We present an efficient second-order finite difference scheme for solving the
2D sine-Gordon equation, which can inherit the discrete energy conservation for
the undamped model theoretically. Due to the semi-implicit treatment for the
nonlinear term, it leads to a sequence of nonlinear coupled equations. We use a
linear iteration algorithm, which can solve them efficiently, and the
contraction mapping property is also proven. Based on truncation errors of the
numerical scheme, the convergence analysis in the discrete l2-norm is
investigated in detail. Moreover, we carry out various numerical simulations,
such as verifications of the second order accuracy, tests of energy
conservation and circular ring solitons, to demonstrate the efficiency and the
robustness of the proposed scheme.Comment: 18 pages, 7 figure