Quantum Capacitance: A Perspective from Physics to Nanoelectronics

All materials (including conductors) possess the so-called quantum capacitance, which is present in series with the traditional geometric (electrostatic) capacitance. It is usually a large positive quantity and therefore irrelevant for most materials except for nanostructures. Quantum capacitance has been found to reduce the overall capacitance of nanostructures compared with what is predicted by classical electrostatics. One of many tantalizing recent physical revelations about quantum capacitance is that it can posses a negative value, hence, allowing for the possibility of enhancing (sometimes dramatically) the overall capacitance in some particular material systems—beyond the scaling predicted by classical electrostatics. We provide here a short overview of this subject and review some recent developments.