Extremely Large Magnetoresistance in the Nonmagnetic Metal ${\mathrm{PdCoO}}_2$

Extremely large magnetoresistance is realized in the nonmagnetic layered metal ${\mathrm{PdCoO}}_2$. In spite of a highly conducting metallic behavior with a simple quasi-two-dimensional hexagonal Fermi surface, the interlayer resistance reaches up to 35 000% for the field along the $[1\overline{1}0]$ direction. Furthermore, the temperature dependence of the resistance becomes nonmetallic for this field direction, while it remains metallic for fields along the [110] direction. Such severe and anisotropic destruction of the interlayer coherence by a magnetic field on a simple Fermi surface is ascribable to orbital motion of carriers on the Fermi surface driven by the Lorentz force, but seems to have been largely overlooked until now.

Figure 1

Temperature dependence of the interlayer resistivity ${\rho }_c$ for several magnetic fields along the (a) $[1\overline{1}0]$ and (b) [110] directions. The strong enhancement with a nonmetallic upturn was observed for $H\parallel [1\overline{1}0]$. In contrast, the enhancement for $H\parallel [110]$ is an order of magnitude smaller. The left-hand inset of (b) is a schematic drawing of the FS with its relation to the crystal axes and reciprocal lattice vectors. The right-hand inset shows the wire arrangement for the measurements of ${\rho }_c$. (c) In-plane field anisotropy ratio $\delta ={\rho }_c(H\parallel [1\overline{1}0])/{\rho }_c(H\parallel [110])$ for several field strengths. (d) Temperature derivative of resistivities for field along the $[1\overline{1}0]$ and [110] directions at 5 and 14 T.

Figure 2

Field dependence of the magnetoresistance $\mathit{\Delta }{\rho }_c/{\rho }_c(H=0)$ at (a) 2.5 K and (b) 300 K. The magnetoresistance at low temperature is much greater for field along the $[1\overline{1}0]$ direction. At 300 K, the magnetoresistance is nearly independent of the in-plane field direction and exhibits an $H^2$ dependence as indicated with the dotted curves.

Figure 3

The so-called Kohler plot: the magnetoresistance ratio versus field divided by the zero-field resistivity.

Figure 4

(a) Observed azimuthal field angle $\varphi$ dependence of the interlayer resistivity ${\rho }_c$ of ${\mathrm{PdCoO}}_2$ at 2 K, for ${\mu }_{0}H=5$, 10, and 14 T. (b) Calculated $\varphi$ dependence of ${\rho }_c$ at ${\mu }_{0}H=14\mathrm{T}$ and $\tau =1.0$, 0.2, and 0.02 ps, normalized by ${\rho }_c$ for $H\parallel [110]$. We also present ${\rho }_c$ at 1.0 ps for fields slightly tilted from the $ab$ plane with the broken curve. For this calculation, the field-rotation plane is assumed to be tilted by 3° from the $[1\overline{1}0]$ direction in the $ab$ plane to the [001] direction. The inset of (b) presents the Fermi surface cross section at $k_z=0$ for the first-principles (FP) band calculation and the tight-binding (TB) model. The solid hexagon indicates the first BZ for the hexagonal representation and the broken hexagon the first BZ for the rhombohedral representation. The latter is shown to present a larger portion of the FS.

Figure 5

Calculated field dependence of the out-of-plane magnetoresistance $\mathit{\Delta }{\rho }_c/{\rho }_c(H=0)$ for $\tau =1\mathrm{ps}$. The solid lines just connect the discrete calculated data points. The observed large anisotropy in $\mathit{\Delta }{\rho }_c/{\rho }_c(H=0)$ is well reproduced.