High-resolution angle-resolved photoemission study of large magnetoresistance topological semimetal CaAl4 *

Extremely large magnetoresistance (XMR) has been explored in many nonmagnetic topologically nontrivial/trivial semimetals, while it is experimentally ambiguous which mechanism should be responsible in a specific material due to the complex electronic structures. In this paper, the magnetoresistance origin of single crystal CaAl4 with C2/m structure at low temperature is investigated, exhibiting unsaturated magnetoresistance of similar to 3000% at 2.5 K and 14 T as the fingerprints of XMR materials. By the combination of ARPES and the first-principles calculations, we elaborate multiband features and anisotropic Fermi surfaces, which can explain the mismatch of isotropic two-band model. Although the structural phase transition from I4/mmm to C2/m has been recognized, the subtle impact on electronic structure is revealed by our ARPES measurements. Considering that both charge compensation and potential topologically nontrivial band structure exist in CaAl4, our findings report CaAl4 as a new reference material for exploring the XMR phenomena.

Automated summary

This paper investigates the magnetoresistance origin of single crystal CaAl4 with C2/m structure at low temperature, revealing unsaturated magnetoresistance of around 3000% at 2.5 K and 14 T as the fingerprints of XMR materials. The study uses a combination of ARPES and first-principles calculations to elaborate on the multiband features and anisotropic Fermi surfaces, explaining the discrepancies in the isotropic two-band model. Despite a structural phase transition from I4/mmm to C2/m, the subtle impact on the electronic structure is revealed through ARPES measurements, highlighting CaAl4 as a new reference material for exploring the XMR phenomena.