Carrier-Envelope-Phase-Induced Asymmetries in Double Ionization of Helium by an Intense Few-Cycle XUV Pulse*

A complete formulation of the carrier-envelope-phase (CEP) dependence of electron angular distributions in double ionization of He by an arbitrarily-polarized, few-cycle, intense XUV pulse is carried out using perturbation theory (PT) in the pulse amplitude.\footnote{J.M. Ngoko Djiokap, N.L. Manakov, A.V. Meremianin and A.F. Starace, Phys.~Rev.~A~\textbf{88}, 053411 (2013).} The broad pulse bandwidth induces interference of first- and second-order PT amplitudes producing thus asymmetric angular distributions which can be controlled by the CEP of the pulse. For linear polarization of the pulse, our PT parametrization is in excellent agreement with results of solutions of the full-dimensional, two-electron time-dependent Schr\"{o}dinger equation, validating thus the PT approach.