Direct observation of Landau level resonance and mass generation in Dirac semimetal Cd3As2 thin films

Abstract

Three-dimensional topological Dirac semimetals have hitherto stimulated unprecedented research interests as a new class of quantum materials. Breaking certain types of symmetries has been proposed to enable the manipulation of Dirac fermions; and that was soon realized by external modulations such as magnetic fields. However, an intrinsic manipulation of Dirac states, which is more efficient and desirable, remains a significant challenge. Here, we report a systematic study of quasi-particle dynamics and band evolution in Cd3As2 thin films with controlled Chromium (Cr) doping by both magneto-infrared spectroscopy and electrical transport. For the first time, we observe square-root-B relation of inter-Landau-level resonance in undoped Cd3As2 Dirac semimetal, an important signature of ultra-relativistic Dirac state inaccessible in previous optical experiments. A crossover from quantum to quasi-classical behavior makes it possible to directly probe the mass of Dirac fermions. Importantly, Cr doping allows for a Dirac mass acquisition and topological phase transition enabling a desired dynamic control of Dirac fermions. Corroborating with the density-functional theory calculations, we show that the mass generation is essentially driven by explicit C4 rotation symmetry breaking and the resultant Dirac gap engineering through Cr substitution for Cd atoms. The manipulation of the system symmetry and Dirac mass in Cd3As2 thin films provides a tuning knob to explore the exotic states stemming from the parent phase of Dirac semimetals.

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• A High-Performance Mid-infrared Optical Switch Enabled by Bulk Dirac Fermions in Cd3As2
• 3D Dirac semimetal Cd3As2: A review of material properties
• Chiral Landau levels in Weyl semimetal NbAs with multiple topological carriers
• Holographic quenches and anomalous transport
• Efficient generation of extreme terahertz harmonics in 3D Dirac semimetals
• Experimental Progress on Layered Topological Semimetals
• Electron Transport in Dirac and Weyl Semimetals
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• Strong electron-phonon coupling in 3D tungsten nitride and coexistence of intrinsic superconductivity and topological nodal line in its 2D limit