Doping-dependent magnetization plateaux in p-merized Hubbard chains

TL;DR

This paper investigates how periodic modulation of hopping in Hubbard chains influences magnetization plateaux, revealing both gapped and gapless plateau states depending on filling and periodicity.

Contribution

It demonstrates the emergence of magnetization plateaux at various values depending on periodicity and filling, including irrational values, and analyzes the gapless modes on certain plateaux.

Findings

Plateaux occur at specific magnetizations depending on periodicity p and filling n.

Charge gaps open at commensurate fillings, leading to fully gapped plateaux.

Gapless modes can exist on certain plateaux, affecting thermodynamic properties.

Abstract

We study zero-temperature Hubbard chains with periodically modulated hopping at arbitrary filling n and magnetization m. We show that the magnetization curves have plateaux at certain values of m which depend on the periodicity p and the filling. At commensurate filling n a charge gap opens and then magnetization plateaux correspond to fully gapped situations. However, plateaux also arise in the magnetization curves at fixed n between the commensurate values and then the plateau-value of of m depends continuously on n and can thus also become irrational. In particular for the case of dimerized hopping (p=2) and fixed doping we find that a plateau appears at m=1-n. In this case, there is still a gapless mode on the plateau leading to thermodynamic behavior which is different from a completely gapped situation.