Dirac semimetal in β-CuI without surface Fermi arcs.

Area of Science:

• Condensed matter physics
• Materials science
• Solid-state physics

Background:

• Anomalous surface states with Fermi arcs are considered a hallmark of Dirac semimetals (DSMs).
• Unlike Weyl semimetals, Fermi arcs in DSMs lack topological protection.
• Understanding the behavior of surface states in DSMs is crucial for exploring novel electronic properties.

Purpose of the Study:

• To investigate the nature of surface states in β-cuprous iodide (β-CuI) using first-principles calculations.
• To identify the underlying mechanisms responsible for the observed surface state characteristics in β-CuI.
• To establish β-CuI as a material example that demonstrates the non-topological nature of DSM surface Fermi arcs.

Main Methods:

• First-principles calculations were employed to study the electronic structure of β-cuprous iodide.
• Analysis focused on the surface states and their topological properties.
• Comparison of calculated surface states with theoretical predictions for Dirac semimetals.

Main Results:

• β-cuprous iodide (β-CuI) was predicted to be a Dirac semimetal (DSM) with unusual surface states.
• Instead of Fermi arcs, the surface states of β-CuI form closed Fermi pockets.
• This deformation is attributed to a significant cubic term and small energy differences between surface and bulk Dirac points.

Conclusions:

• β-cuprous iodide (β-CuI) serves as a concrete material example of a fermiological Dirac semimetal.
• The study highlights that Fermi arcs in DSMs are not always topologically protected.
• The findings underscore the importance of crystal structure and specific electronic parameters in determining surface state topology.