Quantum mechanics was developed in the early twentieth century to describe the motion of a single electron in a hydrogen atom. Later, Einstein and others pointed out that the quantum theory of a pair of electrons had non-intuitive features which they found unpalatable: two well-separatedelectrons can have their quantum states "entangled", indicating that they talk to each other quantum mechanically, even though they are far apart. Today, quantum entanglement is not viewed as a subtle microscopic effect of interest only to a few physicists, but as a crucial ingredient necessary for a complete understanding of the many phases of matter. A crystal can have roughly trillion trillion electrons entangled with each other, and the different patterns of entanglement lead to phases which are magnets, metals, or superconductors. I will give a simple discussion of these and other remarkable features of the quantum mechanics of a trillion trillion electrons, and of their importance to a variety of technologically important materials. The theory also has surprising and unexpected connections to string theory: remarkably, this connects the motion of electrons within a plane of a crystal in the laboratory, to the theory of astrophysical black holes similar to those studied by Chandrasekhar.
Subir Sachdev (Harvard University)
Date & Time
06 December 2010, 16:00 to 17:00
Faculty Hall, IISc, Bangalore