Statistical physics of artificial continuously tunable lattices of 2d and 3d trapped identical particles

optical-lattice


One goal of statistical mechanics is to understand how macroscopic properties arise from the interactions of microscopic components. Until about fifteen years ago, scientists interested in the macroscopic properties of metals, magnets, superconductors, and other structures had to rely on the ingenuity (and luck) of crystal growers to synthesize novel materials that had interesting properties. While thermodynamic parameters of the crystal could be varied, it was generally not possible to change the interactions between particles or their lattice spacing, which made comparison with theory difficulty.

Physicists have since developed the remarkable ability to use interfering laser beams to create 1d, 2d, and 3d periodic lattices of trapped ions or atoms (shown in the above figure) that could be bosons or fermions or a mixture, and so create artificial materials where microscopic details like the lattice spacing or interactions between the trapped particles could be varied continuously, which greatly increased the ability of experimentalists to explore new kinds of phenomena and to compare experiments with theory. These experiments are an example of 21st century experimental statistical physics, in which remarkable control of microscopic details can be achieved for novel macroscopic substances.

An example of a major scientific advance using this method was the first successful trapping in a three-dimensional cubic lattice of fermions (potassium 40K atoms) in 2008, that allowed the experimental group to study the phase transition of an insulator to a metal by adjusting the lattice spacing directly. See the paper R. Jordens et al, "A Mott insulator of fermionic atoms in an optical lattice", Nature 455:207 (2008).

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