Submitted on April 16, 2007
Accepted on July 12, 2007
Mesoscopic Phase Coherence in a Quantum Spin Fluid
Guangyong Xu 1,
C. Broholm 2,
Yeong-Ah Soh 3,
G. Aeppli 4,
J. F. DiTusa 5,
Yin Cheng 2,
M. Kenzelmann 2,
C. D. Frost 6,
T. Ito 7,
K. Oka 7,
H. Takagi 8
1 Department of Physics and Astronomy, The Johns Hopkins University, Baltimore, MD 21218, USA; Condensed Matter Physics and Materials Sciences Department, Brookhaven National Laboratory, Upton, NY 11973, USA.
2 Department of Physics and Astronomy, The Johns Hopkins University, Baltimore, MD 21218, USA; NIST Center for Neutron Research, National Institute of Standards and Technology, NIST, Gaithersburg, MD 20899, USA.
3 Department of Physics and Astronomy, Dartmouth College, Hanover, NH 03755, USA.
4 London Centre for Nanotechnology and Department of Physics and Astronomy, University College London, 17-19 Gordon Street, London, WC1H OAH UK.
5 Department of Physics and Astronomy, Louisiana State University, Baton Rouge, LA 70803, USA.
6 ISIS Facility, Rutherford Appleton Laboratory, Chilton, Didcot OX11 0QX, UK.
7 National Institute of Advanced Industrial Science and Technology, Tsukuba, Ibaraki 305-8562, Japan.
8 National Institute of Advanced Industrial Science and Technology, Tsukuba, Ibaraki 305-8562, Japan; Department of Advanced Materials Science, Graduate School of Frontier Sciences, University of Tokyo, Kashiwa, Chiba 277-8561, Japan.
Mesoscopic quantum phase coherence is important because it improves the prospects for handling quantum degrees of freedom in technology. Here we show that the development of such coherence can be monitored using magnetic neutron scattering from a one-dimensional spin chain Y2BaNiO5, a quantum spin fluid where no classical, static magnetic order is present. In the cleanest samples, the quantum coherence length is 20 nm, almost an order of magnitude larger than the classical antiferromagnetic correlation length of 3 nm. We also demonstrate that the coherence length can be modified by static and thermally activated defects in a quantitatively predictable manner.
