Doped two-leg ladder with ring exchange

TL;DR

This paper investigates how ring exchange interactions influence the magnetic excitations and superconducting pairing in doped two-leg ladders, revealing effects on resonant modes and spin gaps through advanced computational methods.

Contribution

It provides new insights into the impact of ring exchange on magnetic excitations and phase stability in doped two-leg ladder systems, combining ED and DMRG techniques.

Findings

Ring exchange stabilizes a resonant mode from hole pair-magnon bound states.

Doping reopens a spin gap near the zero-doping critical point.

The cyclic term affects the nature and weights of low energy magnetic excitations.

Abstract

The effect of a ring exchange on doped two-leg ladders is investigated combining exact diagonalization (ED) and density matrix renormalization group (DMRG) computations. We focus on the nature and weights of the low energy magnetic excitations and on superconducting pairing. The stability with respect to this cyclic term of a remarkable resonant mode originating from a hole pair-magnon bound state is examined. We also find that, near the zero-doping critical point separating rung-singlet and dimerized phases, doping reopens a spin gap.