Negative Differential Resistance and Ultra-High TMR in Altermagnetic Tunnel Junctions

TL;DR

This paper predicts that altermagnetic tunnel junctions exhibit large negative differential resistance and high tunneling magnetoresistance at low bias, enabled by their unique electronic structure, with potential applications in non-linear electronic devices.

Contribution

It introduces the first prediction of negative differential resistance in altermagnetic tunnel junctions using non-equilibrium Green's functions and density functional theory.

Findings

Large low-bias negative differential resistance observed around 0.14 V.

Tunneling magnetoresistance with sign inversion at 0.13 V.

The orbital-ordered KV2Se2O plays a key role in the non-linear behaviour.

Abstract

Altermagnets can replace ferromagnets in tunnel junctions, yielding large tunneling magnetoresistance, ultrafast switching, and low-power functionality. While most studies explore the linear-response regime, interesting features emerge at finite bias, where the peculiar electronic structure of altermagnets gives rise to complex non-linear behaviour. Using non-equilibrium Green's functions implemented with density functional theory, we predict that a large low-bias negative differential resistance can be observed in an altermagnetic tunnel junction. Our proposed junction incorporates the orbital-ordered altermagnet KV2Se2O, whose quasi-2D Fermi surface plays a crucial role in realizing the negative differential resistance. Upon the application of a finite bias voltage, the current in the parallel configuration first increases sharply and then decreases, to be almost completely suppressed at around 0.14 V. At the same time, the antiparallel configuration displays a monotonic current-voltage curve. This behaviour, in addition to the negative differential resistance, supports a large tunneling magnetoresistance with sign inversion at 0.13 V. Our results suggest that altermagnetic tunnel junctions can be used as components in applications requiring strong non-linear response at low bias.