Observation of a topological 3D Dirac semimetal phase in high-mobility Cd3As2 (1309.7892v4)

Abstract: Experimental identification of three-dimensional (3D) Dirac semimetals in solid state systems is critical for realizing exotic topological phenomena and quantum transport such as the Weyl phases, high temperature linear quantum magnetoresistance and topological magnetic phases. Using high resolution angle-resolved photoemission spectroscopy, we performed systematic electronic structure studies on well-known compound Cd3As2. For the first time, we observe a highly linear bulk Dirac cone located at the Brillouin zone center projected onto the (001) surface which is consistent with a 3D Dirac semimetal phase in Cd3As2. Remarkably, an unusually high Dirac Fermion velocity up to 10.2 \textrm{\AA}{\cdot}$eV (1.5 \times 10^{6} ms^-1) is seen in samples where the mobility far exceeds 40,000 cm^2/V.s suggesting that Cd3As2 can be a promising candidate as a hypercone analog of graphene in many device-applications which can also incorporate topological quantum phenomena in a large gap setting. Our experimental identification of this novel topological 3D Dirac semimetal phase, distinct from a 3D topological insulator phase discovered previously, paves the way for exploring higher dimensional relativistic physics in bulk transport and for realizing novel Fermionic matter such as a Fermi arc nodal metal.

• The paper demonstrates a three-dimensional Dirac semimetal phase in Cd3As2 with a linear energy-momentum dispersion and symmetry-protected Dirac points.
• The study employs high-resolution ARPES and theoretical calculations to identify a Dirac point at 0.2 eV with Fermi velocities reaching 1.5 million m/s and mobility up to 40,000 cm²V⁻¹s⁻¹.
• The paper highlights Cd3As2’s potential for quantum computing and spintronics through its robust topological properties and capability to evolve into Weyl semimetal phases under perturbations.

Discovery of a Three-Dimensional Topological Dirac Semimetal Phase in High-Mobility Cd$_3$As$_2$

This paper presents a comprehensive investigation into the electronic structure of Cd$_3$As$_2$, a compound identified as a three-dimensional topological Dirac semimetal (BDS) with high electron mobility. Through meticulous experimentation using angle-resolved photoemission spectroscopy (ARPES), the paper reveals pivotal characteristics that position Cd$_3$As$_2$ as a promising candidate for exploring novel topological phases in condensed matter physics. The focus of this paper lies in the realization and characterization of a Dirac-like fermionic system with unique dispersive properties and significant potential for future applications in quantum computing and material science.

Numerical Observations and Results

In their experiments, the researchers employed high-resolution ARPES to observe the existence of a Dirac-like band crossing in the bulk state of Cd$_3$As$_2$. The compound was found to exhibit remarkably high Fermi velocities, reaching approximately 1.5 million meters per second in the plane, along with impressive electronic mobility of up to 40,000 cm$^2$V$^{-1}$s$^{-1}$. These metrics are indicative of the compound's potential for supporting exotic quantum transport properties, similar to those observed in two-dimensional graphene systems.

Experimental Approach and Findings

The authors successfully demonstrate a massless, three-dimensional Dirac dispersion characterized by linear energy-momentum behavior in three orthogonal directions. This finding is vital as it differs from two-dimensional Dirac systems, such as those in graphene and topological insulators, due to the lack of full energy gaps in such three-dimensional systems. The experimental setup identified a Dirac point at a binding energy of approximately 0.2 eV, with symmetry protection attributed to the $C_4$ rotational crystalline symmetry.

Theoretical and Experimental Implications

The theoretical predictions align closely with the empirical observations, offering a consistent explanation of the band structure derived from first-principles calculations. The identification of Cd$_3$As$_2$ as a high mobility single-crystal Dirac semimetal presents a distinct opportunity to elucidate three-dimensional topological quantum phenomena. Given its stoichiometric nature, Cd$_3$As$_2$ avoids issues such as disorder and variability inherent in alloyed systems. The combination of strong spin-orbit coupling and crystal symmetry enables a robust Dirac state, opening avenues for realizing Weyl semimetal phases, quantum spin Hall effects, and other topological manifestations upon further investigation.

Future Prospects and Conclusion

This research has pivotal implications for future studies aiming to harness the unique properties of three-dimensional Dirac semimetals. The high mobility and spin-orbit interactions propose Cd$_3$As$_2$ as an exemplary system for experimental exploration of high-temperature quantum transport and spintronics applications. Additionally, the ability to transform the Dirac state into other topologically nontrivial states by perturbing crystal symmetry (e.g., via magnetic doping) or under conditions such as high magnetic fields indicates a broad spectrum of future research directions.

In conclusion, the discovery and substantiation of a three-dimensional topological Dirac semimetal phase in Cd$_3$As$_2$ not only contribute significantly to fundamental understanding in condensed matter physics but also pave the way towards revolutionary advancements in material science and quantum computing technology. The well-defined Dirac cone and highly mobile carriers underscore the potential of Cd$_3$As$_2$ for innovative physical research and technological applications in the field of quantum devices.