[en] Multiple Zhang-Rice type spectral features have been observed in resonant inelastic X-ray scattering (RIXS) from the quasi-one-dimensional cuprate charge transfer insulator Li₂CuO₂. The first feature appears at constant emission energy, and is associated with a Zhang-Rice singlet final state. The second is an interplaquette charge transfer excitation that results in a novel triplet Zhang-Rice-type final state. It is accompanied by the presence of a O 2p nonbonding to upper Hubbard band excitation at an energy close to that of a calculated triplet charge transfer Zhang-Rice-type excitation. The site selectivity and polarization rules associated with RIXS allows these two excitations to be distinguished

[en] We report the evolution of structural, magnetic and dielectric properties due to the partial substitution of Ba by Sr in the high-temperature multiferroic YBaCuFeO₅. This compound exhibits ferroelectric and antiferromagnetic transitions around 200 K and these two phenomena are presumed to be coupled with each other. Our studies on magnetic and dielectric properties of the ${\text{YBa}}_{1-<!--\; ???\; -->x}{\text{Sr}}_x{\text{CuFeO}}_5$ ($x=0.0$, 0.25 and 0.5) show that the substitution of Sr shifts the magnetic transition towards higher temperature, whereas the dielectric transition to lower temperature. These results indicate that the magnetic and dielectric transitions might not be interrelated in the Sr-substituted YBaCuFeO₅. The nature of magnetodielectric coupling changes across the series with the presence of higher-order coupling terms. Additionally, in these compounds glassy dynamics of electric dipoles is observed at low temperatures. (letter)

[en] The electrocaloric effect in PbTiO₃ ferroelectric nanoparticles has been studied using Landau-Ginzburg-Devonshire theory to determine the optimal electric field to induce large adiabatic temperature changes. The calculation results show that a large positive $(\mathrm{\Delta <!--\; ??\; -->}T=6.2\text{K})$ or negative $(\mathrm{\Delta <!--\; ??\; -->}T=-<!--\; ???\; -->5.7\text{K})$ adiabatic temperature change could be induced using an inhomogeneous electric field. The electrically induced negative adiabatic temperature change becomes positive as the strength of the electric field is increased. This transformation of the adiabatic temperature change is attributed to domain switching owing to the applied electric field. These results may provide an explanation for transformations from a negative to a positive electrocaloric effect in ferroelectrics. (letter)

[en] We study the one-photon scattering problem for a super-cavity (SC) coupling with two two-level atoms. With atomic decay, photon reflection shows a sudden drop at $\mathrm{\Delta <!--\; ??\; -->}=0$ only for the two atoms in the node-antinode configuration. The underlying mechanism is attributed to the fact that the scatterer has a configuration-dependent localized dissipated eigen-mode at $\mathrm{\Delta <!--\; ??\; -->}=0$. In the node-antinode configuration, the eigen-mode localized at the input side, through which the photon can enter into the SC, then excites the atom at the node and finally leaks into the reservoir due to atomic decay. In this way, a sudden drop emerges at $\mathrm{\Delta <!--\; ??\; -->}=0$ in photon reflection. In the antinode-node case, however, the eigen-mode is localized at the output side, so the photon is completely reflected at $\mathrm{\Delta <!--\; ??\; -->}=0$. A similar phenomenon has been observed in a recent experiment of X-ray quantum optics (Röhlsberger R. et al., Nature, 482 (2012) 199) but with a complicated explanation due to electromagnetically induced transparency. (letter)

[en] We investigate the collective dynamics of bi-stable elements connected in different network topologies, ranging from rings and small-world networks, to random and deterministic scale-free networks. We focus on the correlation between network properties and global stability measures of the synchronized state, in particular the average critical coupling strength $⟨<!--\; ???\; -->{\mathrm{ϵ<!--\; ??\; -->}}_c⟩<!--\; ???\; -->$ yielding transition to synchronization. Further, we estimate the robustness of the synchronized state by finding the minimal fraction of nodes f _c that need to be perturbed in order to lose synchronization. Our central result from these synchronization features is the following: while networks properties can provide indicators of synchronization within a network class, they fail to provide consistent indicators across network classes. For instance, the heterogeneity of degree does not consistently impact synchronization, as is evident through the stark difference in the synchronizability of rings vis-à-vis small-world and star networks, all of which have same average degree and deviation around the mean degree in the limit of large networks. Further we demonstrate that clustering coefficient is also not a consistent feature in determining synchronization. This is clear through the similarity of synchronization properties in rings with significantly different clustering coefficients, and the striking difference in synchronization of a star network and a ring having the same clustering coefficient. Even the characteristic path length, which is of paramount importance in determining synchronization, does not provide a one-to-one correspondence with synchronization properties across classes. Namely, synchronization is significantly favoured in networks with low path lengths within a network class. However, the same characteristic path length in different types of networks yields very different $⟨<!--\; ???\; -->{\mathrm{ϵ<!--\; ??\; -->}}_c⟩<!--\; ???\; -->$ and f _c. (letter)

