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arXiv · 1709.09992

Temperature and doping induced instabilities of the repulsive Hubbard model on Lieb lattice

Pramod Kumar·Tuomas I. Vanhala·Päivi Törmä
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Abstract

The properties of a phase at finite interactions can be significantly influenced by the underlying dispersion of the non-interacting Hamiltonian. We demonstrate this by studying the repulsive Hubbard model on the $2$D Lieb lattice, which has a flat band for vanishing interaction $U$. We perform real-space dynamical mean-field theory calculations at different temperatures and dopings using a continuous time quantum Monte Carlo impurity solver. Studying the frequency dependence of the self-energy, we show that a finite temperature non-magnetic non-Fermi liquid behavior is a concomitant of the flat band singularity. At half-filling we also find a magnetically ordered region, where the order parameter varies linearly with the interaction strength, and a strongly correlated Mott insulating phase. The double occupancy decreases sharply for small $U$, highlighting the flat band contribution. Away from half-filling, we observe the stripe order, i.e. an inhomogeneous spin and charge density wave of finite wavelength which turns into a sub-lattice ordering at higher temperatures.

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Pramod Kumar, Tuomas I. Vanhala, Päivi Törmä. 2017-09-28. Temperature and doping induced instabilities of the repulsive Hubbard model on Lieb lattice. https://doi.org/10.1103/physrevb.96.245127

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