Freiburg 2024 – scientific programme

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Q: Fachverband Quantenoptik und Photonik

Q 65: Ultra-cold Atoms, Ions and BEC V (joint session A/Q)

Q 65.6: Talk

Friday, March 15, 2024, 15:45–16:00, HS 1010

Magnetic polarons beyond linear spin-wave theory: Mesons dressed by magnons — •Pit Bermes and Fabian Grusdt — LMU Munich & MCQST, Munich, Germany

When a mobile impurity is doped into an antiferromagnet, its movement will distort the surrounding magnetic order and yield a magnetic polaron. The resulting complex interplay of spin and charge degrees of freedom gives rise to very rich physics and is widely believed to be at the heart of high-temperature superconductivity in cuprates. Recent experimental realizations of the doped Fermi-Hubbard model in ultra-cold quantum gases allowed to probe the local structure of the polarons. Drawing from experimental insights, we present a new quantitative theoretical formalism to describe these quasiparticles in the strong coupling regime. Based on the phenomenological parton description and geometric string picture, we construct an effective Hamiltonian with weak coupling to the spin-wave excitations in the background, making the use of standard polaronic methods possible.

We apply our formalism to calculate beyond linear spin-wave spectra, analyze the pseudogap expected at low doping and resolve the difference between hole an electron doping on local correlations.

Keywords: Hubbard model; Bose polaron; Cuprates; Doped Mott insulator