Quantum features in atomic nanofabrication using exactly resonant standing waves.

We report on the first fabrication of nanostructures with exactly resonant light revealing the quantum character of the atom-light interaction. Classically the formation of nanostructures is not expected; thus, the observed formation of complex periodic line patterns can be explained only by treating atom-light interaction and propagation of the atoms quantum mechanically. Our numerical quantum calculations are in quantitative agreement with this experimental finding. Moreover, the theory predicts that for small detunings nanostructures with ?/4 period can be produced, which beats the standard nanofabrication limit of ?/2. Our experiments confirm this prediction.