High Temperature Expansion for the SU(n) Heisenberg Model in One Dimension

Thermodynamic properties of the SU(n) Heisenberg model with the nearest-neighbor interaction in one dimension are studied by means of high-temperature expansion for arbitrary n. The specific heat up to O[(βJ)²³] and the correlation function up to O[(βJ) ¹⁹] are derived with βJ being the antiferromagnetic exchange in units of temperature. The series coefficients are obtained as explicit functions of n. It is found for n > 2 that the specific heat exhibits a shoulder on the high-temperature side of a peak, The origin of this structure is clarified by deriving the temperature dependence of the correlation function. With decreasing temperature, the short-range correlation with two-site periodicity develops first, and then another correlation occurs with n-site periodicity at lower temperature, This behavior is in contrast to that of the 1/r²-model, where the specific heat shows a single peak according to the exact solution.