Hamburg 2001 – scientific programme
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TT: Tiefe Temperaturen
TT 20: Niederdimesnionale Systeme, Magnetotransport, Quantenhalleffekt II
TT 20.8: Talk
Thursday, March 29, 2001, 11:15–11:30, A
Thermal conductivity of the two-dimensional spin system SrCu2(BO3)2 — •M. Hofmann1, T. Lorenz1, H. Kierspel1, O. Zabara1, A. Freimuth1, G. Uhrig2, and H. Kageyama3 — 1II. Physikalisches Institut, Universität zu Köln, 50937 Köln, Germany — 2Institut für Theoretische Physik, Universität zu Köln, 50937 Köln, Germany — 3Institut for Solid State Physics, University of Tokyo, Tokyo 106-8666, Japan
The two-dimensional spin-gap system SrCu2(BO3)2 is an
experimental realisation of the frustrated Shastry-Sutherland model
on a square lattice.
We present measurements of the thermal conductivity parallel
(κa) and perpendicular (κc) to the layers
in magnetic fields up to 17 T. As a function of temperature,
both κa and κc show a double peak structure
with two maxima at ∼ 4 K and ∼ 60 K for κa
and at ∼ 4 K and ∼ 30 K for κc. In a magnetic field
the low temperature maxima are strongly suppressed
for both κa and κc.
In view of the magnetic anisotropy
of the system and of the local character of the spin triplet excitations,
we
suggest that the heat current is due to phonons.
The field- and temperature-dependences of κ can be well
described in terms of resonant scattering of phonons on
singlet and triplet excitations.