title: Quantum-critical spin dynamics in quasi-one-dimensional antiferromagnets.
abstract: By means of nuclear spin-lattice relaxation rate T(1)(-1), we follow the spin dynamics as a function of the applied magnetic field in two gapped quasi-one-dimensional quantum antiferromagnets: the anisotropic spin-chain system NiCl(2)-4SC(NH(2))(2) and the spin-ladder system (C(5)H(12)N)(2)CuBr(4). In both systems, spin excitations are confirmed to evolve from magnons in the gapped state to spinons in the gapless Tomonaga-Luttinger-liquid state. In between, T(1)(-1) exhibits a pronounced, continuous variation, which is shown to scale in accordance with quantum criticality. We extract the critical exponent for T(1)(-1), compare it to the theory, and show that this behavior is identical in both studied systems, thus demonstrating the universality of quantum-critical behavior.
authors.affiliation: Laboratoire National des Champs Magnétiques Intenses, LNCMI-CNRS (UPR3228), UJF, UPS and INSA, BP 166, 38042 Grenoble Cedex 9, France.
authors.forename: S
authors.initials: S
authors.lastname: Mukhopadhyay
authors.forename: M
authors.initials: M
authors.lastname: Klanjšek
authors.forename: M S
authors.initials: MS
authors.lastname: Grbić
authors.forename: R
authors.initials: R
authors.lastname: Blinder
authors.forename: H
authors.initials: H
authors.lastname: Mayaffre
authors.forename: C
authors.initials: C
authors.lastname: Berthier
authors.forename: M
authors.initials: M
authors.lastname: Horvatić
authors.forename: M A
authors.initials: MA
authors.lastname: Continentino
authors.forename: A
authors.initials: A
authors.lastname: Paduan-Filho
authors.forename: B
authors.initials: B
authors.lastname: Chiari
authors.forename: O
authors.initials: O
authors.lastname: Piovesana