Surface Structure and Reconstructions of HgTe (111) Surfaces

HgTe (111) surface is comprehensively studied by scanning tunneling microscopy/spectroscopy (STS). In addition to the primitive (1\times 1) hexagonal lattice, six reconstructed surface structures are observed: (2\times 2), 2\times 1, 4\times 1, 3\times \sqrt3, 2\sqrt2\times 2 and \sqrt11\times 2. The (2\times 2) reconstructed lattice maintains the primitive hexagonal symmetry, while the lattices of the other five reconstructions are rectangular. Moreover, the topographic features of the 3\times \sqrt3 reconstruction are bias dependent, indicating that they have both topographic and electronic origins. The STSs obtained at different reconstructed surfaces show a universal dip feature with size \sim 100 mV, which may be attributed to the surface distortion. Our results reveal the atomic structure and complex reconstructions of the cleaved HgTe (111) surfaces, which paves the way to understand the rich properties of HgTe crystal.