Imaging nano-scale electronic inhomogeneity in lightly doped Mott insulator Ca_{2-x}Na_{x}CuO_{2}Cl_{2}

TL;DR

This study used STM/STS to image nano-scale electronic inhomogeneity in lightly doped Ca_{2-x}Na_{x}CuO_{2}Cl_{2}, revealing domains that are crucial for understanding the insulator-metal transition in Mott insulators.

Contribution

First direct imaging of nano-scale electronic domains in lightly doped Ca_{2-x}Na_{x}CuO_{2}Cl_{2} using STM/STS, highlighting their role in the insulator-metal transition.

Findings

Nano-scale domains (~2 nm) with high local density of states observed.

Domains have preferred orientations along the tetragonal [100] direction.

Electronic inhomogeneity is inherent to lightly doped Mott insulators.

Abstract

The spatial variation of electronic states was imaged in the lightly doped Mott insulator Ca_{2-x}Na_{x}CuO_{2}Cl_{2} using scanning tunneling microscopy / spectroscopy (STM/STS). We observed nano-scale domains with a high local density of states within an insulating background. The observed domains have a characteristic length scale of 2 nm (~4-5a, a:lattice constant) with preferred orientations along the tetragonal [100] direction. We argue that such spatially inhomogeneous electronic states are inherent to slightly doped Mott insulators and play an important role for the insulator to metal transition.