Collapse of the Mott Gap and Emergence of a Nodal Liquid in Lightly Doped Sr2IrO4

Abstract

We report angle resolved photoemission experiments on the electron doped Heisenberg antiferromagnet (Sr1-xLax)2IrO4. For a doping level of x=0.05, we find an unusual metallic state with coherent nodal excitations and an antinodal pseudogap bearing strong similarities with underdoped cuprates. This state emerges from a rapid collapse of the Mott gap with doping resulting in a large underlying Fermi surface that is backfolded by a (π,π) reciprocal lattice vector which we attribute to the intrinsic structural distortion of Sr2IrO4.