Creation of Rydberg Polarons in a Bose Gas

Area of Science:

• Atomic physics
• Quantum mechanics
• Condensed matter physics

Background:

• Polarons are quasiparticles formed when an impurity interacts with the surrounding medium.
• Rydberg atoms, highly excited atoms, can form polarons when introduced into quantum gases.
• Strontium Bose-Einstein condensates provide a unique environment for studying polaron formation due to specific scattering properties.

Purpose of the Study:

• To spectroscopically observe and characterize Rydberg polarons in a strontium Bose gas.
• To investigate the influence of strontium's unique scattering properties on polaron behavior.
• To analyze the formation and spectral features of molecular Rydberg states associated with these polarons.

Main Methods:

• Spectroscopic observation of Rydberg atoms excited within a strontium Bose-Einstein condensate.
• Utilizing a functional determinant approach (FDA) to model the polaron system.
• Solving an extended Fröhlich Hamiltonian to describe a mobile impurity in a Bose gas.

Main Results:

• Observation of Rydberg polarons with macroscopic occupation of bound molecular states.
• Identification of universal behavior in Rydberg spectral line shape and spectral width scaling.
• Experimental resolution and accurate reproduction of excited states of polyatomic Rydberg molecules (trimers, tetrameters, pentamers).

Conclusions:

• The absence of p-wave resonance in Sr leads to universal spectral properties of Rydberg polarons.
• The functional determinant approach accurately describes the observed spectral features and molecular states.
• This work provides new insights into polaron physics in quantum gases and the formation of Rydberg molecules.