Suppressed fluctuations as the origin of the static magnetic order in strained Sr$_2$RuO$_4$

TL;DR

This paper explains how uniaxial strain induces static magnetic order in Sr$_2$RuO$_4$ by suppressing quantum spin fluctuations more than magnetic tendencies, using density functional and renormalization theories.

Contribution

It combines first-principles calculations with Moriya's theory to elucidate the mechanism behind strain-induced magnetic order in Sr$_2$RuO$_4$.

Findings

Strain weakens quantum spin fluctuations more than magnetic stabilization.

A critical strain level triggers static magnetic order.

The rate of fluctuation suppression exceeds magnetic energy increase.

Abstract

Combining first principle density functional calculations and Moriya's self-consistent renormalization theory, we explain the recently reported counterintuitive appearance of an ordered magnetic state in uniaxially strained Sr$_2$RuO$_4$ beyond the Lifshits transition. We show that strain weakens the quantum spin fluctuations, which destroy the static order, more strongly than the tendency to magnetism. A different rate of decrease of the spin fluctuations vs. magnetic stabilization energy promotes the onset of a static magnetic order beyond a critical strain.