Incommensurate nodes in the energy spectrum of weakly coupled antiferromagnetic Heisenberg ladders

TL;DR

This paper studies weakly coupled antiferromagnetic Heisenberg ladders using bond-mean-field theory, revealing incommensurate nodes in the energy spectrum that influence magnetic properties and align with experimental observations.

Contribution

It introduces a theoretical analysis of incommensurate nodes in the energy spectrum of weakly coupled ladders, providing new insights into their magnetic behavior and experimental relevance.

Findings

Energy spectrum vanishes at incommensurate wavevectors

Spin susceptibility becomes linear at low temperature

Results agree with experiments on SrCu2O3 and (VO)2P2O7

Abstract

Heisenberg ladders are investigated using the bond-mean-field theory [M.Azzouz, Phys. Rev. B 48, 6136 (1993)]. The zero inter-ladder coupling energy gap, the uniform spin susceptibility and the nuclear magnetic resonance spin-relaxation rate are calculated as a function of temperature and magnetic field. For weakly coupled ladders, the energy spectrum vanishes at incommensurate wavevectors giving rise to nodes. As a consequence, the spin susceptibility becomes linear at low temperature. Our results for the single ladder successfully compare to experiments on SrCu_2O_3 and (VO)_2P_2O_7 materials and new predictions concerning the coupling to the magnetic field are made.