Dirac Nodal Line in Hourglass Semimetal Nb₃SiTe₆

Area of Science:

• Condensed Matter Physics
• Materials Science
• Topological Materials

Background:

• Nonsymmorphic crystals with glide-mirror symmetry can host exotic electronic states.
• Hourglass nodal loop states are predicted topological phases with unique electronic properties.

Purpose of the Study:

• To spectroscopically investigate the predicted topological hourglass semimetal phase in Nb3SiTe6.
• To identify and characterize the electronic band structure responsible for novel quantum phenomena.

Main Methods:

• Angle-resolved photoemission spectroscopy (ARPES) was used to probe the electronic band structure.
• In situ alkali-metal doping was employed to tune the electronic properties and observe additional band crossings.

Main Results:

• Linear band crossings were observed at the zone boundary, consistent with a glide quantum spin Hall effect and forming a nodal loop.
• A saddle-like Fermi surface was identified, revealing previously unobserved linear band crossings.
• Doping studies showed additional band crossings and parabolic bands at the zone center, linked to accidental nodal loop states.

Conclusions:

• The study confirms the existence of a topological hourglass semimetal phase in Nb3SiTe6.
• The observed band structure explains prior Hall measurements and supports the presence of a nodal loop.
• Nb3SiTe6 serves as a promising platform for exploring glide quantum spin Hall effects and topological phenomena.