Single electron tunneling

This is a brief review, of some recent developments in experiments and theo ry of the Coulomb blockade phenomenon. We concentrate on electron tunneling through semiconductor quantum dots and normal-metal nanoparticles. The lin ear conductance and non-linear I-V characteristics are sensitive not only t o the charging energy, but also to smaller energy scales. These are the spa cing between discrete energy levels of intra-dot electron excitations, and the width these levels acquire due to the electron escape to leads through the junctions. At sufficiently low temperatures, or at not-so-small junctio n conductances, the many-body phenomena, such as Kondo effect, become obser vable in the dot-lead system. Kondo effect yields an additional fine energy scale to the problem. We discuss a simple theoretical model incorporating these energy scales, and its I elation to the experimental observations. PA CS numbers: 73.23.-b, 73.23.Hk, 73.40.Gk.