High impact of spin-nematic order on the lattice domains in thin films of iron-based superconductors

TL;DR

This paper theoretically investigates how spin-nematic order influences lattice domain formation in thin films of iron-based superconductors, predicting a crossover thickness that could be experimentally observed to confirm spin nematicity.

Contribution

It introduces a Ginzburg-Landau model for spin-nematic effects in thin films and predicts a crossover in domain behavior related to film thickness, providing a new experimental probe.

Findings

Predicted a crossover thickness separating domain regimes

Derived analytical expressions for transition temperature and domain size

Proposed experimental observation of the crossover as evidence of spin nematicity

Abstract

The spin-nematic scenario proposed for the structural instability of iron-based superconductors is studied theoretically within a Ginzburg-Landau approach in epitaxial thin films. The transition temperature and the domains that appear due the interface with the substrate are computed analytically by following a variatonal procedure. It is predicted a cross-over thickness $l_*$ that separates the Kittel regime, in which the size of the domains goes as the square root of the film thickness $l$, from a new ultrathin regime in which the system tends to reach the single-domain state as $l \to 0$. The experimental observation of this cross-over is therefore proposed as a direct probe of spin nematiciy.