Structural determination and electronic properties of 4d perovskite SrPdO3

The structure and ground state electronic structure of the recently synthesized SrPdO$_3$ perovskite [A. Galal {\em et al.}, J. Power Sources, {\bf 195}, 3806 (2010)] have been studied by means of screened hybrid functional and the GW approximation with the inclusion of electron-hole interaction within the test-charge/test-charge scheme. By conducting a structural search based on lattice dynamics and group theoretical method we identify the orthorhombic phase with $P_{nma}$ space group as the most stable crystal structure. The phase transition from the ideal cubic perovskite structure to the $P_{nma}$ one is explained in terms of the simultaneous stabilization of the antiferrodistortive phonon modes $R_4^+$ and $M_3^+$. Our results indicate that SrPdO$_3$ exhibits an insulating ground state, substantiated by a GW$_0$ gap of about 1.1 eV. Spin polarized calculations suggests that SrPdO$_3$ adopts a low spin state ($t_{2g}^{\uparrow\downarrow\uparrow\downarrow\uparrow\downarrow}e_g^0$), and is expected to exhibit spin excitations and spin state crossovers at finite temperature, analogous to the case of 3$d$ isoelectronic LaCoO$_3$. This would provide a new playground for the study of spin state transitions in 4$d$ oxides and new opportunity to design multifunctional materials based on 4$d$ $P_{nma}$ building block

Time changes of symmetric diffusions and Feller measures

We extend the classical Douglas integral, which expresses the Dirichlet integral of a harmonic function on the unit disk in terms of its value on boundary, to the case of conservative symmetric diffusion in terms of Feller measure, by using the approach of time change of Markov processes.Comment: Published at http://dx.doi.org/10.1214/009117904000000649 in the Annals of Probability (http://www.imstat.org/aop/) by the Institute of Mathematical Statistics (http://www.imstat.org

Scatterer induced mode splitting in poly(dimethylsiloxane) coated microresonators

We investigate scatterer induced mode splitting in a composite microtoroidal resonator (Q ~ 10^6) fabricated by coating a silica microtoroid (Q ~ 10^7) with a thin poly(dimethylsiloxane) layer. We show that the two split modes in both coated and uncoated silica microtoroids respond in the same way to the changes in the environmental temperature. This provides a self-referencing scheme which is robust to temperature perturbations. Together with the versatile functionalities of polymer materials, mode splitting in polymer and polymer coated microresonators offers an attractive sensing platform that is robust to thermal noise.Comment: 9 pages, 3 figures, 15 reference

Estimation of Purcell factor from mode-splitting spectra in an optical microcavity

We investigate scattering process in an ultra-high-Q optical microcavity coupled to subwavelength scatterers by introducing "splitting quality" Qsp, a dimensionless parameter defined as the ratio of the scatterer-induced mode splitting to the total loss of the coupled system. A simple relation is introduced to directly estimate the Purcell factor from single-shot measurement of transmission spectrum of scatterer-coupled cavity. Experiments with polystyrene (PS) and gold (Au) nanoparticles, Erbium ions and Influenza A virions show that Purcell-factor-enhanced preferential funneling of scattering into the cavity mode takes place regardless of the scatterer type. Experimentally determined highest Qsp for single PS and Au nanoparticles are 9.4 and 16.19 corresponding to Purcell factors with lower bounds of 353 and 1049, respectively. The highest observed Qsp was 31.2 for an ensemble of Au particles. These values are the highest Qsp and Purcell factors reported up to date.Comment: 5 Pages, 4 Figures, 12 Reference

Regional Finance and Regional Disparities in China

China’s growth has been spectacularly high and persistent over the last few decades. However, there have been regular expressions of concern about the uneven distribution of the benefits across regions and, at times, it has been asserted that the regional distribution of available investment funds has played an important role – national financial institutions (mainly state-owned banks) have redirected deposits from the inland to loans to large institutions in the more prosperous coastal regions. At the same time, smaller regionally-focussed institutions are likely to improve the distribution of funds. We use a panel data set disaggregated by province for the years 1986 to 2004 to test these propositions. We employ recent panel unit roots and cointegration tests using data for state-owned bank loans as well as loans by rural credit cooperatives. We find that financial disparities are related to output disparities, that this relationship is positive, that it is stronger for rural credit cooperatives than for state-owned banks and that this relationship is causal in both the long and short runs. A reduction in financial disparities can be expected to lead a narrowing of output disparities in the short run and in the long run with the effect being larger for rural credit cooperatives than for state-owned commercial banks.regional disparities, panel econometrics, regional finance, China

Hierarchy of Exchange-correlation Functionals in Computing Lattice thermal conductivities of rocksalt and zinc-blende semiconductors

Lattice thermal conductivity (L) is a crucial characteristic of crystalline solids with significant implications for thermal management, energy conversion, and thermal barrier coating. The advancement of computational tools based on density functional theory (DFT) has enabled the effective utilization of phonon quasiparticle-based approaches to unravel the underlying physics of various crystalline systems. While the higher order of anharmonicity is commonly used for explaining extraordinary heat transfer behaviors in crystals, the impact of exchange-correlation (XC) functionals in DFT on describing anharmonicity has been largely overlooked. The XC functional is essential for determining the accuracy of DFT in describing interactions among electrons/ions in solids and molecules. However, most XC functionals in solid-state physics are primarily focused on computing the properties that only require small atomic displacements from the equilibrium (within the harmonic approximation), such as harmonic phonons and elastic constants, while anharmonicity involves larger atomic displacements. Therefore, it is more challenging for XC functionals to accurately describe atomic interactions at the anharmonicity level. In this study, we systematically investigate the room-temperature L of 16 binary compounds with rocksalt and zinc-blende structures using various XC functionals such as local density approximation (LDA), Perdew-Burke-Ernzerhof (PBE), revised PBE for solid and surface (PBEsol), optimized B86b functional (optB86b), revised Tao-Perdew-Staroverov-Scuseria (revTPSS), strongly constrained and appropriately normed functional (SCAN), regularized SCAN (rSCAN), and regularized-restored SCAN (r2⁢SCAN) in combination with different perturbation orders, including phonon within harmonic approximation (HA) plus three-phonon scattering (HA+3⁢ph), phonon calculated using self-consistent phonon theory (SCPH) plus three-phonon scattering (SCPH + 3ph), and SCPH phonon plus three- and four-phonon scattering (SCPH + 3,4ph). Our results show that the XC functional exhibits strong entanglement with perturbation order and the mean relative absolute error (MRAE) of the computed L is strongly influenced by both the XC functional and perturbation order, leading to error cancellation or amplification. The minimal (maximal) MRAE is achieved with revTPSS (rSCAN) at the HA + 3ph level, SCAN (r2⁢SCAN) at the SCPH + 3ph level, and PBEsol (rSCAN) at the SCPH + 3,4ph level. Among these functionals, PBEsol exhibits the highest accuracy at the highest perturbation order. The SCAN-related functionals demonstrate moderate accuracy but are suffer from numerical instability and high computational costs. Furthermore, the different impacts of quartic anharmonicity on L in rocksalt and zinc-blende structures are identified by all XC functionals, attributed to the distinct lattice anharmonicity in these two structures. These findings serve as a valuable reference for selecting appropriate functionals for describing anharmonic phonons and offer insights into high-order force constant calculations that could facilitate the development of more accurate XC functionals for solid materials