Néel vector controlled charge and spin transport in altermagnetic junctions

TL;DR

This work develops a theoretical framework for charge and spin transport in altermagnetic junctions, distinguishing strong and weak altermagnetic phases by the parameter $t_J/t$. Using a continuum model and Landauer-style scattering, it shows that in the weak phase the conductance depends smoothly on the Néel-vector angle $\theta$ and can remain finite at $\theta=\pi$, while in the strong phase transport is dominated by a single spin channel and vanishes at $\theta=\pi$ due to momentum mismatch. Introducing a normal-metal spacer between AMs yields Fabry-Pérot–type oscillations in the conductance, tunable by spacer length $L$ and gate voltage $\mu$, with oscillation characteristics differing between phases. Collectively, the results indicate AM-based heterostructures as versatile platforms for spin filtering and interference-based spintronic devices, with clear experimental pathways via Néel vector control.

Abstract

We theoretically investigate electron transport in junctions between the two altermagnets (AMs) in strong and weak altermagnetic phases. The charge and spin conductivities are analyzed as functions of angle $θ$ between the Néel vectors of the two AMs. In the strong AM regime, the charge conductivity vanishes as $θ\to π$, while in the weak AM regime it remains finite. Introducing a normal metal between two AMs leads to Fabry-Pérot-type oscillations in charge conductivity which can be controlled by an applied gate voltage. In the strong regime, transport is dominated by up-spin electrons, whereas both spin channels contribute in the weak regime. These results highlight the potential of AM-based heterostructures for spintronic applications, such as spin filters, and quantum interference-based spintronic devices, where tunable spin-dependent transport and interference effects can be utilized in electronic devices.

Figures (4)

• Figure 1: (a) Schematic of the junction with the Fermi surfaces on each region. The Néel vectors on either sides of the junction differ by an angle $\theta$. (b) Differential charge conductivity versus $\theta$ for different values of $t_J/t$ indicated in the legend. Other parameters: $q_0=1/a$, $c=1$, $E=t$ (c) Spin conductivity versus $\theta$ in the left and right AM for $q_0=0$, $c=1.2$, $t_J=0.2$ and $E=t$.
• Figure 2: (a) Schematic of the system. Fermi surfaces in each region are indicated by curves. The Néel vectors on the left AM and right AM differ by an angle $\theta$. Differential conductivity (b) versus $L$ in the units of $a$ keeping $\mu=t_0$, (c) versus $\mu$ in the units of $t_0$ keeping $L=20$ for two different values of $\theta$ i.e $\theta=0~{\rm and}~~\pi$ indicated in the legend. Other parameters: $q_0=1/a$, $c=1$, $t_J=0.2t$, $E=t$ are same for (b) and (c)
• Figure 3: (a) Schematic of the system. The curves indicate Fermi surface. The Néel vectors on the left AM and right AM differ by an angle $\theta$. (b) Differential charge conductivity versus $\theta$ and (c) spin conductivity versus $\theta$ for different values of $t_J$ as indicated in the legend. Other parameters: $q_0=1/a$, $c=1$, $E=t_J$ (d) Fermi surface of up- and down-spin electrons for different values of $t$.
• Figure 4: (a) Schematic of the system. The curves show Fermi surfaces in each region. The Néel vectors on the left AM and right AM differ by an angle $\theta$. Total charge conductivity (b) versus $\theta$ keeping $L=3a$ and $\mu=t_J$ (c) versus $\mu$ keeping $L=4a$ and $\theta=0$, and (d) versus $L$ keeping $\mu=2t_J$ and $\theta=0$ for $\uparrow$ and $\downarrow$ spin electrons indicated in the legend. Other parameters: $q_0=1/a$, $c=1$, $t=0.1t_J$, $E=t_J$.