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Scientific Highlight - January

Life and death of the Bose polaron.

Scientific Highlights - Melting Pot
Scientific Highlights - Melting Pot
By Shaeema Zaman at Science Melting Pot.
By Shaeema Zaman at Science Melting Pot.

In a recent paper by Magnus G. Skou et al. in Physical Review Research, physicists Jan J. Arlt and colleagues from the Department of Physics and Astronomy, Aarhus University studied the dynamics of the Bose polaron. Skou et al.’s research give an in-depth study of the dynamics of the so-called Bose polaron that provides the foundation for studying polaron models in general, which have applications in many fields, such as designing and engineering better materials. 

The study of quasiparticles through quantum simulation is an exciting and upcoming field of research. A quasiparticle is a physical concept, which treats elementary excitations (e.g. the quantum of energy of some vibration) as particles. Since such particles do not consist of matter, they are called quasiparticles. The polaron is a particularly important quasiparticle which arises when an electron moves through a solid material attracting nearby atoms in the crystal lattice of the material, which causes these nearby atoms to vibrate. A polaron’s mobility or effective mass can be quite different from that of the electron, changing the electrical and thermal transport properties of the material significantly. There are theoretical models that describe polarons but the challenge is that even these models are often too complex to be solved analytically. Hence, researchers are attempting to explore polaron physics using analogue systems made of ultracold atomic gases. An example of such a system is the work by Magnus G. Skou et al., where an impurity was created inside a Bose-Einstein condensate of potassium atoms. They created this impurity by using a radio frequency pulse to excite a small fraction of potassium atoms in another spin state, which allows them to behave as impurities. The impurity interacts with the condensate in a way that is similar to an electron in a crystal, giving rise to the Bose polaron. By using analogue systems, researchers can confirm the approximations made in polaron models as well as provide insights into the underlying physics. 

In this study, Magnus G. Skou et al. have provided an in-depth study of the dynamics of the Bose polaron using spectroscopic and interferometric measurements, which confirm theoretical predictions. Experimentally, these measurements are done using radio-frequency pulse sequences, which enable researchers to determine the energy of the polaron states from spectroscopy and their dynamical evolution from interferometry. 

Read the paper.

Other references: 

  1. https://physics.aps.org/articles/v9/86
  2. https://www.uni-muenster.de/Physik.AP/Demokritov/en/Forschen/Forschungsschwerpunkte/mBECwaqp.html
  3. https://www.nature.com/articles/s41567-021-01184-5#Sec2