Designer photocurrents

When photons are absorbed by electrons in a material such as a semiconductor, the distribution of excited electrons in the Brillouin zone tends to be nonpolar, which corresponds to a vanishing electric current, as the carriers move in every direction. However, if two optical beams are used to excite carriers, different optical absorption processes can interfere constructively or destructively in different regions of the Brillouin zone, which can lead to a polar distribution. Quantum interference can thus be employed to control where in the Brillouin zone the carriers are injected, which can lead to large charge, spin, and valley photocurrents due to minimal numbers of excited carriers. In this talk I will present techniques for quantum interference control (QuIC) of photocurrents in different materials and discuss some of its applications in science and technology. For instance, QuIC can be used as "Brillouin zone tweezers" to study the properties of particular excited states of materials, and it can also be used in devices that integrate photonics to electronics, spintronicsĀ and valleytronics.