Entropy of fermionic models on highly frustrated lattices

Abstract

Spinless fermions on highly frustrated lattices are characterized by a lowest single-particle band which is completely flat. Concrete realizations are provided by the sawtooth chain and the kagome lattice. For these models a real-space picture is given in terms of localized states. Furthermore, we find a finite zero-temperature entropy for a suitable choice of the chemical potential. The entropy is computed numerically at finite temperature and one observes a strong cooling effect during adiabatic changes of the chemical potential. We argue that the localized states, the associated zero-temperature entropy and thus also the large temperature variations carry over to the repulsive Hubbard model. The relation to flat-band ferromagnetism is also discussed briefly.

10 pages including 5 figues; to appear in Condensed Matter Physics; proceedings of the conference "Statistical Physics 2005: Modern Problems and New Applications", Lviv, 28-30 August 2005

References in corpus (3)

• Sign change of the Grueneisen parameter and magnetocaloric effect near quantum critical points
• High field properties of geometrically frustrated magnets
• Quantum Theory of Molecular Magnetism

Cited by in corpus (12)

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• Low-temperature thermodynamics for a flat-band ferromagnet: Rigorous versus numerical results
• The sawtooth chain: From Heisenberg spins to Hubbard electrons
• Reentrant phenomenon in the exactly solvable mixed spin-1/2 and spin-1 Ising-Heisenberg model on diamond-like decorated planar lattices
• Bilayer Linearized Tensor Renormalization Group Approach for Thermal Tensor Networks
• Exact eigenstates of highly frustrated spin lattices probed in high fields
• Unusual field-induced transitions in exactly solved mixed spin-(1/2,1) Ising chain with axial and rhombic zero-field splitting parameters
• Enhanced low-temperature entropy and flat-band ferromagnetism in the t-J model on the sawtooth lattice
• Ground-state degeneracy and low-temperature thermodynamics of correlated electrons on highly frustrated lattices