Quantum transport evidence for a three-dimensional Dirac semimetal phase in Cd3As2 (1404.2557v3)

Abstract: The material termed three-dimensional (3D) Dirac semimetal has attracted great interests recently, since it is an electronic analogue to two-dimensional graphene. Starting from this novel phase, various topologically distinct phases may be obtained, such as topological insulator, Weyl semimetal, quantum spin Hall insulator, and topological superconductor. Soon after the theoretical predictions, the angle-resolve photoemission spectroscopy and scanning tunnelling microscopy experiments gave evidences for 3D Dirac points in Na3Bi and Cd3As2. Here we report quantum transport properties of Cd3As2 single crystal in magnetic field. A sizable linear quantum magnetoresistance is observed at high temperature. With decreasing temperature, the Shubnikov-de Haas oscillations appear in both longitudinal resistance Rxx and transverse Hall resistance Rxy. From the strong oscillatory component \Delta Rxx, the linear dependence of Landau index n on 1/B gives an n-axis intercept 0.58. Our quantum transport result clearly reveals a nontrivial \pi\ Berry's phase, thus provides strong bulk evidence for a 3D Dirac semimetal phase in Cd3As2. This may open new perspectives for its use in electronic devices.

• The paper demonstrates linear magnetoresistance reaching 200% at 14.5 T, confirming Dirac fermion behavior in Cd3As2.
• The study uses Shubnikov–de Haas oscillations to reveal a π Berry’s phase and high carrier mobility (4.1×10⁴ cm²/Vs) at 1.5 K.
• The findings underscore Cd3As2's potential in advanced electronic applications and encourage further exploration of Dirac semimetal physics.

Quantum Transport Evidence for a Three-Dimensional Dirac Semimetal Phase in Cd$_3$As$_2$

The paper presents significant insights into the quantum transport properties of Cd$_3$As$_2$, a three-dimensional (3D) Dirac semimetal. This paper is positioned in the context of the emerging interest in 3D Dirac semimetals, which serve as electronic analogues to the well-studied two-dimensional graphene and are capable of leading to various topologically distinct phases, such as Weyl semimetals and topological insulators.

The investigation undertakes quantum transport measurements on Cd$_3$As$_2$ single crystals in a magnetic field. One of the key observations is the linear quantum magnetoresistance (MR) at room temperature—a prominent characteristic predicted for Dirac fermions with linear energy dispersion, even though the quantum limit is not actualized. A detailed analysis using Shubnikov-de Haas (SdH) oscillations substantiates the emergence of a nontrivial π Berry’s phase, pivotal in evidencing the existence of a 3D Dirac semimetal phase.

Key Observations and Numerical Results

The paper outlines the following quantitative results:

1. Linear Quantum Magnetoresistance: The MR displayed a rough linearity with no saturation, extending as high as 200% at 14.5 T, a unique phenomenon in comparison to typical conductors.
2. Shubnikov-de Haas Oscillations: The detection of SdH oscillations in both longitudinal and transverse Hall resistances supports high carrier mobility intrinsic to 3D Dirac semimetals. Specifically, carrier mobility is evaluated at 4.1 × 10$^4$ cm$^2$/Vs at 1.5 K.
3. Landau Index Analysis: The analysis reveals an n-axis intercept of 0.58 in the Landau index plot, confirming a π Berry’s phase, which contrasts the trivial 0 phase expected in conventional metals. This nontrivial phase is crucial for validating the presence of Dirac fermions in the compound.
4. Fermi Surface Characteristics: Through FFT analysis, a single oscillation frequency $F = 58.3$ T was identified, leading to the calculation of a small Fermi momentum $k_F$ of approximately 0.042 Å$^-1$.

Implications and Future Directions

The findings in this paper are substantial for both theoretical and practical realms. The confirmation of a 3D Dirac semimetal phase in Cd$_3$As$_2$ not only complements previous ARPES and STM studies but also highlights the potential for this material in electronic applications. The high room-temperature linear MR and the nontrivial π Berry’s phase could pave the way for innovations in electronic devices, particularly in magnetic memory and sensor technologies.

The work suggests a promising avenue for future exploration into the conductivity properties of Dirac semimetals under varying conditions, such as different doping levels or dimensional configurations. These modifications may substantially enhance the magnitude of MR, thereby increasing the applicability in technological domains. Additionally, further theoretical investigations are warranted to elucidate the peculiar linear MR observed and its dependency on three-dimensional crystal structures.

In summary, the reported evidence advances the understanding of 3D Dirac semimetals, with Cd$_3$As$_2$ at the forefront, reinforcing its potential to contribute significantly to the field of condensed matter physics and beyond.