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Phase diagram of the (bosonic) Double-Exchange Model

J. L. Alonso·A. Cruz·L. A. Fernandez·S. Jimenez·V. Martin-Mayor·J. J. Ruiz-Lorenzo·A. Tarancon
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Abstract

The phase diagram of the simplest approximation to Double-Exchange systems, the bosonic Double-Exchange model with antiferromagnetic super-exchange coupling, is fully worked out by means of Monte Carlo simulations, large-N expansions and Variational Mean-Field calculations. We find a rich phase diagram, with no first-order phase transitions. The most surprising finding is the existence of a segment like ordered phase at low temperature for intermediate AFM coupling which cannot be detected in neutron-scattering experiments. This is signaled by a maximum (a cusp) in the specific heat. Below the phase-transition, only short-range ordering would be found in neutron-scattering. Researchers looking for a Quantum Critical Point in manganites should be wary of this possibility. Finite-Size Scaling estimates of critical exponents are presented, although large scaling corrections are present in the reachable lattice sizes.

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J. L. Alonso, A. Cruz, L. A. Fernandez, S. Jimenez, V. Martin-Mayor, J. J. Ruiz-Lorenzo, A. Tarancon. 2004-02-27. Phase diagram of the (bosonic) Double-Exchange Model. https://doi.org/10.1103/physrevb.71.014420

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