# Superconductivity in repulsively interacting fermions on a diamond chain: Flat-band-induced pairing

@article{Kobayashi2016SuperconductivityIR,
title={Superconductivity in repulsively interacting fermions on a diamond chain: Flat-band-induced pairing},
author={Keita Kobayashi and Masahiko Okumura and Susumu Yamada and Masahiko Machida and Hideo Aoki},
journal={Physical Review B},
year={2016},
volume={94},
pages={214501}
}
To explore whether a flat-band system can accommodate superconductivity, we consider repulsively interacting fermions on the diamond chain, a simplest quasi-one-dimensional system that contains a flat band. Exact diagonalization and the density-matrix renormalization group (DMRG) are used to show that we have a significant binding energy of a Cooper pair with a long-tailed pair-pair correlation in real space when the total band filling is slightly below $1/3$, where the dispersive band…
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## References

SHOWING 1-10 OF 40 REFERENCES
Phase-separated ferromagnetism in a spin-imbalanced system of Fermi atoms loaded in an optical ladder: A density-matrix renormalization-group study
• Physics
• 2011
We consider repulsively interacting, cold fermionic atoms loaded on an optical ladder lattice in a trapping potential. The density-matrix renormalization-group method is used to numerically calculate
Pairing correlation in the three-leg Hubbard ladder : Renormalization group and quantum Monte Carlo studies
• Physics
• 1998
In order to investigate the validity of a conjecture that correlated electrons in ladders having even-numbered legs exhibit superconductivity accompanied by a spin gap while odd ones do not, the
Phase diagram and pair Tomonaga-Luttinger liquid in a Bose-Hubbard model with flat bands
• Physics
• 2013
To explore superfluidity in flat-band systems, we consider a Bose-Hubbard model on a cross-linked ladder with $\pi$ flux, which has a flat band with a gap between the other band for noninteracting
Coherent driving and freezing of bosonic matter wave in an optical Lieb lattice
• Physics, Medicine
• 2015
This work reports the realization of a “Lieb lattice” configuration with an optical lattice, which has a flat energy band as the first excited state, and investigates the inter-sublattice dynamics of the system by projecting the sublattices population onto the band population.
Topological states in a ladder-like optical lattice containing ultracold atoms in higher orbital bands.
• Physics, Medicine
Nature communications
• 2013
A topological phase of interacting fermionic atoms on a two-leg ladder derived from the above experimental optical lattice by dimension reduction is unveiled, requiring neither spin-orbit coupling nor other known mechanisms like p-wave pairing, artificial gauge field or rotation.
Restoring phase coherence in a one-dimensional superconductor using power-law electron hopping
• Physics
• 2013
In a one-dimensional (1D) superconductor, zero-temperature quantum fluctuations destroy phase coherence. Here we put forward a mechanism which can restore phase coherence: power-law hopping. We study
High T_c superconductivity due to coexisting wide and narrow bands: A fluctuation exchange study on the Hubbard ladder as a test case
• Physics
• 2005
We propose that when the Fermi level lies within a wide band and also lies close to but not within a coexisting narrow band, high $T_c$ superconductivity may take place due to the large number of
Doped A B 2 Hubbard chain: Spiral, Nagaoka and resonating-valence-bond states, phase separation, and Luttinger-liquid behavior
• Physics
• 2006
We present an extensive numerical study of the Hubbard model on the doped AB$_2$ chain, both in the weak coupling and the infinite-U limit. Due to the special unit cell topology, this system displays
Correlation functions in the three-chain Hubbard ladder.
• Kimura, Aoki
• Physics, Medicine
Physical review. B, Condensed matter
• 1996
In order to check whether odd-numbered Tomonaga-Luttinger ladders are dominated by antiferromagnetic correlations associated with gapless spin excitations, correlation functions of the doped
Geometry induced pair condensation
• Physics
• 2013
We study a one-dimensional model of interacting bosons on a lattice with two flat bands. Regular condensation is suppressed due to the absence of a well defined minimum in the single particle