Fragile unconventional magnetism in <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msub> <mml:mi>RuO</mml:mi> <mml:mn>2</mml:mn> </mml:msub> </mml:math> by proximity to Landau-Pomeranchuk instability
Zhuang Qian, Yudi Yang, Shi Liu, Congjun Wu
Abstract
Altermagnetism has attracted considerable attention for its remarkable combination of spin-polarized band structures and zero net magnetization, making it a promising candidate for spintronics applications. We demonstrate that this magnetic phase represents a case of unconventional magnetism, first proposed nearly two decades ago by one of the present authors as part of a broader framework for understanding Landau-Pomeranchuk instabilities in the spin channel, driven by many-body interactions. By systematically analyzing the altermagnetism in ${\mathrm{RuO}}_{2}$ with first-principles calculations, we reconcile conflicting experimental and theoretical reports by attributing it to ${\mathrm{RuO}}_{2}$'s proximity to a quantum phase transition. We emphasize the critical role of tuning parameters, such as the Hubbard $U$, hole doping, and epitaxial strain, in modulating quasiparticle interactions near the Fermi surface. This work provides fresh insights into the origin and tunability of altermagnetism in ${\mathrm{RuO}}_{2}$, highlighting its potential as a platform for investigating quantum phase transitions and the broader realm of unconventional magnetism.