Magnetic bound states in the quarter-filled ladder system $\alpha'-NaV_{2}O_{5}$}

TL;DR

This paper investigates magnetic bound states in alpha'-NaV2O5, revealing a complex dimerized phase with multiple bound states, challenging simplified spin chain models and proposing a dynamic superposition as the ground state.

Contribution

It demonstrates the necessity of considering the full ladder topology over simplified spin chain models in the dimerized phase of alpha'-NaV2O5.

Findings

Observation of three magnetic bound states in the dimerized phase

Challenge to the effective spin chain mapping for T < T_{SP}

Proposal of a dynamic superposition of dimer configurations as the ground state

Abstract

Raman scattering in the quarter-filled spin ladder system alpha'-NaV_2O_5 shows in the dimerized singlet ground state ($T \leq T_{SP}=35K$) an unexpected sequence of three magnetic bound states. Our results suggest that the recently proposed mapping onto an effective spin chain for $T > T_{SP}$ has to be given up in favor of the full topology and exchange paths of a ladder in the dimerized phase for $T < T_{SP}$. As the new ground state we propose a dynamic superposition of energetically nearly degenerate dimer configurations on the ladder.