Spin and charge modulations in a single hole doped Hubbard ladder -- verification with optical lattice experiments

TL;DR

This paper demonstrates how a single hole in a 2-leg Hubbard ladder causes spin and charge density modulations, revealing underlying quantum interference effects that can be experimentally observed with cold atom systems.

Contribution

It provides a detailed analysis of how phase strings influence spin and charge modulations in a Hubbard ladder, connecting theoretical predictions with potential cold atom experiments.

Findings

Single hole induces pronounced spin and charge modulations.

Modulations linked to interference of phase strings and are observable in short ladders.

Properties persist in small systems and can be tested with cold atom experiments.

Abstract

We show that pronounced modulations in spin and charge densities can be induced by the insertion of a single hole in an otherwise half-filled 2-leg Hubbard ladder. Accompanied with these modulations is a loosely bound structure of the doped charge with a spin-1/2, in contrast to the tightly bound case where such modulations are absent. These behaviors are caused by the interference of the Berry phases associated a string of flipped spins (or "phase strings") left behind as a hole travels through a spin bath with a short-range anti-ferromagnetic order. The key role of the phase strings is also reflected in how the system respond to increasing spin polarization, increasing the on-site repulsion, addition of a second hole, and increasing asymmetry between intra- and inter-chain hopping. Remarkably, all these properties persist down to ladders as short as $\sim 10$ sites. They can therefore be studied in cold atom experiments using the recently developed fermion microscope.