  The interaction of intense laser pulses with nano-scale particles leads to
the production of high-energy electrons, ions, neutral atoms, neutrons and
photons. Up to now, investigations have focused on near-infrared to X-ray laser
pulses consisting of many optical cycles. Here we study strong-field ionization
of rare-gas clusters ($10^3$ to $10^5$ atoms) using two-cycle 1.8~$\mu$m laser
pulses to access a new interaction regime in the limit where the electron
dynamics are dominated by the laser field and the cluster atoms do not have
time to move significantly. The emission of fast electrons with kinetic
energies exceeding 3keV is observed using laser pulses with a wavelength of
1.8~$\mu$m and an intensity of $1\times 10^{15}$~W/cm$^2$, whereas only
electrons below 500eV are observed at 800nm using a similar intensity and pulse
duration. Fast electrons are preferentially emitted along the laser
polarization direction, showing that they are driven out from the cluster by
the laser field. In addition to direct electron emission, an electron
rescattering plateau is observed. Scaling to even longer wavelengths is
expected to result in a highly directional current of energetic electrons on a
few-femtosecond timescale.
