Bose Polarons at Finite Temperature and Strong Coupling

Area of Science:

• Quantum physics
• Ultracold atomic gases
• Bose-Einstein condensation

Background:

• A Bose polaron is a mobile impurity interacting with a Bose gas.
• At zero temperature, a single attractive quasiparticle is known to exist.
• Understanding polaron behavior at finite temperatures is crucial.

Purpose of the Study:

• To investigate the spectral properties of Bose polarons at finite temperatures.
• To determine how the impurity-boson interaction strength affects the polaron spectrum.
• To explore the temperature dependence of polaron quasiparticles.

Main Methods:

• Theoretical analysis of a mobile impurity in a Bose gas.
• Examination of the system's behavior at finite temperatures (T > 0).
• Focus on the role of impurity-boson interaction strength and Bose-Einstein condensation critical temperature (Tc).

Main Results:

• The Bose polaron spectrum splits into two quasiparticles at finite temperatures for strong interactions.
• The ground state quasiparticle energy is minimized at Tc and becomes overdamped at T >> Tc.
• A higher-energy quasiparticle exists only below Tc, mixing the impurity with Bogoliubov modes.

Conclusions:

• The spectral splitting of Bose polarons is a finite-temperature phenomenon dependent on interaction strength.
• This behavior is not limited to ultracold gases and applies to other systems with gapless bosonic modes.
• The study reveals complex quasiparticle dynamics in interacting quantum gases.