Elemental Topological Dirac Semimetal: α-Sn on InSb(111)

Area of Science:

• Condensed matter physics
• Materials science
• Topological materials

Background:

• Three-dimensional (3D) topological Dirac semimetals (TDSs) are rare materials hosting unique electronic properties.
• These materials are crucial for studying exotic electronic behaviors and topological phase transitions.
• A key characteristic of TDSs is the presence of 3D Dirac fermions near the Fermi level.

Purpose of the Study:

• To realize and characterize a new 3D topological Dirac semimetal system.
• To investigate the role of epitaxial strain in forming the TDS phase.
• To establish a phase diagram connecting TDS, zero-gap semimetal, and topological insulator phases.

Main Methods:

• Angle-resolved photoemission spectroscopy (ARPES) to observe bulk Dirac cones.
• Epitaxial growth of alpha-tin (α-Sn) films on indium antimonide (InSb(111)) substrates.
• First-principles calculations to understand the electronic structure and phase formation.

Main Results:

• Observation of bulk Dirac cones in epitaxially grown α-Sn films on InSb(111).
• Confirmation that epitaxial strain is essential for the formation of the 3D TDS phase.
• Establishment of a phase diagram showing the transition between 3D TDS, zero-gap semimetal, and topological insulator phases.
• Demonstration of the crossover of Dirac cone nature from 3D to 2D with decreasing film thickness.

Conclusions:

• Epitaxially grown α-Sn films on InSb(111) represent the first elemental realization of a 3D topological Dirac semimetal.
• Epitaxial strain is a critical factor in stabilizing the TDS phase.
• The film thickness dictates the dimensionality of the observed Dirac cones, offering tunability.