Revision 1

Superseded · first revision · record

Title: Does the Fermi volume of YbRh2Si2 jump at its critical field
Plain: Hall-effect data suggest that the number of electrons in the Fermi sea of YbRh2Si2 changes abruptly at a critical magnetic field when cooled to zero temperature.
Precise: In YbRh2Si2 at $T \to 0$ across the critical field $B_c \sim 600\,\mathrm{G}$ (field in the ab plane), determine whether the Fermi volume changes discontinuously from large (including the 4f hole) to small, as inferred from the Hall crossover whose width scales with $T$. An answer is a $T = 0$ extrapolation of the crossover width of Fermi-volume-sensitive transport (Hall coefficient, thermopower) in crystals with residual resistivity ratio of order 100 or more, or a Fermi-surface measurement at fields close to $B_c$, for example on chemically substituted samples whose critical field lies in the range accessible to quantum oscillations.
Settled by: Hall and thermopower crossover widths measured below 10 mK on the cleanest crystals and extrapolated to $T = 0$, together with Fermi-surface data on substituted samples whose critical field is high enough for quantum oscillations.
Kind: well-posed
Answer type: yes-no
References: (empty)
Literature status: contested
Status note: ARPES (2015) found a large Fermi surface at zero field down to about 1 K, well above the crossover temperatures; no direct Fermi-surface measurement at $B_{\mathrm{c}}$ exists.
Posed since: 2004