### Session X18: Focus Session: Low D/Frustrated Magnetism - Spin Chains & Ladders

2:30 PM–5:30 PM, Thursday, March 24, 2011
Room: D172

Chair: Marcelo Jamie, Los Alamos National Laboratory

Abstract ID: BAPS.2011.MAR.X18.10

### Abstract: X18.00010 : Field-Induced Gap in a Quantum Spin-1/2 Chain in a Strong Magnetic Field

4:42 PM–4:54 PM

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#### Authors:

S. Zvyagin
(Dresden High Magnetic Field Laboratory (HLD/FZD), Dresden, Germany)

M. Ozerov
(Dresden High Magnetic Field Laboratory (HLD/FZD), Dresden, Germany)

J. Wosnitza
(Dresden High Magnetic Field Laboratory (HLD/FZD), Dresden, Germany)

E. \v{C}i\v{z}m\'{a}r
(CLTP/P.J.~Safarik University, Ko\v{s}ice, Slovakia)

R. Feyerherm
(HZB, Berlin, Germany)

S.R. Manmana
(JILA, Dept. of Physics, University of Colorado, Boulder, USA)

F. Mila
(Inst. for Theor. Physics, EPF Lausanne, Lausanne, Switzerland)

Magnetic excitations in copper pyrimidine dinitrate, a spin-1/2 antiferromagnetic chain with alternating $g$-tensor and Dzyaloshinskii-Moriya interactions that exhibits a field-induced spin gap, are probed by means of pulsed-field electron spin resonance spectroscopy. In particular, we report on a minimum of the gap in the vicinity of the saturation field $H_{sat}=48.5$ T associated with a transition from the sine-Gordon region (with soliton-breather elementary excitations) to a spin-polarized state (with magnon excitations). This interpretation is fully confirmed by the quantitative agreement over the entire field range of the experimental data with the DMRG investigation of the spin-1/2 Heisenberg chain with a staggered transverse field.

To cite this abstract, use the following reference: http://meetings.aps.org/link/BAPS.2011.MAR.X18.10