Frozen photons in Jaynes Cummings arrays

We study the origin of "frozen" states in coupled Jaynes-Cummings-Hubbard arrays in the presence of losses. For the case of half the array initially populated with photons while the other half is left empty we show the emergence of self-localized photon or "frozen" states for specific values of the local atom-photon coupling. We analyze the dynamics in the quantum regime and discover important additional features appear not captured by a semiclassical treatment, which we analyze for different array sizes and filling fractions. We trace the origin of this interaction-induced photon "freezing" to the suppression of excitation of propagating modes in the system at large interaction strengths. We discuss in detail the possibility to experimentally probe the relevant transition by analyzing the emitted photon correlations. We find a strong signature of the effect in the emitted photons statistics

Study of Nd-Fe-B Alloys with Nonstoichiometric Nd Content in Optimal Magnetic State

Characterization of two rapid-quenched Nd-Fe-B alloys with nonstoichiometric Nd content in the optimized magnetic state was carried out using the X-ray diffractometry (XRD), (57)Fe Mossbauer spectroscopic phase analysis (MS), electron microscopy (TEM), high resolution TEM (HREM) and Superconducting Quantum Interference Device (SQUID) magnetometer. The experimental results demonstrate the fundamental difference in the structure and magnetic properties of the two investigated alloys in the optimized magnetic state. The Nd-Fe-B alloy with the reduced Nd content (Nd(4.5)Fe(77)B(18.5)) was found to have the nanocomposite structure of Fe(3)B/Nd(2)Fe(14)B and partly alpha-Fe/Nd(2)Fe(14)B, with mean grain size below 30 nm. On the other side, the overstoichiometric Nd(14)Fe(79)B(7) alloy has almost a monophase structure with the dominant content of the hard magnetic phase Nd(2)Fe(14)B (up to 95 wt. %) and a mean crystallite size about 60 nm, as determined by XRD and TEM analysis. The results of magnetic measurements on SQUID magnetometer also suggest the nanocomposite structure of the Nd-low alloy and nanocrystalline decoupled structure of the Nd-rich alloy after the optimal heat treatment.open

Non-equilibrium supercurrent through mesoscopic ferromagnetic weak links

We consider a mesoscopic normal metal, where the spin degeneracy is lifted by a ferromagnetic exchange field or Zeeman splitting, coupled to two superconducting reservoirs. As a function of the exchange field or the distance between the reservoirs, the supercurrent through this device oscillates with an exponentially decreasing envelope. This phenomenon is similar to the tuning of a supercurrent by a non-equilibrium quasiparticle distribution between two voltage-biased reservoirs. We propose a device combining the exchange field and non-equilibrium effects, which allows us to observe a range of novel phenomena. For instance, part of the field-suppressed supercurrent can be recovered by a voltage between the additional probes.Comment: 7 pages, 8 figures, Europhys. Lett., to be published, corrected two reference

Electron Impact Ionization Close to the Threshold: Classical Calculations

In this paper we present Classical Trajectory Monte Carlo (CTMC) calculations for single and multiple electron ionization of Argon atoms and ions in the threshold region. We are able to recover the Wannier exponents a for the power-law behavior of the cross section s versus excess energy: the exact value of the exponent as well as the existence of its saturation for multiple ionization appear to be related to how the total binding energy is shared between target electrons.Comment: 9 pages. To be published in Journal of Physics

Non-equilibrium many-body effects in driven nonlinear resonator arrays

We study the non-equilibrium behavior of optically driven dissipative coupled resonator arrays. Assuming each resonator is coupled with a two-level system via a Jaynes-Cummings interaction, we calculate the many-body steady state behavior of the system under coherent pumping and dissipation. We propose and analyze the many-body phases using experimentally accessible quantities such as the total excitation number, the emitted photon spectra and photon coherence functions for different parameter regimes. In parallel, we also compare and contrast the expected behavior of this system assuming the local nonlinearity in the cavities is generated by a generic Kerr effect rather than a Jaynes-Cummings interaction. We find that the behavior of the experimentally accessible observables produced by the two models differs for realistic regimes of interactions even when the corresponding nonlinearities are of similar strength. We analyze in detail the extra features available in the Jaynes-Cummings-Hubbard (JCH) model originating from the mixed nature of the excitations and investigate the regimes where the Kerr approximation would faithfully match the JCH physics. We find that the latter is true for values of the light-matter coupling and losses beyond the reach of current technology. Throughout the study we operate in the weak pumping, fully quantum mechanical regime where approaches such as mean field theory fail, and instead use a combination of quantum trajectories and the time evolving block decimation algorithm to compute the relevant steady state observables. In our study we have assumed small to medium size arrays (from 3 up to 16 sites) and values of the ratio of coupling to dissipation rate $g/\gamma \sim 20$ which makes our results implementable with current designs in Circuit QED and with near future photonic crystal set ups.Comment: 22 pages, 6 figure

Transition from reciprocal cooperation to persistent behaviour in social dilemmas at the end of adolescence.

