Gaussian Tunneling Model of c-Axis Twist Josephson Junctions

We calculate the critical current density $J^J_c$ for c-axis Josephson tunneling between identical high temperature superconductors twisted an angle $\phi_0$ about the c-axis. We model the tunneling matrix element squared as a Gaussian in the change of wavevector q parallel to the junction, $<|t({\bf q})|^2>\propto\exp(-{\bf q}^2a^2/2\pi^2\sigma^2)$. The $J^J_c(\phi_0)/J^J_c(0)$ obtained for the s- and extended-s-wave order parameters (OP's) are consistent with the Bi$_2$Sr$_2$CaCu$_2$O$_{8+\delta}$ data of Li {\it et al.}, but only for strongly incoherent tunneling, $\sigma^2\ge0.25$. A $d_{x^2-y^2}$-wave OP is always inconsistent with the data. In addition, we show that the apparent conventional sum rule violation observed by Basov et al. might be understandable in terms of incoherent c-axis tunneling, provided that the OP is not $d_{x^2-y^2}$-wave.Comment: 6 pages, 6 figure

Drying colloidal systems: laboratory models for a wide range of applications

The drying of complex fluids provides a powerful insight into phenomena that take place on time and length scales not normally accessible. An important feature of complex fluids, colloidal dispersions and polymer solutions is their high sensitivity to weak external actions. Thus, the drying of complex fluids involves a large number of physical and chemical processes. The scope of this review is the capacity to tune such systems to reproduce and explore specific properties in a physics laboratory. A wide variety of systems are presented, ranging from functional coatings, food science, cosmetology, medical diagnostics and forensics to geophysics and art

Unified low-energy effective Hamiltonian and the band topology of p-block square-net layer derivatives

In recent years, low-dimensional materials with tetragonal P4/nmm (orthorhombic Pnma) space group having square-net (chainlike) substructure of p-block elements have been studied extensively. By using a first-principles calculation and a two-sites &amp;#8855; two-orbitals tight-binding model, we construct the unified low-energy effective Hamiltonian and the Z2 topological phase diagram for such materials with different filling factors. Near the chemical potential, we show that the staggered arrangement of ions at 2c (4c) site yields a virtual hopping that has the same form with the second nearest-neighbor hopping between the square-net (chainlike) ions. We show that this hybridization and low-symmetry of the chainlike structure protects the quantum spin Hall insulator phase. Finally, the second-order spin-orbit coupling on top of the atomic spin-orbit coupling is considered to clarify the origin of the nonzero Berry phase signals reported in recent quantum oscillation experiments

Spin Polarization in γd

The study of spin observables is an important and active issue in low energy nuclear physics. In this contribution we report our recent calculation on the γd→ $\vec{n}$ p reaction at low photon energies. Our main goal is to calculate the neutron spin polarization Py′, but we also calculate the total cross section as well as the differential cross section. Although the results for the total and differential cross sections are found to agree reasonably well with the data, the results for Py′ show significant discrepancy with the experiment. We comment on this discrepancy

Frustration driven C-4 symmetric orders in a naturally heterostructured superconductor Sr2VO3FeAs

A subtle balance between competing interactions in iron-based superconductors (FeSCs) can be tipped by additional interfacial interactions in a heterostructure, often inducing exotic phases with unprecedented properties. Particularly when the proximity-coupled layer is magnetically active, rich phase diagrams are expected in FeSCs, but this has not been explored yet. Here, using high-accuracy 75As and 51V nuclear magnetic resonance measurements, we investigate an electronic phase that emerges in the FeAs layer below T0 ~ 155 K of Sr2VO3FeAs, a naturally assembled heterostructure of an FeSC and a Mottinsulating vanadium oxide. We find that frustration of the otherwise dominant Fe stripe and V Neel fluctuations via interfacial coupling induces a charge/orbital order in the FeAs layers, without either static magnetism or broken C4 symmetry, while suppressing the Neel antiferromagnetism in the SrVO3 layers. These findings demonstrate that the magnetic proximity coupling stabilizes a hidden order in FeSCs, which may also apply to other strongly correlated heterostructures. © The Author(s) 20171111sciescopu

Measurement of 137Cs in Ice Core Samples from Antarctica

Three different ice core samples from Antarctica were analyzed to identify activity concentrations of radioactive isotopes. Tracking migration of radioactive isotopes to Antarctica can provide a key clue to understand global environmental changes caused by radiation exposures because the Antarctic ice cores can preserve unique characteristics of various environmental conditions. We are particularly interested in the 137Cs nucleus, because it is closely related to radiation exposure from nuclear power plant accidents and nuclear bomb tests. With its half life of 30.17��0.03 years, 137Cs can also be used to assess the age of sedimentation occurring after around the year 1945. We selected three ice core samples, called Tarn8, Styx27, and H25, from different time periods; the Tarn8 sample is known to be from earlier than ~ 1000 AD, the Styx27 sample is approximately from the year 1945, and the H25 sample is from the year 2012. Radioactive isotope measurements of the ice core samples were performed using a 100% HPGe detector at Cheongpyeong Underground Radiation Laboratory (CURL). We measured the activity of 137Cs in the H25 sample to be 0.98 �� 0.82 mBq/kg. Although the activity has a large uncertainty mainly due to the limited sample quantity, the 137Cs isotopes in the Antarctic ice core were measured for the first time in Korea. (c)2018, The Korean Physical Society11Nsciescopuskc