Scanning the Issue

The three basic electrical circuit elements, namely, capacitor, which was invented by Ewald Georg von Kleist in 1745, resistor, which was invented by Georg Simon Ohm in 1827, and inductor, which was invented by Michael Faraday in 1831, were constructed by experimental physicists to observe the lumped behavior of relevant measurable electrical parameters across the devices. In 1971, Leon Chua postulated the fourth basic circuit element while trying to establish a missing constitutive relationship between the electrical charge and the magnetic flux. Using Lewis Carroll’s portmanteau naming technique, Chua named this hypothetical nonlinear device, memristor (memory + resistor) since it demonstrated the hysteresis property of the-then ferromagnetic core memory and also the dissipative characteristics of a resistor. Clearly, in such devices, the nonlinear resistance can be memorized indefinitely by controlling the flow of the electrical charge or the magnetic flux. In 1976, Leon Chua and Sung Mo Kang further extended the concept of memristor by proposing a broader class of memristive devices and systems. Though there were initial attempts to validate Chua’s theoretical postulation of memristor by demonstrating the charge-controlled memristor behavior with the help of active and passive electrical circuit components, during these intervening years, practicing design engineers did not pay much attention to apply the memristors in commercial products because of the complexity involved in implementing memristors. As a result, the direct physical realization of memristor as the fourth basic circuit element remained unresolved, de facto forgotten for almost the past four decades. It was only in early 2008 when the Hewlett Packard (HP) researchers serendipitously observed the memristive behavior of nanoscale cross-point devices in their crossbar memory arrays and credited the seminal work of Leon Chua published in 1970s to the nanoscale phenomenon they witnessed, that the entire electrical and computer engineering community was galvanized by the reemergence of the missing memristor as a fundamental circuit element since it kicked open new vistas in multiple frontiers ranging from the abstruse chaos theory to nanoscale commercial products. This new technology is expected to bring about a slew of inventions in nonlinear dynamics of mem-impedance circuitry, programmable Boolean circuits, neuromorphic system design, transistorless multilevel nonvolatile digital memories, and so on. In less than two years since the HP paper appeared in Nature, the research output on memristors and memristive devices has grown exponentially with This issue covers five important aspects of memristor technology: theory, device engineering, circuit modeling, digital and analog systems, and neuromorphic systems.