime have been identified in the course of solving this problem for the territory of Upper Kama (Verkhnekamskoe) potassium salt deposit (VKMKS): structural, tectonic, geomorphological, hydrogeological, hydrochemical, geophysical and others. Based on these factors-features, the zoning of the VKMKS territory was performed and the areas most likely for dynamic events manifestation were established. Among the factors-features stand out the dynamic events, which directly indicate the disturbance places of the geological environment’s equilibrium state. Among the features are the following: number and type of events, epicenters position, their relationship with the structural-tectonic elements of the geological environment’s structure and, first of all, with active faults. The purpose of this work is to compare the characteristics of a dynamic event that occurred in the area of SKRU-2 (Solikamsk mine-2) in 1995, with the geological structure of this area. Research methodology. The results of geological and geophysical studies carried out on the territory SKRU-2 are summarized, the characteristics of tectonic rockbursts are analyzed and the structuraltectonic and seismic data were compared. Research results. The structural-tectonic diagram of SKRU-2 territory was constructed and the relationship between the dynamic event and the structural features of the SKRU-2 territory was evaluated. Summary. The comparison of tectonic rockbursts characteristic and the structural-tectonic location of SKRU-2 territory has shown that the mine area is a nodal structure formed by active faults and complicated by fracture zones. Therefore, the probability of dynamic event focus development in such conditions is very high.

Unusual Trapped Mountain Lee Waves with Deep Vertical Penetration and Significant Stratospheric Amplitude

Simulations of the weather over the South Island of New Zealand on 28 July 2014 reveal unusual wave activity in the stratosphere. A series of short-wavelength perturbations resembling trapped lee waves were located downstream of the topography, but these waves were in the stratosphere, and their crests were oriented north–south, in contrast to both the northeast–southwest orientation of the spine of the Southern Alps and the crests of trapped waves present in the lower troposphere. Vertical cross sections through these waves show a nodal structure consistent with that of a higher-order trapped-wave mode. Eigenmode solutions to the vertical structure equation for two-dimensional, linear, Boussinesq waves were obtained for a horizontally homogeneous sounding representative of the 28 July case. These solutions include higher-order modes having large amplitude in the stratosphere that are supported by just the zonal wind component. Two of these higher-order modes correspond to trapped waves that develop in an idealized numerical simulation of the 28 July 2014 case. These higher-order modes are trapped by very strong westerly winds in the midstratosphere and are triggered by north–south-oriented features in the subrange-scale topography. In contrast, the stratospheric cross-mountain wind component is too weak to trap similar high-order modes with crest-parallel orientation.

Development of Preliminary Curved Bamboo Member Design Guidelines through Finite Element Analysis

Bamboo is emerging as a lightweight, versatile and renewable material that is projected to realise new methods of construction. There is a growing demand for using bamboo in different regions across the world. However, there are no specific design standards or guidelines that capitalise on the unique circular hollow cross section and internal nodal support of bamboo. Furthermore, there has been no strict analysis into how the curvature of bamboo members can help to better distribute stress through a structure. Bamboo is known as a more environmentally sustainable material than standard timber; however, due to the naturally occurring diaphragm nodal structure, it is less orthotropic in mechanical behaviour, with more out of plane stiffness than timber. To address this issue, this paper presents finite element analysis of three varying bamboo structures, each featuring a varying member curvature and lateral support system. In this paper, a preliminary set of design guidelines have been proposed for bamboo members, maximising the performance of its inherent mechanical properties. These guidelines propose the use of thick, low diameter bamboo members in axial loading and thin, high diameter members in flexural situations. Where available, the preliminary guidelines introduce the importance of curved bamboo members to uniformly distribute forces and crossing arched members to eliminate the need for lateral support systems, thereby reducing the total material required for construction. Finally, this report presents some novel consideration of the out-of-plane buckling of curved bamboo members–although for this purpose it does not consider the effect of the diaphragm components of bamboo, a source of future research and more comprehensive design guidelines.