The t-Jz ladder

TL;DR

This paper investigates the phase diagram of the two-leg t-Jz ladder using density matrix renormalization group methods, revealing phases like Luther-Emery and Tomonaga-Luttinger, and examining energy gaps and correlation functions.

Contribution

It provides the first detailed numerical analysis of the t-Jz ladder's phase diagram, including energy gaps, correlation functions, and the behavior of the one-hole gap in the Nagaoka limit.

Findings

Vanishing effective Lagrangian velocity at half-filling

Disagreement of one-hole gap with theoretical predictions in Nagaoka limit

Identification of Luther-Emery and Tomonaga-Luttinger phases near half- and quarter-filling

Abstract

The phase diagram of the two-leg t-Jz ladder is explored, using the density matrix renormalization group method. Results are obtained for energy gaps, electron density profiles and correlation functions for the half-filled and quarter-filled cases. The effective Lagrangian velocity parameter is shown to vanish at half-filling. The behaviour of the one-hole gap in the Nagaoka limit is investigated, and found to disagree with theoretical predictions. A tentative phase diagram is presented, which is quite similar to the full t-J ladder, but scaled up by a factor of about two in coupling. Near half-filling a Luther-Emery phase is found, which may be expected to show superconducting correlations, while near quarter-filling the system appears to be in a Tomonaga-Luttinger phase.