Spin-glass behavior in the antiperovskite manganese nitride Mn3CuN codoped with Ge and Si

Antiperovskite manganese nitrides ${\mathrm{Mn}}_3\left({\mathrm{Cu}}_{0.6}{\mathrm{Si}}_x{\mathrm{Ge}}_{0.4?x}\right)N$ ($x=0.05$, 0.1, 0.15) were prepared and their negative thermal expansion, magnetic and specific heat properties were investigated. A frozen state with a freezing temperature was found at ～207 K in ${\mathrm{Mn}}_3\left({\mathrm{Cu}}_{0.6}{\mathrm{Si}}_{0.15}{\mathrm{Ge}}_{0.25}\right)N$. This indicates that ${\mathrm{Mn}}_3\left({\mathrm{Cu}}_{0.6}{\mathrm{Si}}_{0.15}{\mathrm{Ge}}_{0.25}\right)N$ exhibits a spin glass state at low temperatures. We discussed the cause of spin glass behavior and correlated this spin glass behavior with broadening of the negative thermal expansion operation-temperature window of the manganese nitrides ${\mathrm{Mn}}_3\left({\mathrm{Cu}}_{0.6}{\mathrm{Si}}_{0.15}{\mathrm{Ge}}_{0.25}\right)N$.     

Chern–Simons formulation of three-dimensional gravity with torsion and nonmetricity

We consider various models of three-dimensional gravity with torsion or nonmetricity (metric affine gravity), and show that they can be written as Chern–Simons theories with suitable gauge groups. Using the groups $\mathrm{ISO}(2,1)$, $\mathrm{SL}(2,\mathbb{C})$ and $\mathrm{SL}(2,\mathbb{R})\times \mathrm{SL}(2,\mathbb{R})$, and the fact that they admit two independent coupling constants, we obtain the Mielke–Baekler model for zero, positive and negative effective cosmological constant respectively. Choosing $\mathrm{SO}(3,2)$ as the gauge group, one gets a generalization of conformal gravity that has zero torsion and only the trace part of the nonmetricity. This characterizes a Weyl structure. Finally, we present a new topological model of metric affine gravity in three dimensions arising from an $\mathrm{SL}(4,\mathbb{R})$ Chern–Simons theory.     

Effect upon universal order of Hubble expansion

The level of order $R$ in a spherical system of radius $r_0$ with a probability amplitude function $\psi \left(x\right),x=r,\theta ,?$ obeys $R=(1/2)r_0^{2}I$, where $I=4\int dx{\left|?\psi \right|}^2$ is its Fisher information level. We show that a flat space universe obeying the Robertson–Walker metric has an invariant value of the order as it undergoes either uniform Hubble expansion or contraction. This means that Hubble expansion per se does not cause a loss of universal order as time progresses. Instead, coarse graining processes characterizing decoherence and friction might cause a loss of order. Alternatively, looking backward in time, i.e. under Hubble contraction, as the big bang is approached and the Hubble radius $r_0$ approaches small values, the structure in the amplitude function $\psi \left(x\right)$ becomes ever more densely packed, increasing all local slopes $?\psi$ and causing the Fisher information $I$ to approach unboundedly large values. As a speculation, this ever-well locates the initial position of the universe in a larger, multiverse.     

Quantum point contact conductance in normal metal/insulator/ metal/dx2−y2+idxy mixed wave superconductor junctions

The tunneling conductance in a normal metal/insulator/metal/$d_{x^2?y^2}+i{d}_{xy}$ mixed wave superconductor (N/I/N/$d_{x^2?y^2}+i{d}_{xy}$) junction is calculated, where the N/I/N region is a quantum wire. It is found in the single-mode case that the magnitude of the tunneling conductance near zero voltage is enhanced due to the Andreev bound state by quasiparticles with perpendicular and horizontal injection, and the zero-bias conductance varies with $L$ ($L$ is the distance from insulating layer to the interface of N/$d_{x^2?y^2}+i{d}_{xy}$ mixed wave superconductor). Splitting of the zero-bias conductance peak appears in the quantum point contact tunneling spectra for an N/I/N/$d_{x^2?y^2}+i{d}_{xy}$ junction, and several subgap peaks can split at the same time. On increasing both $L$ and the magnitude ratio of the two components for the $d_{x^2?y^2}+i{d}_{xy}$ mixed wave, the subgap resonances exhibit an alternately high and low behavior inside the energy gap. These results are different from those in d-wave and p-wave superconductor junctions.     

Electric field and temperature dependence of hole mobility in electroluminescent PDY 132 polymer thin films

The current density–voltage ($J\text{–}V$) behavior of polymer PDY 132 thin films has been investigated in hole-only device configuration, viz., ITO/poly(ethylene-dioxthiophene):polystyrenesulphonate (PEDOT:PSS)/PDY 132/Au, as a function of polymer (PDY) film thickness (150 nm and 200 nm) and temperature (290–90 K). Hole current density was found to follow two distinct modes of conduction, (i) low electric field region I: ohmic conduction where slope $～1$, and (ii) intermediate and high electric field region II: non ohmic conduction where slope $～2$. Region I has been attributed to the transport of intrinsic background charge carriers while region II has been found to be governed by space charge limited currents (SCLC) with hole mobility strongly dependent on electric field and temperature. The respective hole transport parameters determined from the SCLC regime, ${\mu }_{p0}$ is $3.7\times 10^{?3}{m}^2/Vs$, ${\mu }_p(0,T)$ is $3.7\times 10^{?8}{m}^2/Vs$, and zero field activation energy (${\Delta }_0$) of 0.48 eV is obtained.