Does insulating $\mathrm{YbB_{12}}$ host a Fermi surface of neutral fermions?
This text mentions work from 2024 on. Those parts were partly written without a live literature search and have not been checked by an editor yet.
In plain words
$\mathrm{YbB_{12}}$ shows oscillations in resistance and magnetization, plus heat capacity and heat conduction that grow linearly with temperature as in a metal, while remaining electrically insulating.
Precise statement
In $\mathrm{YbB_{12}}$, quantum oscillations in resistivity and magnetization appear in the insulating state above $\sim 3.5 \times 10^{5}\,\mathrm{G}$ (Xiang et al. 2018), heat-capacity oscillations with frequency $\sim 6.7 \times 10^{6}\,\mathrm{G}$ were reported in 2025, and zero-field specific heat and thermal conductivity have linear-in-$T$ terms (Sato et al. 2019). Determine whether these signals come from a bulk Fermi surface of charge-neutral fermions.
What would settle it
Thermal transport and heat-capacity oscillations on crystals of varied purity, showing the fermion contribution is bulk and independent of metallic inclusions.
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.
Heat-capacity oscillations at a frequency matching torque and transport, with amplitude about 13 percent of the linear specific-heat coefficient, were reported in 2025 (Chen et al., Physical Review Letters 135, 156501, arXiv 2501.07471).
Parent problems
- Special case of Do Kondo insulators host charge-neutral fermions with a Fermi surface? · open · from revision 1 YbB12 is one of the Kondo insulators in the neutral-fermion question The parent was revised since revision 1: it now states another question.
- Special case of How can an insulator without a Fermi surface show quantum oscillations? · open · from revision 1 The parent was revised since revision 1: it now states another question.
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