Faculté des sciences et de médecine

Entropy and specific heat of the infinite-dimensional three-orbital Hubbard model

Yue, Changming ; Werner, Philipp

In: Physical Review B, 2020, vol. 102, no. 8, p. 085102

The Hund's coupling in multiorbital Hubbard systems induces spin freezing and associated Hund metal behavior. Using dynamical mean-field theory, we explore the effect of local moment formation, spin, and charge excitations on the entropy and specific heat of the three-orbital model. For fillings 2≲n<3 and low temperature, we demonstrate a substantial enhancement of the entropy in the... More

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    Summary
    The Hund's coupling in multiorbital Hubbard systems induces spin freezing and associated Hund metal behavior. Using dynamical mean-field theory, we explore the effect of local moment formation, spin, and charge excitations on the entropy and specific heat of the three-orbital model. For fillings 2≲n<3 and low temperature, we demonstrate a substantial enhancement of the entropy in the spin-frozen metal phase to values comparable to the half-filled Mott insulator. We also discuss the appearance of entropy plateaus and peaks in the specific heat associated with the activation of spin and charge fluctuations at high temperature. The temperature scale for charge excitations is almost independent of filling and given by ≈0.2U, with U the intraorbital repulsion. Local spin excitations become relevant for filling n>1 and their characteristic temperature is proportional to the Hund coupling J, with a filling-dependent prefactor. The analysis of the specific heat in the atomic limit yields accurate predictions for these features in the strong-coupling regime.