While human societies are extraordinarily cooperative in comparison with other social species, the question of why we cooperate with unrelated individuals remains open. Here we report results of a lab-in-the-field experiment with people of different ages in a social dilemma. We find that the average amount of cooperativeness is independent of age except for the elderly, who cooperate more, and a behavioural transition from reciprocal, but more volatile behaviour to more persistent actions towards the end of adolescence. Although all ages react to the cooperation received in the previous round, young teenagers mostly respond to what they see in their neighbourhood regardless of their previous actions. Decisions then become more predictable through midlife, when the act of cooperating or not is more likely to be repeated. Our results show that mechanisms such as reciprocity, which is based on reacting to previous actions, may promote cooperation in general, but its influence can be hindered by the fluctuating behaviour in the case of children

Threshold detachment of negative ions by electron impact

The description of threshold fragmentation under long range repulsive forces is presented. The dominant energy dependence near threshold is isolated by decomposing the cross section into a product of a back ground part and a barrier penetration probability resulting from the repulsive Coulomb interaction. This tunneling probability contains the dominant energy variation and it can be calculated analytically based on the same principles as Wannier's description for threshold ionization under attractive forces. Good agreement is found with the available experimental cross sections on detachment by electron impact from $D^{-}$, $O^{-}$ and $B^{-}$.Comment: 4 pages, 4 figures (EPS), to appear in Phys.Rev.Lett, Feb. 22nd, 199

Energy Metabolism in Uncoupling Protein 3 Gene Knockout Mice

Uncoupling protein 3 (UCP3) is a member of the mitochondrial anion carrier superfamily. Based upon its high homology with UCP1 and its restricted tissue distribution to skeletal muscle and brown adipose tissue, UCP3 has been suggested to play important roles in regulating energy expenditure, body weight, and thermoregulation. Other postulated roles for UCP3 include regulation of fatty acid metabolism, adaptive responses to acute exercise and starvation, and prevention of reactive oxygen species (ROS) formation. To address these questions, we have generated mice lacking UCP3 (UCP3 knockout (KO) mice). Here, we provide evidence that skeletal muscle mitochondria lacking UCP3 are more coupled (i.e. increased state 3/state 4 ratio), indicating that UCP3 has uncoupling activity. In addition, production of ROS is increased in mitochondria lacking UCP3. This study demonstrates that UCP3 has uncoupling activity and that its absence may lead to increased production of ROS. Despite these effects on mitochondrial function, UCP3 does not seem to be required for body weight regulation, exercise tolerance, fatty acid oxidation, or cold-induced thermogenesis. The absence of such phenotypes in UCP3 KO mice could not be attributed to up-regulation of other UCP mRNAs. However, alternative compensatory mechanisms cannot be excluded. The consequence of increased mitochondrial coupling in UCP3 KO mice on metabolism and the possible role of yet unidentified compensatory mechanisms, remains to be determined

Energy Metabolism in Uncoupling Protein 3 Gene Knockout Mice

Uncoupling protein 3 (UCP3) is a member of the mitochondrial anion carrier superfamily. Based upon its high homology with UCP1 and its restricted tissue distribution to skeletal muscle and brown adipose tissue, UCP3 has been suggested to play important roles in regulating energy expenditure, body weight, and thermoregulation. Other postulated roles for UCP3 include regulation of fatty acid metabolism, adaptive responses to acute exercise and starvation, and prevention of reactive oxygen species (ROS) formation. To address these questions, we have generated mice lacking UCP3 (UCP3 knockout (KO) mice). Here, we provide evidence that skeletal muscle mitochondria lacking UCP3 are more coupled (i.e. increased state 3/state 4 ratio), indicating that UCP3 has uncoupling activity. In addition, production of ROS is increased in mitochondria lacking UCP3. This study demonstrates that UCP3 has uncoupling activity and that its absence may lead to increased production of ROS. Despite these effects on mitochondrial function, UCP3 does not seem to be required for body weight regulation, exercise tolerance, fatty acid oxidation, or cold-induced thermogenesis. The absence of such phenotypes in UCP3 KO mice could not be attributed to up-regulation of other UCP mRNAs. However, alternative compensatory mechanisms cannot be excluded. The consequence of increased mitochondrial coupling in UCP3 KO mice on metabolism and the possible role of yet unidentified compensatory mechanisms, remains to be determined