Effect of strain on the transport properties of the manganite systems

The effect of strain on the resistivity and thermopower of ferromagnetic manganites has been examined based on the model that incorporates the electron-lattice interaction through the Jahn-Teller effect and an effective hopping determined by nearest neighbour spin-spin correlation of t2g electrons. The metal insulator transition temperature associated with resistivity decreases with increase in strain. In the presence of large strain the system remains in the semiconducting state. Thermopower (S) is positive and increasing function of strain and it exhibits a maximum with temperature. The temperature where maximum of S appears, shifts towards higher (lower) value with in the presence of magnetic field (strain). A large magneto-thermopower that depends on strain is obtained around metal-insulator transition.Comment: 11pages, 4 figure

Can market failure cause political failure?

We study how inefficiencies of market failure may be further amplified by political choices made by interest groups created in the inefficient market. We take an occupational choice framework, where agents are endowed heterogeneously with wealth and talent. In our model, market failure due to unobservability of talent endogenously creates a class structure that affects voting on institutional reform. In contrast to the world without market failure where the electorate unanimously vote in favour of surplus maximising institutional reform, we find that the preferences of these classes are often aligned in ways that creates a tension between surplus maximising and politically feasible institutional reforms

Pseudogap and its influence on normal and superconducting states of cuprates

A model incorporating simultaneous superconducting and lattice instabilities has been studied in detail to estimate the nature of coupling and inter-play between them. The phase diagram is obtained in the temperature-filling plane at different values of the parameters of the model. It is found that a pseudogap develops in the distorted phase that inhibits the appearance of the superconducting transition. The superconducting instability is strongest for the regime of filling where the van Hove singularity in the 2D density of states is close to the chemical potential. The pseudogap, developed in the distorted phase, is a function of temperature via the temperature dependence of the distortion itself. Transport properties, namely resistivity and thermopower are found to be strongly dependent on the variations of the pseudogap.Comment: 14 pages, 11 figure