Magnon breakdown in a two dimensional triangular lattice Heisenberg antiferromagnet of multiferroic LuMnO3.
The breakdown of magnons, the quasiparticles of magnetic systems, has rarely been seen. By using an inelastic neutron scattering technique, we report the observation of spontaneous magnon decay in multiferroic LuMnO3, a simple two dimensional Heisenberg triangular lattice antiferromagnet, with large spin S=2. The origin of this rare phenomenon lies in the nonvanishing cubic interaction between magnons in the spin Hamiltonian arising from the noncollinear 120° spin structure. We observed all three key features of the nonlinear effects as theoretically predicted: a rotonlike minimum, a flat mode, and a linewidth broadening, in our inelastic neutron scattering measurements of single crystal LuMnO3. Our results show that quasiparticles in a system hitherto thought of as "classical" can indeed break down.
Center for Correlated Electron Systems, Institute for Basic Science (IBS), Seoul 151-747, Korea and Department of Physics and Astronomy, Seoul National University, Seoul 151-747, Korea.
Joosung
J
Oh
Center for Correlated Electron Systems, Institute for Basic Science (IBS), Seoul 151-747, Korea and Department of Physics and Astronomy, Seoul National University, Seoul 151-747, Korea.
Manh Duc
MD
Le
Center for Correlated Electron Systems, Institute for Basic Science (IBS), Seoul 151-747, Korea and Department of Physics and Astronomy, Seoul National University, Seoul 151-747, Korea.
Jaehong
J
Jeong
Center for Strongly Correlated Materials Research, Seoul National University, Seoul 151-747, Korea and Department of Physics, Sungkyunkwan University, Suwon 440-746, Korea.
Jung-hyun
JH
Lee
ISIS Facility, STFC Rutherford Appleton Laboratory, Oxfordshire OX11 0QX, United Kingdom and Department of Physics, Brookhaven National Laboratory, Upton, New York 11973, USA.
Hyungje
H
Woo
Center for Strongly Correlated Materials Research, Seoul National University, Seoul 151-747, Korea and Department of Physics, Sungkyunkwan University, Suwon 440-746, Korea.
Wan-Young
WY
Song
ISIS Facility, STFC Rutherford Appleton Laboratory, Oxfordshire OX11 0QX, United Kingdom.
T G
TG
Perring
Chalk River Laboratories, National Research Council, Chalk River, Ontario K0J 1J0, Canada.
W J L
WJ
Buyers
Department of Physics and Astronomy and Rutgers Center for Emergent Materials, Rutgers University, Piscataway, New Jersey 08854, USA.
S-W
SW
Cheong
Center for Correlated Electron Systems, Institute for Basic Science (IBS), Seoul 151-747, Korea and Department of Physics and Astronomy, Seoul National University, Seoul 151-747, Korea and Center for Strongly Correlated Materials Research, Seoul National University, Seoul 151-747, Korea.
Je-Geun
JG
Park