Magnetoresistance Scaling Reveals Symmetries of the Strongly Correlated Dynamics in ${\mathrm{BaFe}}_2({\mathrm{As}}_{1-x}{\mathrm{P}}_x{)}_2$

The phenomenon of $T$-linear resistivity commonly observed in a number of strange metals has been widely seen as evidence for the breakdown of the quasiparticle picture of metals. This study shows that a recently discovered $H/T$ scaling relationship in the magnetoresistance of the strange metal ${\mathrm{BaFe}}_2({\mathrm{As}}_{1-x}{\mathrm{P}}_x{)}_2$ is independent of the relative orientations of current and magnetic field. Rather, its magnitude and form depend only on the orientation of the magnetic field with respect to a single crystallographic axis: the direction perpendicular to the magnetic iron layers. This finding suggests that the magnetotransport scaling does not originate from the conventional averaging or orbital velocity of quasiparticles as they traverse a Fermi surface, but rather from dissipation arising from two-dimensional correlations.

Figure 1

Scaling in ${\rho }_c$ of ${\mathrm{BaFe}}_2({\mathrm{As}}_{1-x}{\mathrm{P}}_x{)}_2$. (a) The interlayer resistivity ${\rho }_c$ as a function of temperature. (Inset) A schematic phase diagram of ${\mathrm{BaFe}}_2({\mathrm{As}}_{1-x}{\mathrm{P}}_x{)}_2$, showing the AFM and superconducting transitions and the location of optimal doping (white circle). (b) Interlayer resistivity as a function of magnetic field up to 63 T at temperatures ranging from 4 to 36 K. The $H$-linear MR is apparent at low temperatures where $\rho$ is roughly independent of $T$. (c) A scaling plot of the MR curves shown in (b). The residual resistivity (found by fitting the 4 K curve to a line and taking the $H=0$ intercept) is subtracted off and the remainder is normalized to the temperature and plotted versus $H/T$.

Figure 2

MR of ${\mathrm{BaFe}}_2({\mathrm{As}}_{1-x}{\mathrm{P}}_x{)}_2$ in ${\rho }_{ab}$ and ${\rho }_c$ with $H$ in the plane. (a) MR of ${\rho }_{ab}$ as a function of transverse (in-plane) magnetic field up to 63 T at temperatures ranging from 4 to 36 K. Although $H_{C2}$ is very close to 60 T, we can see that there is still strong temperature dependence at high fields, and thus $H\text{−}T$ scaling of the form found with field along the $c$ axis is not present. (b) The same plot but for ${\rho }_c$. (c) Fractional MR of ${\rho }_{ab}$ in the longitudinal configuration. Below about 100 K the MR becomes negative and has a similar magnitude to the transverse in-plane configuration. Diagrams on the right are schematic representations of each experimental configuration.

Figure 3

Transverse MR of ${\rho }_{ab}$ and with $H$ rotated away from the $c$ axis. (a) Raw MR at 10 K as a function of $H$ for several orientations of the magnetic field. The field was always maintained perpendicular to the current but rotated away from the $c$ axis by the amount shown. (b) The same curves plotted in panel (A), but this time as a function of the combined field-temperature energy scale, ${\mathrm{\Gamma }}_c$, using only the component of the field along the $c$ axis.