Ab initio Lattice Results for Fermi Polarons in Two Dimensions

Area of Science:

• Quantum physics
• Condensed matter physics

Background:

• The Fermi polaron problem describes a quantum system with one impurity interacting with a sea of fermions.
• Understanding this problem is crucial for various fields, including ultracold atomic gases and condensed matter systems.

Purpose of the Study:

• To investigate the attractive Fermi polaron problem in two dimensions using nonperturbative methods.
• To introduce and validate a novel computational technique for simulating such systems.

Main Methods:

• Development and application of the impurity lattice Monte Carlo (ILMC) method, a new nonperturbative algorithm.
• Benchmarking the ILMC method by calculating the polaron energy in three dimensions in the unitarity limit.
• Performing the first fully nonperturbative calculations of polaron energy and density correlations in two dimensions.

Main Results:

• The ILMC method demonstrates computational efficiency and minimal sign oscillations for single-impurity systems.
• Calculations in three dimensions show agreement with established results, validating the method.
• The study provides the first nonperturbative results for two-dimensional Fermi polarons, including density correlations.
• Evidence for a smooth crossover transition between fermionic quasiparticle and molecular states was observed as interaction strength varied.

Conclusions:

• The developed ILMC method is a powerful tool for studying Fermi polarons.
• The research provides new insights into the behavior of two-dimensional Fermi polarons, particularly the transition to molecular states.