374 research outputs found
Role of Orbital Degeneracy in Double Exchange Systems
We investigate the role of orbital degeneracy in the double exchange (DE)
model. In the limit, an effective generalized ``Hubbard''
model incorporating orbital pseudospin degrees of freedom is derived. The model
possesses an exact solution in one- and in infinite dimensions. In 1D, the
metallic phase off ``half-filling'' is a Luttinger liquid with
pseudospin-charge separation. Using the solution for our effective
model, we show how many experimental observations for the well-doped () three-dimensional manganites can be qualitatively
explained by invoking the role of orbital degeneracy in the DE model.Comment: 8 pages, 2 figures, submitted to Phys. Rev.
Transition between two ferromagnetic states driven by orbital ordering in La_{0.88}Sr_{0.12}MnO_3
A lightly doped perovskite mangantite La_{0.88}Sr_{0.12}MnO_3 exhibits a
phase transition at T_{OO}=145 K from a ferromagnetic metal (T_C=172 K) to a
novel ferromagnetic insulator.We identify that the key parameter in the
transition is the orbital degree of freedom in e_g electrons. By utilizing the
resonant x-ray scattering technique, orbital ordering is directly detected
below T_{OO}, in spite of a significant diminution of the cooperative
Jahn-Teller distortion. The new experimental features are well described by a
theory treating the orbital degree of freedom under strong electron
correlation. The present experimental and theoretical studies uncover a crucial
role of the orbital degree in the metal-insulator transition in lightly doped
manganites.Comment: 4 pages, 4 figure
Phase Transition in Perovskite Manganites with Orbital Degree of Freedom
Roles of orbital degree of freedom of Mn ions in phase transition as a
function of temperature and hole concentration in perovskite manganites are
studied. It is shown that the orbital order-disorder transition is of the first
order in the wide region of hole concentration and the Nel
temperature for the anisotropic spin ordering, such as the layer-type
antiferromagnetic one, is lower than the orbital ordering temperature due to
the anisotropy in the orbital space. The calculated results of the temperature
dependence of the spin and orbital order parameters explain a variety of the
experiments observed in manganites.Comment: 10 pages, 5 figure
Strain effect on electronic transport and ferromagnetic transition temperature in LaSrMnO thin films
We report on a systematic study of strain effects on the transport properties
and the ferromagnetic transition temperature of high-quality
LaSrMnO thin films epitaxially grown on (100) SrTiO
substrates. Both the magnetization and the resistivity are critically dependent
on the film thickness. is enhanced with decreasing the film thickness
due to the compressive stain produced by lattice mismatch. The resistivity
above 165 K of the films with various thicknesses is consistent with small
polaronic hopping conductivity. The polaronic formation energy is
reduced with the decrease of film thickness. We found that the strain
dependence of mainly results from the strain-induced electron-phonon
coupling. The strain effect on is in good agreement with the
theoretical predictions.Comment: 6 pages and 5 figures, accepted for publication in Phys. Rev.
Structural analysis of the Ss sialoglycoprotein specific for Henshaw blood group from human erythrocyte membranes
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/66122/1/j.1432-1033.1984.tb08155.x.pd
State owned enterprises as bribe payers: the role of institutional environment
Our paper draws attention to a neglected channel of corruptionâthe bribe payments by state-owned enterprises (SOEs). This is an important phenomenon as bribe payments by SOEs fruitlessly waste national resources, compromising public welfare and national prosperity. Using a large dataset of 30,249 firms from 50 countries, we show that, in general, SOEs are less likely to pay bribes for achieving organizational objectives owing to their political connectivity. However, in deteriorated institutional environments, SOEs may be subjected to potential managerial rent-seeking behaviors, which disproportionately increase SOE bribe propensity relative to privately owned enterprises. Specifically, our findings highlight the importance of fostering democracy and rule of law, reducing prevalence of corruption and shortening power distance in reducing the incidence of SOE bribery
Technological Pathways to Produce Compressed and Highly Pure Hydrogen from Solar Power
Hydrogen H2 produced from renewables will have a growing impact on the global energy dynamics towards sustainable and carbon neutral standards. The share of green H2 is still too low to meet the net zero target, while the demand for high quality hydrogen continues to rise. These factors amplify the need for economically viable H2 generation technologies. The present article aims at evaluating the existing technologies for high quality H2 production based on solar energy. Technologies such as water electrolysis, photoelectrochemical and solar thermochemical water splitting, liquid metal reactors and plasma conversion utilize solar power directly or indirectly as carbon neutral electrons and are reviewed from the perspective of their current development level, technical limitations and future potentia
Corruption and its effects on FDI:Analysing the interaction between the corruption levels of the home and host countries and its effects at the decision-making level
This study furthers our understanding of how corruption affects the decision-making process of allocating foreign direct investment. Drawing on the responses of 28 managers in charge of establishing operations in a highly corrupt host country, we argue that those firms based in home countries with low levels of corruption are more proactive in preparing to face corruption abroad than those based in countries with high corruption levels. This means that firms from less corrupt home countries have strategies in place to deal with high corruption abroad. This finding is based on the fact that these firms have stronger pressures to not engage in corruption from their home stakeholders. Also, these firms might not have the experience of dealing with corruption at home, which hinders their potential to deal with corruption abroad. On the other hand, those firms based in highly corrupt home countries do not have clear strategies to deal with corruption abroad. This assertion is based on the fact that these firms might have familiarity in dealing with corruption and thus, might not see it as an obstacle to operating abroad
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