Magnetic superstructure in the two-dimensional quantum antiferromagnet SrCu2(BO3)2.
We report the observation of magnetic superstructure in a magnetization plateau state of SrCu2(BO3)2, a frustrated quasi-two-dimensional quantum spin system. The Cu and B nuclear magnetic resonance (NMR) spectra at 35 millikelvin indicate an apparently discontinuous phase transition from uniform magnetization to a modulated superstructure near 27 tesla, above which a magnetization plateau at 1/8 of the full saturation has been observed. Comparison of the Cu NMR spectrum and the theoretical analysis of a Heisenberg spin model demonstrates the crystallization of itinerant triplets in the plateau phase within a large rhomboid unit cell (16 spins per layer) showing oscillations of the spin polarization. Thus, we are now in possession of an interesting model system to study a localization transition of strongly interacting quantum particles.
Kodama
K
K
Institute for Solid State Physics, University of Tokyo, Kashiwa, Chiba 277-8581, Japan.
Takigawa
M
M
Horvatić
M
M
Berthier
C
C
Kageyama
H
H
Ueda
Y
Y
Miyahara
S
S
Becca
F
F
Mila
F
F