Intrinsic versus defect-driven phonon thermal Hall effect in $\mathrm{SrTiO_3}$
In plain words
The effect could come from the phonons themselves or from the way they scatter off impurities. $\mathrm{SrTiO_3}$, where it is large, is a clean place to decide.
Precise statement
For $\mathrm{SrTiO_3}$ with $\kappa_{xy}/\kappa_{xx}$ up to $\sim 3 \times 10^{-3}$ at $9 \times 10^{4}\,\mathrm{G}$ near the $\kappa_{xx}$ maximum, determine whether $\kappa_{xy}$ arises from band-intrinsic phonon chirality (for example involving the soft polar mode and structural domains) or from extrinsic skew scattering, by establishing how $\kappa_{xy}$ scales with $\kappa_{xx}$ and with controlled defect density (oxygen vacancies, isotope substitution).
What would settle it
$\kappa_{xy}$ measured on crystals with independently quantified defect density, combined with first-principles phonon Berry curvature for $\mathrm{SrTiO_3}$.
Status in the literature
Unverified note: it names recent work and was partly written without a live literature search; it awaits a check by an editor.
In $\mathrm{SrTiO_3}$ disorder and strain suppress $\kappa_{xy}$ and annealing partly restores it without changing $\kappa_{xx}$ (Xiang et al., npj Quantum Materials 11, 40, 2026, arXiv 2511.08932); the authors read this as an intrinsic lattice effect sensitive to imperfections, not yet tied to a microscopic mechanism.
Parent problems
- Special case of Why do phonons in many insulators show a thermal Hall effect? · open · from revision 1 The parent was revised since revision 1: it now states another question.
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