Current flow around small polarons embedded in a Mott insulator

A doped hole in the parent compound of the superconducting cuprate is believed to form so-called, “Zhang–Rice Singlet” (ZRS). Recent theoretical calculations indicate that the ZRS causes local lattice deformation and the doped hole becomes a small polaron (pseudo Jahn–Teller polaron) that moves with large effective mass. The formation of pseudo Jahn–Teller polarons with large effective mass seems to contradict the observed small effective mass of the charge carrier (m∗/m ≈ 3); however, we argue that this contradiction is removed if the small polaron becomes a core of a meron (a vortex in spin configuration with winding number +1) or an antimeron (a vortex in spin configuration with winding number −1). We show that if polaronic cores of merons and antimerons are formed, electrons surrounding the cores become itinerant.