Sibin Yang: Single-hole spectral function of the t-J-Q model

Abstract: I investigate the single-hole spectral function A(k,w) of a two-dimensional quantum magnet that can be driven through a quantum phase transition from an antiferromagnetic (AFM) to spontaneously dimerized valence-bond solid (VBS) ground state. Results are obtained using stochastic analytic continuation of imaginary-time data from quantum Monte Carlo simulations. I first present results in the (AFM) phase and benchmark them against previous results. The optimal spin-polaron quasiparticle weight is extracted in a more reliable way than in past studies. I then explore the system at the quantum critical point between the AFM and VBS phases, where the calculations show the emergence of fractionalized excitations. I analyze spinon deconfinement and spin–charge separation through a combined study of the single-hole spectral function the dynamic spin structure factor. Finally, deep in the VBS phase, my results show that the dispersion minimum of the quasiparticle (spin polaron) shifts away from its location at k=(\pi/2, \pi/2) in the AFM phase, as predicted in field-theory studies but never before observed on the lattice.