Electronic structure in a transition metal dipnictide TaAs₂

Area of Science:

• Condensed Matter Physics
• Materials Science
• Topological Materials

Background:

• Transition-metal dipnictides are known for topological states and large magnetoresistance (MR).
• Tantalum diarsenide (TaAs2) was theoretically predicted to exhibit a topological crystalline insulating state.

Purpose of the Study:

• To experimentally investigate the electronic structure and transport properties of TaAs2.
• To determine the origin of the extreme magnetoresistance in TaAs2.
• To clarify the topological nature of TaAs2 surfaces.

Main Methods:

• High-resolution angle-resolved photoemission spectroscopy (ARPES) to probe the Fermi surface (FS) and electronic bands.
• Magneto-transport measurements to observe magnetoresistance.
• First-principles electronic structure computations for comparison with experimental data.

Main Results:

• ARPES revealed both closed and open pockets in the metallic Fermi surface of TaAs2.
• Linearly dispersive bands were observed on the (2‾01) surface.
• Extreme magnetoresistance was confirmed through transport measurements.
• The observed surface bands were identified as trivial bulk bands, indicating a topologically dark (2‾01) surface.

Conclusions:

• The (2‾01) surface of TaAs2 does not host symmetry-protected topological surface states.
• The presence of open Fermi surface pockets is a key factor contributing to the observed extreme magnetoresistance.
• TaAs2 presents an interesting platform for studying the interplay between Fermi surface topology and large magnetoresistance.