Low-temperature specific heat study of SrCu2(BO3)(2) with an exactly solvable ground state

The specific heat of a two-dimensional spin gap system SrCu2(BO3)(2) realiz ing the Shastry-Sutherland model was measured between 1.3 and 25 K under va rious magnetic fields up to 12 T. The analysis based on an isolated dimer m odel in a low temperature region revealed that the value of the spin gap at zero field is Delta = 34.4 K. It turned out that Delta decreases in propor tion to H due to the Zeeman splitting of the excited triplet levels. This s implest model, however, fails to reproduce the result in a high-temperature region, suggesting rather strong spin-spin correlation of the system. (C) 2000 MAIK "Nauka/Interperiodica".