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SUMMARY:The effect of staggered local environments on quantum spin chains 
 - Paul Goddard - University of Warwick
DTSTART:20250709T101500Z
DTEND:20250709T110000Z
UID:TALK228199@talks.cam.ac.uk
CONTACT:Mads Fonager Hansen
DESCRIPTION:I will discuss the properties of non-linear antiferromagnetic 
 (AFM) chains\, in which the orientation of the local environment of the ma
 gnetic ion is 'staggered'\, i.e. alternates in direction from site to site
 . Spin-1/2 non-linear chains exhibit additional terms in their Hamiltonian
 s compared to linear chains\, including non-trivial staggered g-tensors an
 d Dzyalonshinskii-Moriya interactions. On application of an external magne
 tic field\, these energy scales can give rise to staggered fields\, field-
 dependent energy gaps and low-temperature excitation spectra containing bo
 th breather and soliton modes\, observations that have previously been exp
 lained via the sine-Gordon model of quantum-field theory. Spin-1 AFM chain
 s are known to adopt ground states that differ fundamentally from their sp
 in-1/2 counterparts\, an example being the topological Haldane-gapped phas
 e\, but until recently the effect of staggered local environments on spin-
 1 systems had not been explored. \n\nHere\, I present magnetometry\, muon-
 spin rotation and neutron-scattering data on several new examples of non-l
 inear spin chains. I will show that a chiral spin-1/2 chain with a four-fo
 ld periodic rotation of the local spin environment leads to properties dis
 tinct from the alternating chains previously studied. I will also discuss 
 the results obtained by measuring non-linear spin-1 AFM chains\, why these
  differ from the spin-1/2 materials and how competition between single-ion
  anisotropy and magnetic exchange can give rise to non-collinear or chiral
  magnetic ground-state structures. \n\nJ. Liu et. al. Phys. Rev. Lett. 122
 \, 057207 (2019)\n\nS. Vaidya et. al.\, Phys. Rev. B 110\, 174438 (2024)\n
 \nS. Vaidya et. al.\, PRB 111\, 014421 (2025)
LOCATION:Seminar Room 1\, RDC
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