Do Kondo insulators host charge-neutral fermions with a Fermi surface? · revision history

Revision 2

Accepted · core change · record

Changes against revision 1:

Title · changed
Revision 1: Do Kondo insulators host charge-neutral fermions with a Fermi surface
Revision 2: Do Kondo insulators host charge-neutral fermions with a Fermi surface?
Plain · changed
Revision 1: Some insulators built from heavy-fermion elements, such as YbB12 and SmB6, show metal-like signatures, heat conduction by mobile carriers and quantum oscillations, while not conducting electricity; this would require particles that carry heat but no charge.
Revision 2: Some insulators built from heavy-fermion elements, such as $\mathrm{YbB_{12}}$ and $\mathrm{SmB_6}$, show metal-like signatures, heat conduction by mobile carriers and quantum oscillations, while not conducting electricity; this would require particles that carry heat but no charge.
Precise · changed · core
Revision 1: Determine whether a finite residual thermal conductivity $\kappa_{xx}/T$ at $T \to 0$ and bulk quantum oscillations in insulating Kondo insulators (YbB12, SmB6) arise from charge-neutral fermions with a Fermi surface (Majorana or composite-exciton Fermi seas) or from phonons, magnetic impurities and metallic inclusions. An answer is field-dependent $\kappa_{xx}/T$ and specific heat $\gamma$ on crystals with controlled impurity content, compared with a theory that predicts their magnitudes.
Revision 2: Determine whether a finite residual thermal conductivity $\kappa_{xx}/T$ at $T \to 0$ and bulk quantum oscillations in insulating Kondo insulators ($\mathrm{YbB_{12}}$, $\mathrm{SmB_6}$) arise from charge-neutral fermions with a Fermi surface (Majorana or composite-exciton Fermi seas) or from phonons, magnetic impurities and metallic inclusions. An answer is field-dependent $\kappa_{xx}/T$ and specific heat $\gamma$ on crystals with controlled impurity content, compared with a theory that predicts their magnitudes.
Settled by
Thermal conductivity and specific heat at millikelvin temperatures on sets of crystals with independently measured impurity and inclusion densities, showing whether the residual terms survive as extrinsic content goes to zero.
Kind
well-posed
Answer type
yes-no
References
(empty)
Literature status
contested
Status note · changed
Revision 1: Sato et al. (Nature Physics 2019) reported finite $\kappa/T$ at $T \to 0$ in YbB12; for SmB6, Hartstein et al. (2018) attributed field-dependent heat transport to neutral fermions and Boulanger et al. (2018) to phonons scattered by magnetic impurities.
Revision 2: Sato et al. (Nature Physics 2019) reported finite $\kappa/T$ at $T \to 0$ in $\mathrm{YbB_{12}}$; for $\mathrm{SmB_6}$, Hartstein et al. (2018) attributed field-dependent heat transport to neutral fermions and Boulanger et al. (2018) to phonons scattered by magnetic impurities.
Posed since
2015

Decisions