CM In the literature: contested

Is the half-quantized thermal Hall plateau in $\alpha$-RuCl3 reproducible?

In plain words

One group reported that the sideways heat flow stops changing with field at exactly half of a fundamental quantum value, the signature of a single Majorana edge channel. Other groups saw values near it without a flat plateau, or a strongly temperature-dependent signal, so it is unclear whether it is a real property of the material.

Precise statement

Test whether $\kappa_{xy}/T = (1/2)(\pi^2 k_B^2/3h)$ holds within 10 percent over a finite field range in $\alpha$-RuCl3 in the field-induced disordered regime (in-plane $H$ near 70 to 90 kOe, $T$ about 4 to 6 K), and whether it is independent of sample width and of $\kappa_{xx}$ as an edge mode requires. An answer is yes with reproducible data from independent groups, or a demonstration that the apparent plateau is an accidental crossing of a nonquantized phonon or magnon signal.

What would settle it

Independent measurements on multiple samples of different widths and $\kappa_{xx}$ values, including constrictions, showing the plateau value and its size independence, or its absence.

Status in the literature

Reported by Kasahara et al. (Nature 2018) and Yokoi et al. (Science 2021); Bruin et al. (Nature Physics 2022) found $\kappa_{xy}/T$ near the half-quantized value over an extended region but without a strict plateau; Czajka et al. (Nature Materials 2023) found a strongly $T$-dependent kappa_xy/T and attributed it to topological magnons.