Dimensional Reduction and Odd-Frequency Pairing of the Checkerboard-Lattice Hubbard Model at 1/4-Filling

TL;DR

This paper investigates how geometrical frustration in the checkerboard-lattice Hubbard model at quarter filling causes dimensional reduction, leading to unique magnetic orders and odd-frequency superconducting states near magnetic boundaries.

Contribution

It reveals the robustness of 1D behavior under certain conditions and links this to the emergence of odd-frequency pairing in the model.

Findings

Dimensional reduction occurs when t1 < t2.

Unique magnetic orders with 1D character are observed.

Odd-frequency superconducting states emerge near magnetic boundaries.

Abstract

The ferromagnetism of the checkerboard lattice Hubbard model at quarter filling is one of the few exact ferromagnetic ground states known in the family of Hubbard models. When the nearest neighbor hopping, t1, is negligible compared with the second neighbor one, t2, the system reduces to a collection of Hubbard chains. We find that the 1D character is surprisingly robust as long as t1 < t2. This phenomenon of dimensional reduction due to the geometrical frustration leads to peculiar magnetic orders with 1D character for intermediate U and is responsible for odd-frequency superconducting states close to the magnetic boundary.