| We study the semiclassical dynamics of a forced cold atom beam in a two-dimensional optical lattice, and show that the transverse displacement during a Bloch oscillation period is given by a winding integral on the quasi-momentum 2-torus. The difference between two such displacements is then shown to be equal to the integrated curvature of the energy band dispersion function, that can in turn be measured by subjecting the beam to a cold atom beam splitter, followed by time-of flight interferometry. For separable potentials the displacement vanishes, and the system becomes a coupled loop interferometer sensitive to the geometric (Berry-Wilkinson) phase of the energy band. |
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