Study of the XY chain with long-range interactions
具有长程相互作用S-1/2 XY链的研究

Using the mean-field Jordan-Wigner transformation analysis, we have studied the one-dimensional spin-1/2 XY chain with Z-directional uniform long-range interactions in the external magnetic field. We have obtained such results as the Helmholtz free energy, internal energy, specific heat, magnetization and isothermal susceptibility. We also discuss the first and second-order phase transitions of the system at a finite temperature. Our results agree with results published in literature.