Two-Dimensional Conical Dispersion in ZrTe_{5} Evidenced by Optical Spectroscopy

Area of Science:

• Condensed Matter Physics
• Materials Science
• Solid State Physics

Background:

• Zirconium pentatelluride (ZrTe5) was recently proposed as a 3D Dirac semimetal.
• This classification was based on a single conical band at the Brillouin zone center.
• The lack of symmetry protection for this band raised questions about potential band gap opening and topological properties.

Purpose of the Study:

• To investigate the electronic band structure of ZrTe5.
• To determine if Zr5Te5 behaves as a 3D Dirac semimetal.
• To clarify the nature of electronic states and band dispersion in ZrTe5.

Main Methods:

• Combined experimental study using optical and transport measurements.
• Analysis of electronic band dispersion in ZrTe5.

Main Results:

• The electronic band dispersion in ZrTe5 is approximately linear only in the a-c plane.
• The band dispersion is relatively flat and parabolic along the b axis.
• A band gap of 2Δ=6 meV was observed at low temperatures.

Conclusions:

• The electronic states in ZrTe5 cannot be described by the 3D Dirac massless electron model.
• The observed band structure deviates from the predictions for a 3D Dirac semimetal.
• ZrTe5 exhibits anisotropic electronic properties, with distinct dispersion characteristics along different crystallographic axes.