Are the surface Fermi arcs in Dirac semimetals topologically protected?

Area of Science:

• Condensed Matter Physics
• Materials Science
• Topological Materials

Background:

• Recent experiments explore anomalous surface states in Dirac semimetals (DSMs) like Na3Bi and Cd3As2.
• Understanding the topological protection of these surface states is crucial for their applications.

Purpose of the Study:

• To investigate the topological protection of gapless surface states in Dirac semimetals.
• To contrast the surface state properties of DSMs with those of Weyl semimetals.

Main Methods:

• Utilized a minimal four-band model with Dirac nodes.
• Performed K-theory analysis for the space groups of Na3Bi and Cd3As2.
• Investigated surface Brillouin zone properties.

Main Results:

• Gapless surface states in DSMs are not generally topologically protected, except on specific time-reversal-invariant planes.
• Surface states are protected near specific points in the surface Brillouin zone.
• Fermi arcs in DSMs generically deform into Fermi pockets, merging with bulk Dirac Fermi surface projections.

Conclusions:

• The topological protection of DSM surface states differs significantly from Weyl semimetals.
• Surface states exhibit doping-dependent behavior that can be experimentally verified.
• Findings provide insights into the fundamental properties of topological materials.