Quantum-critical spin dynamics in a Tomonaga-Luttinger liquid studied with muon-spin relaxation

J. S. Möller, University of Oxford
T. Lancaster, Durham University
S. J. Blundell, University of Oxford
F. L. Pratt, ISIS Neutron and Muon Source
P. J. Baker, ISIS Neutron and Muon Source
F. Xiao, Durham University
R. C. Williams, Durham University
W. Hayes, University of Oxford
M. M. Turnbull, Clark University
C. P. Landee, Clark University

Abstract

We demonstrate that quantum-critical spin dynamics can be probed in high magnetic fields using muon-spin relaxation (μ+SR). Our model system is the strong-leg spin ladder bis(2,3-dimethylpyridinium) tetrabromocuprate (DIMPY). In the gapless Tomonaga-Luttinger liquid phase we observe finite-temperature scaling of the μ+SR 1/T1 relaxation rate which allows us to determine the Luttinger parameter K. We discuss the benefits and limitations of local probes compared with inelastic neutron scattering.