Measure the emergent-photon T^3 heat capacity and speed in quantum spin ice · revision history

Revision 2

Accepted · core change · record

Changes against revision 1:

Title
Measure the emergent-photon $T^3$ heat capacity and speed in quantum spin ice
Plain
Emergent photons should add a heat capacity growing as the cube of temperature, like lattice vibrations, with a size fixed by the photon speed. Measuring it and matching the speed predicted from the measured interactions would be a sharp test.
Precise · changed · core
Revision 1: In quantum spin ice the photon speed $c$ is set by the ring-exchange scale $g=12J_{\mathrm{pm}}^{3}/J_{\mathrm{zz}}^{2}$ (c ~ g $a$/hbar up to a computed prefactor, a the lattice spacing), and the photon heat capacity per volume is C/V = (4 pi^2/15) k_B (k_B T/hbar c)^3 for two polarizations. Measure $C/T^{3}$ below the photon bandwidth in a candidate material and compare $c$ with the value from independently fitted exchange parameters. An answer is $c$ measured and predicted, with agreement or disagreement within errors.
Revision 2: In quantum spin ice the photon speed $c$ is set by the ring-exchange scale $g=12J_{\mathrm{pm}}^{3}/J_{\mathrm{zz}}^{2}$ ($c \sim g$ $a$$/\hbar$ up to a computed prefactor, a the lattice spacing), and the photon heat capacity per volume is $C/V = (4 \pi^{2}/15) k_{\mathrm{B}} (k_{\mathrm{B}} T/\hbar c)^{3}$ for two polarizations. Measure $C/T^{3}$ below the photon bandwidth in a candidate material and compare $c$ with the value from independently fitted exchange parameters. An answer is $c$ measured and predicted, with agreement or disagreement within errors.
Settled by
Heat capacity below about 0.05 K with nuclear and phonon contributions subtracted, compared with the photon speed from neutron spectra and quantum Monte Carlo.
Kind
well-posed
Answer type
value
References
(empty)
Literature status
open
Status note
(empty)
Posed since
(empty)

Decisions