[en] The Dirac equation in curved space is used to study the optical transmittance of deformed graphene along a given direction. Our theoretical analysis of the available experimental data for the light transmittance suggests that the periodic ripple associated with the out-of-plane deformation observed in unstrained graphene explains the observations. Furthermore, the experimental uniaxial strained graphene for light transmittance shows two features, namely the modification of the ${\cos }^2<!--\; ???\; -->\mathrm{\theta <!--\; ??\; -->}$ law and the decrease of the amplitude of the oscillations with the polarization angle θ, which can be well accommodated within the theoretical analysis used here and provide further evidence of the validity of using QFT in curved space to understand two-dimensional materials. (letter)

[en] Here, we report the dielectric, impedance and transport studies of non-charge-ordered magnetic glass, Tb_0.5Sr_0.5MnO₃ single crystals. The temperature- and frequency-dependent real $({\mathrm{ϵ<!--\; ??\; -->}}^{\prime })$ and imaginary (${\mathrm{ϵ<!--\; ??\; -->}}^{″}$ or tanδ) parts of the dielectric constant display large frequency dispersion. The colossal dielectric constant observed $(\approx <!--\; ???\; -->3000)$ above 100 K is considered extrinsic. The activation energy of thermally activated relaxation is calculated using the Arrhenius law. Interestingly, two relaxation regions, each with different activation energies (E _a) are clearly evident, one occurring above and the other below the glassy magnetic transition temperature $(T_g=44\text{K})$. E _a relates to the electron hopping between Mn³⁺ and Mn⁴⁺ ions and the origin of dielectric dispersion. E _a in the glassy region is lower than that in paramagnetic region due to a lower energy spent in hopping between frozen spins. Bulk capacitance and resistivity derived from impedance measurements reveal anomalies around T _g. Electrical transport data between 60 and 300 K shows insulating behavior and the calculated E _a is in good agreement with the value obtained from dielectric measurements. Although, these results cannot be interpreted in terms of magneto-electric coupling, the correlation observed between magnetic and electronic states of the system is significant. (letter)

[en] An innovative diamond detector layout is presented that is designed to operate at high temperature under intense neutron and gamma fluxes. It is made of a 500 μm “electronic grade” diamond film with 100 nm thick Ag metal contacts deposited onto each surface of the film by means of thermal evaporation. A $2\mathrm{\mu <!--\; ??\; -->}\text{m}$ thick layer of ⁶LiF has been deposited on top of one of the two Ag contacts to make the detector sensitive to thermal neutrons. The device was tested at the ISIS spallation neutron source (Rutherford Appleton Laboratory, UK) using the INES beam line. The detector was continuously irradiated for 100 hours in vacuum $(p={10}^{-<!--\; ???\; -->5}\text{mbar})$, exposed to a neutron flux of about 10⁶ n cm⁻² s⁻¹ at a temperature $T=150{}^{\circ <!--\; ???\; -->}\text{C}$. The aim of this experiment was to study the time dependence of the diamond detector performance while operating at high temperature under irradiation, providing a first experimental proof of reliable continuous operation for 100 hours at high temperature in a harsh environment. (letter)

[en] In this paper, a theoretical study of 1, 2-dimethoxy ethane (DXE) and ${\text{K}}^{+}/{\text{Li}}^{+}$ binary mixture in low-temperature plasmas is reported. The most probable reactions of alkali metal ions K⁺ and Li⁺ with dimethoxy ethane molecule and its fragment ions are selected in order to obtain appropriate gas phase enthalpies of formation for the products. The scattering cross-sections set as a function of kinetic energy and transport parameters as a function of E/N (E is the electric field, N the gas density) were obtained by using the Monte Carlo technique. (letter)

[en] We studied the suppression of the weak antilocalization (WAL) effect and the dependence of spin dynamics for a two-dimensional electron gas in the inversion layers of two different Hg_1−xCd_xTe samples in the presence of in-plane magnetic field $(B_{//})$. The WAL magnetoconductance is fitted by the Golub model to acquire the variations of phase coherence time with increasing $B_{//}$. The effective g-factors in the form of $|m_r^{\ast <!--\; ???\; -->}{g}^{\ast <!--\; ???\; -->}|$ ($m_r^{\ast <!--\; ???\; -->}$ is the relative effective mass) at zero magnetic field and high magnetic field are obtained by investigating the electron dephasing with varying $B_{//}$ and measuring the spin splitting of the Shubnikov-de Hass oscillations, respectively. As the obtained g-factors are in accordance with the reported results, the suppression of the WAL effect can be attributed to the competition between Zeeman splitting and spin-orbit interaction rather than to the microroughness scattering. (letter)