Geometrical pumping in spin coupled double quantum dots

We analytically investigate the non-equilibrium pumping for a double quantum dots system on the basis of the quantum master equation (QME), where the double quantum dots are connected to two external leads by the spin coupling. Each of leads has two tunable parameters, temperature and chemical potential. Using QME formalism, we obtain an analytical expression of the Berry-like phase for eigenstate of the QME in the parameter space. We show that the Berry-like curvature is non zero in the whole region in the parameter space. We also show that the Berry-like curvature vanishes in the case of single quantum dot and the case of isolated two dots.