Lorentz-Boost-Driven Magneto-Optics in a Dirac Nodal-Line Semimetal

Area of Science:

• Condensed Matter Physics
• Materials Science
• Quantum Mechanics

Background:

• Optical and magneto-optical methods are standard for determining the energy band gap in crystalline solids.
• The energy band gap is a fundamental property essential for understanding solid materials.
• Topological Dirac semimetals possess unique electronic structures with nodal lines.

Purpose of the Study:

• To investigate the applicability of conventional optical methods to topological Dirac semimetals.
• To understand the unusual optical response observed in these materials.
• To explain the dependence of the deduced band gap on magnetic field orientation.

Main Methods:

• Application of optical and magneto-optical techniques to topological Dirac semimetals.
• Analysis of electron band excitations and their relation to optical properties.
• Theoretical explanation based on the Dirac Hamiltonian and Lorentz covariance.

Main Results:

• Conventional methods for band gap determination were found to be ineffective in topological Dirac semimetals with nodal lines.
• The optically deduced band gap showed a dependence on the orientation of the applied magnetic field relative to crystal axes.
• This anisotropic behavior was attributed to band-gap renormalization effects.

Conclusions:

• Standard optical techniques require re-evaluation for materials exhibiting topological nodal line semimetal properties.
• The observed anisotropy in the band gap is a consequence of Lorentz boosts acting on the low-energy Dirac Hamiltonian.
• Understanding this phenomenon is crucial for accurately characterizing the electronic properties of topological semimetals.