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Flat Optical Conductivity in ZrSiS due to Two-Dimensional Dirac Bands
M B Schilling1, L M Schoop2, B V Lotsch2
1Physikalisches Institut, Universität Stuttgart, Pfaffenwaldring 57, 70569 Stuttgart, Germany.
Physical Review Letters
|December 9, 2017
Summary
Zirconium silicon sulfide (ZrSiS) displays flat optical conductivity, similar to 2D Dirac materials like graphene. This unique property arises from Dirac bands and is influenced by nodal line length and spin-orbit coupling.
Area of Science:
- Condensed Matter Physics
- Materials Science
- Solid-State Physics
Background:
- Two-dimensional (2D) Dirac electron systems, such as graphene and graphite, exhibit unique electronic properties.
- Understanding the conductivity of novel materials is crucial for developing advanced electronic devices.
Purpose of the Study:
- To investigate the frequency-independent interband conductivity of ZrSiS.
- To compare the electronic properties of ZrSiS with known 2D Dirac systems.
- To determine the influence of spin-orbit coupling and nodal line length on ZrSiS conductivity.
Main Methods:
- Optical measurements were performed to determine the interband conductivity σ(ω).
- Analysis focused on the frequency range from 250 to 2500 cm⁻¹ (30–300 meV).
- The impact of spin-orbit coupling on Dirac bands was theoretically considered.
Main Results:
- ZrSiS exhibits a broad frequency-independent interband conductivity (σ_flat).
- This flat conductivity is attributed to transitions between quasi-2D Dirac bands near the Fermi level.
- Unlike graphene, σ_flat in ZrSiS depends on the nodal line length (k₀) and shows a small gap (Δ ≤ 30 meV) due to spin-orbit coupling.
Conclusions:
- ZrSiS behaves as a quasi-2D Dirac electron system with unique conductivity characteristics.
- The material's electronic properties are tunable via the nodal line length and influenced by spin-orbit coupling.
- At low temperatures (<50 K), momentum relaxation in ZrSiS occurs over micron-scale lengths.
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