Resonant magnetic mode in superconducting 2-leg ladders

TL;DR

This paper investigates the spin dynamics in doped 2-leg ladders, revealing a magnetic excitation below the continuum that resembles the resonant mode observed in high-Tc cuprates, supported by numerical and theoretical analysis.

Contribution

It demonstrates the evolution of a hole pair-magnon bound state into a sharp magnetic mode at finite doping using numerical and field theory methods.

Findings

Identification of a sharp magnetic excitation below the two-particle continuum.

Support for a SO(6)-symmetric ladder model explaining the mode.

Discussion of similarities with high-Tc cuprate resonant modes.

Abstract

The spin dynamics of a doped 2-leg spin ladder is investigated by numerical techniques. We show that a hole pair-magnon boundstate evolves at finite hole doping into a sharp magnetic excitation below the two-particle continuum. This is supported by a field theory argument based on a SO(6)-symmetric ladder. Similarities and differences with the resonant mode of the high-T$_c$ cuprates are discussed.