Generation of an isolated dense attosecond electron beam in wakefields driven by a few-cycle laser pulse

Isolated attosecond electron beams with high charge density have significant applications in ultrafast science. However, the generation of such electron beams via laser wakefield acceleration remains a challenge today. Here, we present and numerically demonstrate a novel approach for generating isolated dense attosecond electron beams in wakefields driven by a joule-class few-cycle laser pulse in underdense plasma. Three-dimensional particle-in-cell simulations show that, with typical nowadays laser plasma parameters, an isolated attosecond electron beam can be obtained with a pulse duration of 118 as, a peak energy of 38.5 MeV, a charge of 45 pC, and a peak density of several times the critical density. Meanwhile, the robustness of this scheme has also been numerically verified. Such a scheme enables effective generation of isolated dense attosecond electron pulses, addressing critical requirements in attosecond physics applications.