Sunday, October 16, 2011
Condensed matter systems are complicated systems because they are ensemble of atoms and molecules held tight by inter-atomic and inter-molecular forces. The forces arise as a result of various interactions - interactions between electrons in neighboring atoms, dipole interactions, overlap of the wave functions, etc. A condensed matter system may also have defects and dislocations of various kinds. Therefore, studying the properties of condensed matter systems like a chunk of gold or a cup of water is not an easy subject.
Because of the discovery of new ideas and a rapid development of technology, there are a lot of new methods developed to study condensed matter systems. One such way is simulating condensed matter using an optical lattice. An optical lattice is a 'light crystal' formed by interfering laser light waves traveling in opposite directions. A pair of counter-propagating laser light waves form a standing wave - a wave with intensity maxima and minima at regular spatial intervals. This is a one dimensional optical lattice. Two orthogonal pairs of lasers form a sheet of optical lattice - a two dimensional structure. If three pairs of counter-propagating lasers along X-, Y- , and Z- directions interfere each other, they form a structure which is called a three dimensional optical lattice.
An optical lattice can be controlled as you wish, by varying the wavelength of the component lasers. What is an optical lattice good for? An optical lattice is a clean system - free of defects. It is tunable, controllable and easily manipulated as desired and required. An optical lattice can simulate a condensed matter system. How? In an optical lattice, there are arrays of regularly spaced sites of low potential which can be filled with atom(s). One can fill with similar or dissimilar atoms in the sites. Therefore, the optical lattice with atoms sitting in the potential minima simulates condensed matter systems.
A condensed matter system as it stands is 'GOD-MADE', and so it can not be manipulated easily. For example, you can not change the lattice constant or the coupling strength in a block of silver. Therefore, a system which may represent widely distributed condensed matter systems - ranging from a water molecule to the complex structure like a human brain is extremely important to understand the properties of the condensed matter, and ultimately the Universe !
Note: This posting is in progress. Your comments are highly appreciated !