Zeeman Field-Induced Two-Dimensional Weyl Semimetal Phase in Cadmium Arsenide

Binghao Guo, Wangqian Miao, Victor Huang, Alexander C. Lygo, Xi Dai, and Susanne Stemmer

Phys. Rev. Lett. 131, 046601 – Published 27 July 2023

Abstract

We report a topological phase transition in quantum-confined cadmium arsenide ( ${Cd}_{3} {As}_{2}$ ) thin films under an in-plane Zeeman field when the Fermi level is tuned into the topological gap via an electric field. Symmetry considerations in this case predict the appearance of a two-dimensional Weyl semimetal (2D WSM), with a pair of Weyl nodes of opposite chirality at charge neutrality that are protected by space-time inversion ( $C_{2} T$ ) symmetry. We show that the 2D WSM phase displays unique transport signatures, including saturated resistivities on the order of $h / e^{2}$ that persist over a range of in-plane magnetic fields. Moreover, applying a small out-of-plane magnetic field, while keeping the in-plane field within the stability range of the 2D WSM phase, gives rise to a well-developed odd integer quantum Hall effect, characteristic of degenerate, massive Weyl fermions. A minimal four-band $k \cdot p$ model of ${Cd}_{3} {As}_{2}$ , which incorporates first-principles effective $g$ factors, qualitatively explains our findings.

Received 6 May 2023
Revised 18 June 2023
Accepted 28 June 2023

DOI:https://doi.org/10.1103/PhysRevLett.131.046601

Physics Subject Headings (PhySH)

Quantum Hall effect

Topological materials Weyl semimetal

Condensed Matter, Materials & Applied Physics

Authors & Affiliations

Binghao Guo ¹, Wangqian Miao ¹, Victor Huang ¹, Alexander C. Lygo¹, Xi Dai ^1,2, and Susanne Stemmer ^1,*

¹Materials Department, University of California, Santa Barbara, California 93106-5050, USA
²Department of Physics, Hong Kong University of Science and Technology, Hong Kong, China

^*Corresponding author. stemmer@mrl.ucsb.edu

Article Text (Subscription Required)

Click to Expand

Supplemental Material (Subscription Required)

Click to Expand

References (Subscription Required)

Click to Expand

Issue

Vol. 131, Iss. 4 — 28 July 2023

Reuse & Permissions

Access Options

Article part of CHORUS

Accepted manuscript will be available starting 26 July 2024.

Author publication services for translation and copyediting assistance advertisement

Images

Figure 1
2D Weyl semimetal phase induced by a Zeeman field in confined ${Cd}_{3} {As}_{2}$ . (a) Dispersion of the semimetal phase with two Weyl nodes located at the Fermi level ( $E = 0 meV$ , dashed line). The 4 bands are spin resolved. For the $k \cdot p$ slab calculation, ${Cd}_{3} {As}_{2}$ has a thickness $d = 18 nm$ along [001] with an in-plane field $B_{ip} = 10 T$ . (b) Dispersion of the topological insulator phase with no external magnetic field. The spin-degenerate bands are drawn as dashed red lines. (b) Phase diagram of the $Γ$ -point energy gap in the $B_{ip} − d$ parameter space. The thickness range corresponds to the band inversion regime. Blue triangle, 2D WSM; red square, 2D TI.
Reuse & Permissions
Figure 2
Out-of-plane and in-plane magnetotransport. (a) Longitudinal conductivity $σ_{xx}$ as a function of the out-of-plane field $B_{oop}$ and the scaled (relative to $V_{CNP}$ ) top-gate voltage for the 18 nm sample (device, hb1). Quantum Hall plateau regions are indexed by their filling factor $ν$ up to 6. The measured voltage $V_{g}$ is offset by $V_{CNP}$ , which corresponds to the charge neutrality condition defined in the main text. (b) Longitudinal resistivity $ρ_{xx}$ as a function of the in-plane field $B_{ip}$ and the top-gate voltage for the 18 nm ${Cd}_{3} {As}_{2}$ sample (device, hb1). The same is shown in (c) for the 22 nm sample. $V_{CNP} = - 1.3 5 V$ for the 18 nm sample, $V_{CNP} = - 1.1 65 V$ for the 22 nm sample. Measurements were done at $T = 2 K$ in the transverse configuration.
Reuse & Permissions
Figure 3
Suppressed resistivity on the order of $h / e^{2}$ in the WSM phase. (a) Extracted $ρ_{xx}$ at the charge neutrality condition as a function of $B_{ip}$ for the 18 nm sample (devices hb1 and hb2 are on the same sample) and the 22 nm sample. (b) Close-up of the $B_{ip} > 9 T$ region for the data in (a). Shading indicates a $\pm 20 %$ interval around the resistance quantum $h / e^{2} \approx 2 5.8 1 k Ω$ (dashed line).
Reuse & Permissions
Figure 4
Odd integer quantum Hall effect and valley splitting. (a) Longitudinal and Hall conductivities, $σ_{xx}$ and $σ_{xy}$ , as a function top-gate voltage for a fixed $B_{oop} = 2.4 3 T$ . The same is shown in (b) for $B_{oop} = 3.6 2 T$ , in (c) for $B_{oop} = 4.7 9 T$ , and in (d) for $B_{oop} = 5.9 2 T$ . The total magnetic field $B_{tot} = 14 T$ , which is fixed, and $B_{ip} > 1 2.5 T$ in the four cases. $σ_{xy}$ is drawn with different colors and $σ_{xx}$ is drawn in black. Dashed black lines, $ν = odd$ integers. Bold lines, $ν = even$ integers, which are also labeled. The $σ_{xy} = 0$ plateaus are labeled separately.
Reuse & Permissions

Physical Review Letters