Volume 81, Number 6, March 2008
Article Number 67004
Number of page(s) 5
Section Condensed Matter: Electronic Structure, Electrical, Magnetic and Optical Properties
Published online 29 February 2008
EPL, 81 (2008) 67004
DOI: 10.1209/0295-5075/81/67004

Field dependence of the quantum ground state in the Shastry-Sutherland system SrCu2(BO3)2

F. Levy1, I. Sheikin1, C. Berthier1, M. Horvatic1, M. Takigawa2, H. Kageyama3, T. Waki2 and Y. Ueda2

1  Grenoble High Magnetic Field Laboratory (GHMFL), CNRS - BP 166, 38042 Grenoble Cedex 09, France
2  Institute for Solid State Physics, University of Tokyo - Kashiwanoha, Kashiwa, 277-8581, Japan
3  Department of Chemistry, Graduate School of Science, Kyoto University - Kyoto 606-8502, Japan

received 30 November 2007; accepted in final form 30 January 2008; published March 2008
published online 29 February 2008

We present magnetic torque measurements on the Shastry-Sutherland quantum spin system SrCu2(BO3)2 in fields up to 31 T and temperatures down to 50 mK. A new quantum phase is observed in a 1 T field range above the 1/8 plateau, in agreement with recent NMR results. Since the presence of the DM coupling precludes the existence of a true Bose-Einstein condensation and the formation of a supersolid phase in SrCu2 (BO3)2, the exact nature of the new phase in the vicinity of the plateau remains to be explained. Comparison between magnetization and torque data reveals a huge contribution of the Dzyaloshinskii-Moriya interaction to the torque response. Finally, our measurements demonstrate the existence of a supercooling due to adiabatic magnetocaloric effects in pulsed field experiments.

75.10.Jm - Quantized spin models.
75.30.Kz - Magnetic phase boundaries (including magnetic transitions, metamagnetism, etc.).
75.30.Sg - Magnetocaloric effect, magnetic cooling.

© EPLA 2008