Physics of impurities in a Bose gas

• Applicant: Professor Dr. Hans-Werner Hammer, since 10/2019
• Subject Area: Optics, Quantum Optics and Physics of Atoms, Molecules and Plasmas ; Theoretical Condensed Matter Physics
• Term: from 2018 to 2022
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 413495248

• Final Report Year: 2023

Final Report Abstract

This project addressed the static and dynamic properties of quantum impurities in cold Bose gases. A convenient way to study such systems is to use the concept of the polaron – a quasiparticle that is often pictured as an impurity dressed with low-energy excitations (phonons) of the environment. The polaron problem is central to our understanding of certain semiconductors, high-temperature superconductors and many other materials. Its importance is well understood but its exact solution is still out of reach. Very recently, following the idea of analog quantum computation, these quasiparticles were created in cold bosonic gases. This experimental achievement provided a platform for testing various theoretical models and conceptual ideas; it deepens our understanding of paradigmatic condensed matter systems with impurities, and places the Bose polaron problem at the forefront of the physics of quantum gases. The main objective of this proposal was to expand our understanding of the physics of impurities in cold-atom experiments. In particular, we have investigated the time dynamics of impurities in onedimensional harmonically-trapped Bose gases, emergent impurity-impurity interactions, and the possibility to measure properties of the environment using the impurity as a probe.

Publications

• Effective approach to impurity dynamics in one-dimensional trapped Bose gases. Physical Review A, 100(1).
  Mistakidis, S. I.; Volosniev, A. G.; Zinner, N. T. & Schmelcher, P.
  
• Engineering momentum profiles of cold-atom beams. Physical Review A, 100(3).
  Smith, D. Hudson & Volosniev, Artem G.
  
• In-medium bound states of two bosonic impurities in a one-dimensional Fermi gas. Physical Review Research, 1(3).
  Huber, D.; Hammer, H.-W. & Volosniev, A. G.
  
• Induced correlations between impurities in a one-dimensional quenched Bose gas. Physical Review Research, 2(2).
  Mistakidis, S. I.; Volosniev, A. G. & Schmelcher, P.
  
• Impurities in a one-dimensional Bose gas: the flow equation approach. SciPost Physics, 11(1).
  Brauneis, Fabian; Hammer, Hans-Werner; Lemeshko, Mikhail & Volosniev, Artem
  
• Morphology of three-body quantum states from machine learning. New Journal of Physics, 23(6), 065009.
  Huber, David; Marchukov, Oleksandr V.; Hammer, Hans-Werner & Volosniev, Artem G.
  
• Shape of a sound wave in a weakly-perturbed Bose gas. SciPost Physics, 10(2).
  Marchukov, Oleksandr & Volosniev, Artem
  
• Artificial atoms from cold bosons in one dimension. New Journal of Physics, 24(6), 063036.
  Brauneis, Fabian; Backert, Timothy G.; Mistakidis, Simeon I.; Lemeshko, Mikhail; Hammer, Hans-Werner & Volosniev, Artem G.
  
• Emergence of a Bose polaron in a small ring threaded by the Aharonov-Bohm flux. Communications Physics, 6(1).
  Brauneis, Fabian; Ghazaryan, Areg; Hammer, Hans-Werner & Volosniev, Artem G.