Two-Terminal Electrical Detection of the Néel Vector via Longitudinal Antiferromagnetic Nonreciprocal Transport

Abstract

We propose a robust two-terminal electrical readout scheme for detecting the Néel vector orientation in antiferromagnetic (AFM) materials by leveraging longitudinal nonreciprocal transport driven by quantum metric dipoles. Unlike conventional readout mechanisms, our approach does not require spin-polarized electrodes, tunneling junctions, or multi-terminal geometries, offering a universal and scalable solution for AFM spintronics. As examples, we demonstrate pronounced second-order longitudinal nonlinear conductivity (LNC) in two-dimensional (2D) MnS and 3D CuMnAs, both of which exhibit clear sign reversal of LNC under 180$^\circ$ Néel vector reorientation. We show that this LNC is predominantly governed by the intrinsic, relaxation-time-independent quantum metric mechanism rather than the extrinsic nonlinear Drude effect. Our findings provide a practical and material-general pathway for electrically reading AFM memory states, with promising implications for next-generation AFM spintronic technologies.

Figures (4)

• Figure 1: Typical readout schemes for spintronics. (a) Tunneling magnetoresistance (TMR) in magnetic tunnel junction (MTJ) with two terminals for detecting the magnetic moment (i.e., state variable to encode the information). (b) Antiferromagnetic MTJ for detecting the Néel vector (i.e., state variable in antiferromagnets). (c) Hall measurement with four terminals for detecting the Néel vector. (d) Detection of the AFM Néel vector via longitudinal nonreciprocal transport without intricate junction structures or multi-terminal geometry.
• Figure 2: (a) The atomic structure of MnS $(\theta = 0)$ is depicted from both the side and top views, with Mn atoms possessing opposite magnetic moments represented in two distinct colors. (b) Band structure of MnS with $\theta = 0$ (orange) and $\theta=\pi$ (green). The Fermi level is set at the valence band maximum. The insert shows the BZ and the enlarged plot of the top two valence bands around the $\Gamma$ point. (c) Iso-energy surfaces at $\mu=-7$ meV for MnS with $\theta = 0$ and $\pi$, which exhibit opposite asymmetric distributions along the $k_y$ direction. (d) The quantum metric-induced LNC $\sigma_\mathrm{Mag}^{yyy}$ of MnS with $\theta = 0$ and $\pi$. (e) Distribution of $\lambda_n^{yyy}({\bm k})=v^y_nG_n^{yy}$ around $\Gamma$ for the top valence band of MnS with $\theta=0$. The orange line plots the iso-energy surfaces at $\mu=-7$ meV. (f) $\sigma_\mathrm{Mag}^{yyy}$ and $\sigma_\mathrm{Mag}^{xxx}$ of MnS at $\mu=-7$ meV when the Néel vector (denoted by $\theta$) rotates in the $x$-$y$ plane.
• Figure 3: The transverse and longitudinal nonlinear Drude conductivities $\sigma_\mathrm{Drude}^{yxx}$ and $\sigma_\mathrm{Drude}^{yyy}$ for MnS with $\theta=0$.
• Figure 4: (a) Atomic structure of tetragonal CuMnAs. (b) Quantum-metric induced LNC $\sigma_\mathrm{Mag}^{yyy}$ of CuMnAs with $\theta=0$. (c) The upper panel shows the band structure along the $\mathrm{Y^{\prime}-\Gamma-Y}$ line. The lower panel shows the distribution of $\sum_n[\frac{\partial f_n}{\partial \epsilon_n}\lambda_n^{yyy}({\bm k})]$ (color map) on the isoenergy surface of $\mu=22$ meV (orange lines) in the $k_x=0$ plane of the BZ. (d) $\sigma_\mathrm{Mag}^{yyy}$ and $\sigma_\mathrm{Mag}^{xxx}$ of CuMnAs at $\mu=22$ meV when the Néel vector (denoted by $\theta$) rotates in the $x$-$y$ plane.