THE RELATION BETWEEN PEIERLS AND MOTT-HUBBARD TRANSITION IN VO_2 BY TUNNELING SPECTROSCOPY

摘要

Tunneling speclroscopy has been performed on W-doped VO_2 single crystal near the Metal-Insulator transition temperature. The tunneling energy gap was in good agreement with band calculations and optical measurements near the transition temperature. We have found by tunneling spectroscopy an additional density of states in the low-temperature phase. With increasing temperature. from room temperature to just below the transition temperature, an additional increase in the density or states was observed in the conduction band and it shifted downward to the bottom of conduction band. When the front of the additional density of states approaches the bottom of conduction band, edges of the tunneling energy gap becomes blurred, and the VO_2 lums into the high-temperature phase. A model for the mechanism of the Metal-Insulator transition in VO_2 is proposed.