Attractive and repulsive Fermi polarons in two dimensions

Abstract

The dynamics of a single impurity in an environment is a fundamental problem in many-body physics. In the solid state, a well-known case is an impurity coupled to a bosonic bath, for example lattice vibrations. Here the impurity together with its accompanying lattice distortion form a new entity, a polaron. This quasiparticle plays an important role in the spectral function of high-Tc superconductors as well as in colossal-magnetoresistance in manganites. For impurities in a fermionic bath, the attention so far has been mostly on heavy or immobile impurities which exhibit Anderson's orthogonality catastrophe and the Kondo effect. Only recently, mobile impurities have moved into the focus of research and they have been found to form new quasiparticles, so called Fermi polarons. The Fermi polaron problem constitutes the extreme, but conceptually simple, limit of two important quantum many-body problems: the BEC-BCS crossover with spin-imbalance for attractive interactions and Stoner's itinerant ferromagnetism for repulsive interactions. It has been proposed that this and other yet elusive exotic quantum phases might become realizable in Fermi gases confined to two dimensions. Their stability and observability is intimately related to the theoretically debated properties of the Fermi polaron in two dimensional Fermi gas. Here we create and investigate these Fermi polarons and measure their spectral function using momentum-resolved photoemission spectroscopy. For attractive interactions we find evidence for the disputed pairing transition between polarons and tightly bound dimers, which provides insight into the elementary pairing mechanism of imbalanced, strongly-coupled two-dimensional Fermi gases. Additionally, for repulsive interactions we study novel quasiparticles, repulsive polarons, whose lifetime determine the possibility of stabilizing repulsively interacting Fermi systems.

References in corpus (12)

• Many-Body Physics with Ultracold Gases
• Observation of Fermi Polarons in a Tunable Fermi Liquid of Ultracold Atoms
• Using photoemission spectroscopy to probe a strongly interacting Fermi gas
• Fermi-Polaron: Diagrammatic Monte Carlo for Divergent Sign-Alternating Series
• Normal state of a polarized Fermi gas at unitarity
• Radiofrequency spectroscopy of a strongly interacting two-dimensional Fermi gas
• Ultra-cold Polarized Fermi Gases
• Excitation spectra and rf-response near the polaron-to-molecule transition from the functional renormalization group
• Measuring the one-particle excitations of ultracold fermionic atoms by stimulated Raman spectroscopy
• Polaron-molecule transitions in a two-dimensional Fermi gas
• Polarons and Molecules in a Two-Dimensional Fermi Gas
• Superfluidity at the BEC-BCS crossover in two-dimensional Fermi gases with population and mass imbalance

Cited by in corpus (46)

• Repulsive Fermi polarons in a resonant mixture of ultracold ${}^6$Li atoms
• Homogeneous Atomic Fermi Gases
• Time dependent impurity in ultracold fermions: orthogonality catastrophe and beyond
• Holographic Polarons, the Metal-Insulator Transition and Massive Gravity
• Observation of pair condensation in the quasi-2D BEC-BCS crossover
• Variational study of polarons in Bose-Einstein condensates
• Highly polarized Fermi gases in two dimensions
• Numerical analytic continuation: Answers to well-posed questions
• Spin-Imbalanced Quasi-Two-Dimensional Fermi Gases
• Quantum Monte-Carlo study of the Bose polaron problem in a one-dimensional gas with contact interactions
• Polarons in Ultracold Fermi Superfluids
• Polaronic atom-trimer continuity in three-component Fermi gases
• Quantum Breathing of an Impurity in a One-dimensional Bath of Interacting Bosons
• Finite-temperature behavior of the Bose polaron
• A two-dimensional Fermi liquid with attractive interactions
• Quantum critical transport in the unitary Fermi gas
• Quantum Brownian Motion with Inhomogeneous Damping and Diffusion
• Bloch oscillations of bosonic lattice polarons
• Observation of interspecies Feshbach resonances in an ultracold ${}^{39}$K-${}^{133}$Cs mixture and refinement of interaction potentials
• Molecule and polaron in a highly polarized two-dimensional Fermi gas with spin-orbit coupling
• Shear viscosity and spin diffusion in a two-dimensional Fermi gas
• Diagrammatic Monte Carlo study of quasi-two-dimensional Fermi-polarons
• Universality of weakly bound dimers and Efimov trimers close to Li-Cs Feshbach resonances
• Enhancing the Efimov correlation in Bose polarons with large mass imbalance
• The p-wave polaron
• Three-component Ultracold Fermi Gases with Spin-Orbit Coupling
• Three-body problem in a two-dimensional Fermi gas
• Polarons and Molecules in a Fermi Gas with Orbital Feshbach Resonance
• Radio frequency spectra of Feshbach molecules in quasi-two dimensional geometries
• Two-dimensional short-range interacting attractive and repulsive Fermi gases at zero temperature
• Pairing and radio-frequency spectroscopy in two-dimensional Fermi gases
• Hartree-Fock treatment of Fermi polarons using the Lee-Low-Pine transformation
• Radio-frequency spectroscopy of weakly bound molecules in spin-orbit coupled atomic Fermi gases
• Momentum-resolved radio-frequency spectroscopy of a spin-orbit coupled atomic Fermi gas near a Feshbach resonance in harmonic traps
• Momentum-resolved spectroscopy of a Fermi liquid
• Universal trimers emerging from a spin-orbit coupled Fermi sea
• Angular self-localization of impurities rotating in a bosonic bath
• Repulsive Fermi polarons with negative effective mass
• Coupled Ferromagnetic and Nematic Ordering of Fermions in an Optical Flux Lattice
• Interaction energy and itinerant ferromagnetism in a strongly interacting Fermi gas in the absence of molecule formation
• The self-energy of an impurity in an ideal Fermi gas to second order in the interaction strength
• A mixed dimensional Bose polaron
• Periodically-driven Kondo impurity in nonequilibrium steady states
• Mobile Impurities and Orthogonality Catastrophe in two-dimensional Vortex Lattices
• One-Dimensional Quantum Systems - From Few to Many Particles
• Kondo dynamics in one-dimensional doped ferromagnetic insulators