Direct Observation of the Multisheet Fermi Surface in the Strongly Correlated Transition Metal Compound ${\mathrm{ZrZn}}_2$

The existence of flat areas of a Fermi surface (FS), predicted by electronic structure calculations and used in models of both magnetically mediated and phonon-mediated Fulde-Ferrell-Larkin-Ovchinnikov superconducting states, is reported in the paramagnetic phase of the ferromagnetic superconductor ${\mathrm{ZrZn}}_2$ using positron annihilation. The strongly mass-renormalized FS sheet, dominating the Fermi level density of states, is seen for the first time. The delocalization of the magnetization is studied using measured and calculated magnetic Compton profiles.

Figure 1

(a) The experimental occupancy in the (100) plane of the repeated zone scheme. The colors range from black (low occupancy) to white (high occupancy). (b) Section (solid line) along the white line shown in (a), along with its first derivative (dashed line), used to locate the FS breaks (illustrated for band 27), indicated by the arrows.

Figure 2

The four sheets of FS of paramagnetic ${\mathrm{ZrZn}}_2$, obtained from the positron experiment.

Figure 3

FS from fully-relativistic (FR) and scalar-relativistic (SR) KKR calculations in the (001) plane of ${\mathrm{ZrZn}}_2$ [26]. The paramagnetic (PM) calculations are on the left-hand side, and the ferromagnetic (FM) ones are on the right. Note that the shading in the FM calculations indicates majority ($\uparrow$) / minority ($\downarrow$) spin. The magnetization axis is along [001].

Figure 4

Magnetic Compton profile along [100].