Anderson localization of electrons in dense He4 gas
The conductance of a dilute 2D electron gas on hydrogen is measured as a function of ambient He4 gas density. At densities below 1020 cm-3 the electron scattering rate is the sum of a classical term linear in He4 density plus a He4-adsorbate-scattering term. Towards higher densities, however, the conductivity decreases exponentially which we attribute to strong localization of electrons below a threshold energy EckBT. We present an estimate of Ec based on weak-localization theory and find good agreement with both our 2D data and the 3D mobility measurements in the literature. In 3D, the Ioffe-Regel criterion for localization is found to be kl0=2.5±0.5. © 1988 The American Physical Society.