Scanning Tunneling Microscopy of Defect-Induced Superstructure in 2H-NbSe$_{2}$

Scanning tunneling microscopy and spectroscopy measurements were performed on pure 2H-NbSe$_{2}$ with defects introduced by tip-sample interaction at 4K. Domains of a new superstructure with a lattice constant equals $\sqrt {13} $a$_{0}$ instead of 3a$_{0}$ were observed around the defects. Closer to the defects we also observed the disordered phase of this structure. Both of them are stable under the STM measurements at 4K. Atomically resolved microscopy and spectroscopy studies suggest a 2H to 1T phase transition induced by surface atom sliding.