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Effects of disorder and magnetic fields on certain strongly correlated systems.

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Broken translation invariance due to presence of spatially fluctuating potentials can lead to interesting effects in the ground state of typical strongly correlated systems. In this talk I will focus on a canonical example of strongly correlated system, manganites and show that depending on the way the in which the translation invariance is broken, the effect on the spin-charge-orbital ordered states, found in these materials, are drastically different. Using a real space Monte-Carlo technique, I will demonstrate that while homogeneously distributed weak scatterers break down the ordered state into a nano-scale glassy state, the presence of strong but dilute scatterers leads to a macroscopic coexistent phases in the ground state. I will discuss the general principle that causes this tendency and show how this principle can be exploited to predict new highly polarizable phase separated states across a range of electron dopings. Next, I will discuss a contrasting situation, where the ground state of the system is inherently phase separated in the presence of a magnetic field without any disorder. Here we will study the fate on the coexistent state as the field is hiked up, with and without disorder being present in the system. In the process, some striking experimental data on magnetic field melting of the charge ordered state in manganites will be explained. I will end by discussing the effects of disorder on the kinetics of this melting process, in particular, the possibility of tuning volumes of coexistent phases by following different trajectories in the relevant parameter space.

Ref: Phys. Rev. Lett. vol 99, 147206 (2007);arXiv:0710.2278;arXiv:0801.2054

This talk is part of the TCM Informal Seminar Series series.

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