Charge and spin fractionalization in strongly correlated topological insulators

We construct an effective topological Landau-Ginzburg theory that describes general SU(2) incompressible quantum liquids of strongly correlated particles in two spatial dimensions. This theory characterizes the fractionalization of quasiparticle quantum numbers and statistics in relation to the topological ground-state symmetries, and generalizes the Chern-Simons, BF and hierarchical effective gauge theories to an arbitrary representation of the SU(2) symmetry group. Our main focus are fractional topological insulators with time-reversal symmetry, which are treated as generalizations of the SU(2) quantum Hall effect.Comment: 8 pages, published versio

Influencing Factors on the Dielectric Breakdown Strength in F-gas Free High-voltage Switchgear

After being in the focus of sciences' and industry's research and development activities for many years, the investigation of possible SF6 gas-alternatives has been even more intensified after the revision of the European regulation on fluorinated gases in 2014. In this contribution the influencing factors on the dielectric breakdown of clean air are investigated for weak inhomogeneous field and gas pressures up to 10 bar. Modelling approaches and experimental data are compared

Switching Behaviour of a Series Connection of a Vacuum Interrupter and a Gas Circuit Breaker

After being in the focus of sciences' and industry's research and development activities for many years, the investigation of possible SF6 gas-alternatives has been even more intensified after the revision of the European F-Gas regulation 517/2014. As natural gases yield a significantly lower dielectric strength in comparison to SF6, new challenges arise for the design of high voltage switchgear. Vacuum interrupters are environmentally friendly, reliable and able to withstand steep rising transient recovery voltages. In the last years, first installations of switchgear based on vacuum switching technology in sub-transmission level are in operation. One option for the realization of a SF6 free high voltage switchgear for transmission level is the combination of a gas circuit breaker filled with an atmospheric gas with a vacuum interrupter in a hybrid switchgear. In this contribution the voltage distribution and switching behavior of a hybrid circuit breaker is experimentally investigated

Electrical current-driven pinhole formation and insulator-metal transition in tunnel junctions

Current Induced Resistance Switching (CIS) was recently observed in thin tunnel junctions (TJs) with ferromagnetic (FM) electrodes and attributed to electromigration of metallic atoms in nanoconstrictions in the insulating barrier. The CIS effect is here studied in TJs with two thin (20 \AA) non-magnetic (NM) Ta electrodes inserted above and below the insulating barrier. We observe resistance (R) switching for positive applied electrical current (flowing from the bottom to the top lead), characterized by a continuous resistance decrease and associated with current-driven displacement of metallic ions from the bottom electrode into the barrier (thin barrier state). For negative currents, displaced ions return into their initial positions in the electrode and the electrical resistance gradually increases (thick barrier state). We measured the temperature (T) dependence of the electrical resistance of both thin- and thick-barrier states ($R_b$ and R$_B$ respectively). Experiments showed a weaker R(T) variation when the tunnel junction is in the $R_b$ state, associated with a smaller tunnel contribution. By applying large enough electrical currents we induced large irreversible R-decreases in the studied TJs, associated with barrier degradation. We then monitored the evolution of the R(T) dependence for different stages of barrier degradation. In particular, we observed a smooth transition from tunnel- to metallic-dominated transport. The initial degradation-stages are related to irreversible barrier thickness decreases (without the formation of pinholes). Only for later barrier degradation stages do we have the appearance of metallic paths between the two electrodes that, however, do not lead to metallic dominated transport for small enough pinhole radius.Comment: 10 pages, 3 figure

Magnetic susceptibility and specific heat of the spin-1/2 Heisenberg model on the kagome lattice and experimental data on ZnCu3(OH)6Cl2

We compute the magnetic susceptibility and specific heat of the spin-1/2 Heisenberg model on the kagome lattice with high-temperature expansions and exact diagonalizations. We compare the results with the experimental data on ZnCu3(OH)6Cl2 obtained by Helton et al. [Phys. Rev. Lett. 98, 107204 (2007)]. Down to k_BT/J~0.2, our calculations reproduce accurately the experimental susceptibility, with an exchange interaction J~190K and a contribution of 3.7% of weakly interacting impurity spins. The comparison between our calculations of the specific heat and the experiments indicate that the low-temperature entropy (below ~20K) is smaller in ZnCu3(OH)6Cl2 than in the kagome Heisenberg model, a likely signature of other interactions in the system.Comment: Minor revisions in the text and references. To appear in Eur. Phys. J.

