Abstract
A Van Hove singularity (VHS) is a singularity in the phonon or electronic density of states of a crystalline solid. When the Fermi energy is close to the VHS, instabilities will occur, which can give rise to new phases of matter with desirable properties. However, the position of the VHS in the band structure cannot be changed in most materials. In this work, we demonstrate that the carrier densities required to approach the VHS are reached by gating in a suspended carbon nanotube Schottky barrier transistor. Critical saddle points were observed in regions of both positive and negative gate voltage, and the conductance flattened out when the gate voltage exceeded the critical value. These novel physical phenomena were evident when the temperature is below 100 K. Further, the temperature dependence of the electrical characteristics was also investigated in this type of Schottky barrier transistor.
Highlights
Single-walled carbon nanotubes (SWNTs) are quasi-onedimensional (1D) materials with semiconducting or metallic properties that make them attractive for both fundamental science and technology [1,2,3]
We report a clear signature of Van Hove singularity (VHS) in the conductance versus gate voltage of Schottky barrier transistors with individual suspended SWNTs
Critical saddle points were observed in regions of both positive and negative gate voltage, and the conductance flattened out when the gate voltage exceeded the critical value
Summary
Single-walled carbon nanotubes (SWNTs) are quasi-onedimensional (1D) materials with semiconducting or metallic properties that make them attractive for both fundamental science and technology [1,2,3]. When the Fermi energy (EF) is close to the VHS, instabilities and divergences in the DOS occur, which can lead to the emergence of new phases of matter, such as superconductivity or magnetism [12, 13] This suggests the possibility of engineering the material properties by modulating EF and the VHS together. We report a clear signature of VHSs in the conductance versus gate voltage of Schottky barrier transistors with individual suspended SWNTs. Critical saddle points were observed in regions of both positive and negative gate voltage, and the conductance flattened out when the gate voltage exceeded the critical value. Critical saddle points were observed in regions of both positive and negative gate voltage, and the conductance flattened out when the gate voltage exceeded the critical value These novel physical phenomena were confirmed when the temperature is below 100 K. The temperature dependence of the electrical characteristics was demonstrated in this type of Schottky barrier transistor
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