The fourth element or the missing memristor

In 1971 Leon Chua reasoned from symmetry arguments that there should be a fourth fundamental element, which he called a memristor (short for memory resistor). Although he showed that such an element has many interesting and valuable circuit properties, until 2008 no one has presented either a useful physical model or an example of a memristor. In the paper in Nature (2008) the team of Stan Williams show, using a simple analytical example, that memristance arises naturally in nanoscale systems in which solid-state electronic and ionic transport are coupled under an external bias voltage. These results serve as the foundation for understanding a wide range of hysteretic current-voltage behavior observed in many nanoscale electronic that involve the motion of charged atomic or molecular species, in particular certain titanium dioxide cross-point switches. In the talk a brief overview of the memristors will be given and the potential applications will be presented. A promising application of memristor is based on its property to imitate natural nerves. Some research groups use such memristors as key components in a blueprint for an artificial brain. A memristor that is capable of learning will be considered at the end of the talk as well.