Altilix\uae Supplement Containing Chlorogenic Acid and Luteolin Improved Hepatic and Cardiometabolic Parameters in Subjects with Metabolic Syndrome: A 6 Month Randomized, Double-Blind, Placebo-Controlled Study

The objective was to evaluate the eects of 6 months of supplementation with Altilix\uae, containing chlorogenic acid and its derivatives, and luteolin and its derivatives, on cardiovascular risk and hepatic markers in subjects with metabolic syndrome (MetS). A randomized, double-blind, placebo-controlled study was performed in 100 subjects with MetS with a follow-up period of 6 months; 50 subjects were randomized to Altilix\uae (26 men and 24 women, mean age 63 8 years) and the other 50 to placebo (28 men and 22 women, mean age 63 11 years). Anthropometric, cardiometabolic, and hepatic parameters were assessed at baseline and at the end of follow-up. Carotid intima-media thickness and endothelial function were assessed by doppler ultrasound and by flow-mediated dilation of the brachial artery, respectively. The presence and degree of non-alcoholic fatty liver disease (NAFLD) was assessed by the fatty liver index (FLI), and subjects were divided into three subgroups: (1) without NAFLD; (2) with borderline NAFLD; and (3) with NAFLD. After 6 months of Altilix\uae supplementation, we found a significant improvement vs. placebo in most of the evaluated parameters, including body weight (2.40% (95% CI 3.79, 1.01); p < 0.001), waist circumference (2.76% (95% CI 4.55, 0.96); p = 0.003), HbA1c (0.95% (95% CI 1.22, 0.67); p < 0.001), plasma lipids, FLI (21.83% (95% CI 27.39, 16.27); p < 0.001), hepatic transaminases, flow-mediated dilation (10.56% (95% CI 5.00, 16.12); p < 0.001), and carotid intima-media thickness (39.48% (95% CI 47.98, 30.97); p < 0.001). Further, the improvement in cardiometabolic variables was independent of the degree of hepatic steatosis. Altilix\uae supplementation improved hepatic and cardio-metabolic parameters in MetS subjects. Altilix\uae supplementation was a beneficial approach in the management of hepatic and cardiometabolic alterations in MetS subjects

General Relativity as Classical Limit of Evolutionary Quantum Gravity

We analyze the dynamics of the gravitational field when the covariance is restricted to a synchronous gauge. In the spirit of the Noether theorem, we determine the conservation law associated to the Lagrangian invariance and we outline that a non-vanishing behavior of the Hamiltonian comes out. We then interpret such resulting non-zero ``energy'' of the gravitational field in terms of a dust fluid. This new matter contribution is co-moving to the slicing and it accounts for the ``materialization'' of a synchronous reference from the corresponding gauge condition. Further, we analyze the quantum dynamics of a generic inhomogeneous Universe as described by this evolutionary scheme, asymptotically to the singularity. We show how the phenomenology of such a model overlaps the corresponding Wheeler-DeWitt picture. Finally, we study the possibility of a Schr\"odinger dynamics of the gravitational field as a consequence of the correspondence inferred between the ensemble dynamics of stochastic systems and the WKB limit of their quantum evolution. We demonstrate that the time dependence of the ensemble distribution is associated with the first order correction in $\hbar$ to the WKB expansion of the energy spectrum.Comment: 23 pages, to appear on Class. Quant. Gra

Low temperature vortex liquid in La2−xSrxCuO4\rm La_{2-x}Sr_xCuO_4

In the cuprates, the lightly-doped region is of major interest because superconductivity, antiferromagnetism, and the pseudogap state \cite{Timusk,Lee,Anderson} come together near a critical doping value $x_c$. These states are deeply influenced by phase fluctuations \cite{Emery} which lead to a vortex-liquid state that surrounds the superconducting region \cite{WangPRB01,WangPRB06}. However, many questions \cite{Doniach,Fisher,FisherLee,Tesanovic,Sachdev} related to the nature of the transition and vortex-liquid state at very low tempera- tures $T$ remain open because the diamagnetic signal is difficult to resolve in this region. Here, we report torque magnetometry results on $\rm La_{2-x}Sr_xCuO_4$ (LSCO) which show that superconductivity is lost at $x_c$ by quantum phase fluctuations. We find that, in a magnetic field $H$, the vortex solid-to-liquid transition occurs at field $H_m$ much lower than the depairing field $H_{c2}$. The vortex liquid exists in the large field interval $H_m \ll H_{c2}$, even in the limit $T\to$0. The resulting phase diagram reveals the large fraction of the $x$-$H$ plane occupied by the quantum vortex liquid.Comment: 6 pages, 4 figures, submitted to Nature Physic

Magnetic fields in galaxies: I. Radio disks in local late-type galaxies

We develop an analytical model to follow the cosmological evolution of magnetic fields in disk galaxies. Our assumption is that fields are amplified from a small seed field via magnetohydrodynamical (MHD) turbulence. We further assume that this process is fast compared to other relevant timescales, and occurs principally in the cold disk gas. We follow the turbulent energy density using the Shabala & Alexander (2009) galaxy formation and evolution model. Three processes are important to the turbulent energy budget: infall of cool gas onto the disk and supernova feedback increase the turbulence; while star formation removes gas and hence turbulent energy from the cold gas. Finally, we assume that field energy is continuously transferred from the incoherent random field into an ordered field by differential galactic rotation. Model predictions are compared with observations of local late type galaxies by Fitt & Alexander (1993) and Shabala et al. (2008). The model reproduces observed magnetic field strengths and luminosities in low and intermediate-mass galaxies. These quantities are overpredicted in the most massive hosts, suggesting that inclusion of gas ejection by powerful AGNs is necessary in order to quench gas cooling and reconcile the predicted and observed magnetic field strengths.Comment: 10 pages, 8 figures; MNRAS in pres