Rotational meson resonances in Raman-ARPES spectra of doped antiferromagnets

The pseudogap phase in cuprate compounds remains poorly understood. While a decades-old idea attributes it to an underlying fractionalization of electrons into spinons and chargons, recent work points to the existence of a fractionalized Fermi liquid (FL*), where deconfined spinons and chargons form a meson-like bound state. Here we report direct numerical evidence for this bound state and its internal rotational excitations in the 2D t-J model doped with a single hole. We propose a combined Raman-ARPES protocol which allows to spectroscopically resolve non-trivial rotational resonances which are invisible in traditional ARPES spectra. Experimentally, we propose to drive a d-wave symmetric B_1g phonon mode and study multi-photon resonances in the ARPES spectrum. In our state-of-the-art time-dependent DMRG calculations we reveal a pronounced new rotational quasiparticle peak at low energies, in a regime where the traditional ARPES spectra is featureless. We explain the observed peak, as well as its dependence on the super-exchange energy J/t, by a simplified toy model where spinons and chargons are connected by a geometric string of displaced spins.