Quasiparticles Caught In Real Time

Scientists have used ultracold quantum gasses to make quasiparticles slow down enough to be observed.

AsianScientist (Oct. 19, 2016) – An international research team has observed the formation of quasiparticles in real time, a finding of global significance which holds major implications for the electronics industry. The research was published in Science.

When an electron moves in a solid, it produces a polarization due to its electrical charge. This ‘polarization cloud’ moves along with the electron, and together, these can theoretically be described as an independent quasiparticle. The present study features a new theoretical model to investigate quasiparticle formation, developed by physicists Drs. Meera Parish and Jesper Levinsen from Monash University in Australia.

“It’s like a skier in powder snow,” explained Professor Rudolf Grimm, who led the experimental investigation at the University of Innsbruck in Austria. “The skier is enveloped by a cloud of snow crystals. Together, they form a system with different properties than the skier without the snow cloud.”

However, measuring the formation of quasiparticles in solids represents a major challenge. According to Grimm, these processes take place in the attosecond (10−18 of a second) range and their time-resolved observation is extremely difficult.

To get around this problem, the researchers simulated the same physical processes at a much lower density by using ultracold quantum gases. These gases are an ideal testing ground to study physical phenomena that occur in solid-state materials and other states of matter, such as neutron stars. In such gases, quantum states of many particles can be engineered and the interaction between the particles precisely manipulated. In this setup, the resulting emergence of quasiparticles lasted a few microseconds.

“The observation of quasiparticle formation, virtually in real time, has fascinating implications,” said Parish. “It can help us to better understand ultrafast quantum processes which can ultimately be harnessed in a new generation of electronic devices.”

The article can be found at: Cetina et al. (2016) Ultrafast Many-body Interferometry of Impurities Coupled to a Fermi Sea.


Source: Monash University; Photo: IQOQI/Harald Ritsch.
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