Ultrafast quenching of binary colloidal suspensions in an external magnetic field.

An ultrafast quench is applied to binary mixtures of superparamagnetic colloidal particles confined at a two-dimensional water-air interface by a sudden increase of an external magnetic field. This quench realizes a virtually instantaneous cooling which is impossible in molecular systems. Using real-space experiments, the relaxation behavior after the quench is explored.

Binary crystals in two-dimensional two-component Yukawa mixtures.

The zero-temperature phase diagram of binary mixtures of like-charge particles interacting via a screened Coulomb pair potential is calculated as a function of composition and charge ratio. The potential energy obtained by a Lekner summation is minimized among a variety of candidate two-dimensional crystals. A wealth of different stable crystal structures is identified including A, B, AB(2), A(2)B, and AB(4) structures [A (B) particles correspond to large (small) charge.