Enhanced low-temperature entropy and flat-band ferromagnetism in the t-J model on the sawtooth lattice

Abstract

Using the example of the sawtooth chain, we argue that the t-J model shares important features with the Hubbard model on highly frustrated lattices. The lowest single-fermion band is completely flat (for a specific choice of the hopping parameters $t_{i,j}$ in the case of the sawtooth chain), giving rise to single-particle excitations which can be localized in real space. These localized excitations do not interact for sufficient spatial separations such that exact many-electron states can also be constructed. Furthermore, all these excitations acquire zero energy for a suitable choice of the chemical potential $\mu$. This leads to: (i) a jump in the particle density at zero temperature, (ii) a finite zero-temperature entropy, (iii) a ferromagnetic ground state with a charge gap when the flat band is fully occupied and (iv) unusually large temperature variations when $\mu$ is varied adiabatically at finite temperature.

arXiv comment2 pages including 2 figures, uses elsart style files; (proceedings of ICM 2006)

References in corpus (11)

• From Nagaoka's ferromagnetism to flat-band ferromagnetism and beyond: An introduction to ferromagnetism in the Hubbard model
• Macroscopic magnetization jumps due to independent magnons in frustrated quantum spin lattices
• Enhanced magnetocaloric effect in frustrated magnets
• Exact low-temperature behavior of kagome antiferromagnet at high fields
• Magnetocaloric effect in one-dimensional antiferromagnets
• Exact eigenstates and macroscopic magnetization jumps in strongly frustrated spin lattices
• Quantum magnetism in two dimensions: From semi-classical Néel order to magnetic disorder
• Universal low-temperature behavior of frustrated quantum antiferromagnets in the vicinity of the saturation field
• Finite low-temperature entropy of some strongly frustrated quantum spin lattices in the vicinity of the saturation field
• High field properties of geometrically frustrated magnets
• Entropy of fermionic models on highly frustrated lattices

Cited by in corpus (5)

• Low-temperature properties of the Hubbard model on highly frustrated one-dimensional lattices
• The sawtooth chain: From Heisenberg spins to Hubbard electrons
• Bilayer Linearized Tensor Renormalization Group Approach for Thermal Tensor Networks
• Ground-state degeneracy and low-temperature thermodynamics of correlated electrons on highly frustrated lattices
• Low-temperature thermodynamics of one class of flat-band models