title: Singlet ground state of the quantum antiferromagnet Ba(3)CuSb(2)O(9).
abstract: We present local probe results on the honeycomb lattice antiferromagnet Ba(3)CuSb(2)O(9). Muon spin relaxation measurements in a zero field down to 20 mK show unequivocally that there is a total absence of spin freezing in the ground state. Sb NMR measurements allow us to track the intrinsic susceptibility of the lattice, which shows a maximum at around 55 K and drops to zero in the low-temperature limit. The spin-lattice relaxation rate shows two characteristic energy scales, including a field-dependent crossover to exponential low-temperature behavior, implying gapped magnetic excitations.
authors.affiliation: Laboratoire de Physique des Solides, Université Paris-Sud 11, UMR CNRS 8502, 91405 Orsay, France.
authors.forename: J A
authors.initials: JA
authors.lastname: Quilliam
authors.forename: F
authors.initials: F
authors.lastname: Bert
authors.forename: E
authors.initials: E
authors.lastname: Kermarrec
authors.forename: C
authors.initials: C
authors.lastname: Payen
authors.forename: C
authors.initials: C
authors.lastname: Guillot-Deudon
authors.forename: P
authors.initials: P
authors.lastname: Bonville
authors.forename: C
authors.initials: C
authors.lastname: Baines
authors.forename: H
authors.initials: H
authors.lastname: Luetkens
authors.forename: P
authors.initials: P
authors.lastname: Mendels