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Phase diagram of the half-filled ionic Hubbard model in the limit of strong correlations

Chattopadhyay, Anwesha and Bag, Soumen and Krishnamurthy, HR and Garg, Arti (2019) Phase diagram of the half-filled ionic Hubbard model in the limit of strong correlations. In: PHYSICAL REVIEW B, 99 (15).

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Official URL: https://doi.org/10.1103/PhysRevB.99.155127


We investigate the ionic Hubbard model (IHM) at half-filling in the limit of strong correlations and large ionic potential. The low-energy effective Hamiltonian in this limit, obtained by a similarity transformation, is a modified t-J model with effective second-neighbor hopping terms. We explore the possibilities of d-wave pairing and extended s-wave pairing superconducting (SC) phases on a two-dimensional square lattice at zero temperature within a Gutzwiller projected renormalized mean-field theory. In the sector of solutions that forbid spin-ordering, the system shows a finite nonzero d-wave as well as extended s-wave pairing amplitude for Delta similar to U >> t. The width of the superconducting phase in U - Delta regime shrinks with increase in U and Delta, though the extended s-wave pairing phase is higher in energy than the d-wave pairing superconducting phase. But in a spin-resolved renormalized mean-field calculation, which allows for an antiferromagnetic (AF) order along with the d-wave or extended s-wave pairing, the SC phase is no longer viable and the system shows a direct transition from an AF ordered phase to a paramagnetic band insulator. Except for a thin sliver of a half-metallic AF phase close to the AF transition point, most of the AF ordered phase is a Mott insulator. We benchmarked the AF Mott insulator to band insulator transition within the Gutzwiller projected renormalized mean-field theory against the dynamical mean-field theory solved using continuous time quantum Monte Carlo. Our work suggests that the ground-state phase diagram of the IHM at half-filling in the limit of extreme correlations does not have any SC phase. The SC phase seen in the paramagnetic sector is a metastable phase, being higher in energy than the AF Mott insulator phase.

Item Type: Journal Article
Additional Information: Copyright of this article belongs to AMER PHYSICAL SOC
Department/Centre: Division of Physical & Mathematical Sciences > Physics
Date Deposited: 28 May 2019 06:12
Last Modified: 28 May 2019 06:12
URI: http://eprints.iisc.ac.in/id/eprint/62593

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