University of California, San Diego (UCSD) Physicists have identified new patterns that can determine the properties of a new state of matter.
In the journal Nature issue released on March 29, the scientists have illustrated that the cooling of excitons to near absolute zero will lead to the occurrence of ‘spin textures’, ‘spontaneous coherence,’ and ‘phase singularities’. However, a new state of matter will spontaneously be generated, which was scrutinized and evaluated at a temperature of only one-tenth of a degree above absolute zero by the physicists at UC San Diego.
In 2002, Professor Leonid Butov found that by bringing the excitons to a cold temperature, the excitons self-organize into a controlled array of microscopic droplets. Directed by Butov, the research team obtained 10x colder temperatures than previous experiments by using an advanced refrigerated system and calculated the coherence and spin of each bead with the help of an interferometer.
The researchers found that in space, the spinning of exciton particles is not homogeneous. Patterns called spin textures are formed around these beads. In addition, within the coherent exciton gas, a pattern of spontaneous coherence is associated with a pattern of spin polarization and phase singularities.
The excitons were produced by shining a laser on gallium arsenide samples that were cooled. The electrons are emitted out of the atomic orbitals through this laser light, thereby creating a positively charged hole and a negatively charged free electron. However, there is possibility of annihilation.
In order to control this annihilation, the research team created quantum wells to separate electrons and their holes, leading to generation of excitons having lifetime up to 50 ns.
During the experiments, the emission was made to pass through an interferometer that enabled the comparison of two spatially separated regions existing in the same sample. The researchers observed an improved spontaneous coherence in excitons.
Source: http://www.ucsd.edu/