The missing memristor found

Memristance movement Basic electronics textbooks list three fundamental passive circuit elements: resistors, capacitors and inductors. But nearly forty years ago, Leon Chua predicted the existence of a fourth, the memristor — in effect a nonlinear resistor with memory. A paper from the Hewlett-Packard research lab now reports that memristance arises naturally in nanoscale systems where solid-state electronic and ionic transport are coupled under an external bias voltage. This finding can help explain many examples of apparently anomalous hysteretic current–voltage behaviour observed in electronic devices during the past 50 years. Memristors may have a significant impact on future electronic circuits by dramatically increasing the functional density over that achieved by transistors. There are three fundamental passive circuit elements, resistors, capacitors, and inductors, but it was reasoned that there should be a fourth fundamental element, called a memristor, which has until now not been realized in a physical system. A fresh analysis of the concept shows that memristance arises naturally in nanoscale systems where solid state electronic and ionic transport are coupled under an external bias voltage. Anyone who ever took an electronics laboratory class will be familiar with the fundamental passive circuit elements: the resistor, the capacitor and the inductor. However, 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) 1 . Although he showed that such an element has many interesting and valuable circuit properties, until now no one has presented either a useful physical model or an example of a memristor. Here we 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 behaviour observed in many nanoscale electronic devices 2 , 3 , 4 , 5 , 6 , 7 , 8 , 9 , 10 , 11 , 12 , 13 , 14 , 15 , 16 , 17 , 18 , 19 that involve the motion of charged atomic or molecular species, in particular certain titanium dioxide cross-point switches 20 , 21 , 22 .