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Anomalous electronic structure and magnetoresistance in TaAs2
Yongkang Luo1, R D McDonald1, P F S Rosa1
1Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA.
Scientific Reports
|June 9, 2016
Summary
The non-magnetic semimetal TaAs2 exhibits significant negative magnetoresistance, challenging existing theories. This discovery suggests new scattering mechanisms are responsible, not just Dirac/Weyl fermions.
Area of Science:
- Condensed Matter Physics
- Materials Science
- Quantum Materials
Background:
- Material resistance changes in magnetic fields, reflecting electronic states.
- Negative magnetoresistance (NMR) occurs in specific materials like semimetals or those with spin-disorder scattering.
- Existing theories often link NMR to Dirac/Weyl electronic structures.
Purpose of the Study:
- Investigate the mechanism behind the large negative magnetoresistance in the non-magnetic semimetal TaAs2.
- Determine the topological properties and electronic structure of TaAs2.
- Clarify the relationship between topological properties and negative magnetoresistance.
Main Methods:
- Experimental measurement of magnetoresistance in TaAs2.
- Density functional theory (DFT) calculations.
- Topological invariant calculations (ℤ2 invariant).
Main Results:
- TaAs2 exhibits a very large negative magnetoresistance.
- DFT calculations reveal TaAs2 as a topological semimetal with a ℤ2 invariant of (0;111).
- TaAs2 lacks Dirac dispersion, indicating NMR is not solely due to chiral anomaly from Dirac/Weyl fermions.
Conclusions:
- The large negative magnetoresistance in TaAs2 is not attributable to the Adler-Bell-Jackiw chiral anomaly of bulk Dirac/Weyl fermions.
- TaAs2 represents a new class of topological semimetals.
- The scattering mechanism responsible for NMR in TaAs2 remains to be identified, opening new research avenues.
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