Towards Excitations in Correlated Systems with Density Matrix Embedding Theory

The density matrix embedding theory (DMET) provides a framework of describing the strongly correlated systems, which has shown the power of calculating global ground states and treating the excited states dominant in a single embedding space. However, DMET method has not yet achieved the excited-state calculation involving the collective interaction among various impurities. We fulfill this gap in this work by combining embedding theory with a general ansatz of local excitation operators, enabling DMET to approximate excitation bases and effective Hamiltonian. We acquire the excitation energies of one-dimensional and two-dimensional Hubbard models and reproduce various Green's function properties with cheap sub-problems of embedding space, leading to a broad prospect of treating excitation spectra of larger correlated lattices.