Microscopic route to nematicity in ${\text{Sr}}_3{\text{Ru}}_2{\text{O}}_7$

An anisotropic metallic phase dubbed electronic nematic phase bounded by two consecutive metamagnetic transitions has been reported in the bilayer ruthenate ${\text{Sr}}_3{\text{Ru}}_2{\text{O}}_7$. It has also been shown that the nematic and the accompanying metamagnetic transitions are driven by an effective momentum-dependent quadrupole-type interaction. Here, we study the microscopic origin of such an effective interaction. To elucidate the mechanism behind the spontaneous Fermi-surface distortion associated with the nematic, we identify a simple tight-binding model based on $t_{2g}$ orbitals, spin-orbit coupling, and the rotation of ${\text{RuO}}_6$ octahedra as starting point, consistent with the Fermi surface obtained from recent angle-resolved photoemission data. Within an extended Hubbard model the nematic state, characterized by an anisotropy between the bands near $\left(\pm \pi ,0\right)$ and $\left(0,\pm \pi \right)$, then strongly competes with ferromagnetic order but pre-empts it via a finite nearest-neighbor interaction. We discuss experimental means to confirm our proposal.

Figure 1

(Color online) (a) Fermi surface of the single layer model. The crosses (dots) indicate the saddle points of the ${\gamma }_2\left({\gamma }_1\right)$ band. The band-structure parameters are $t_1=0.5,t_2=0.05,t_3=0.5,t_4=0.1,t_5=-0.03,t_6=0.05,\mu =0.575,\overline{g}=0.1,\lambda =0.1375$. (b) Fermi surface of the corresponding bilayer system with finite interlayer hopping between quasi-1D orbitals. (c) Total DOS near the Fermi level corresponding to (a). See main text for details.

Figure 2

(Color online) Effect of an external magnetic field on the band structure for field orientations (a) parallel to the $z$ axis and (b) parallel to the $x$ axis with $B=0.05$.

Figure 3

(Color online) Mean field phase diagram. The order parameters exhibit dramatic jumps, and the magnetization $M$ is shown as a red dashed line in the ${\Delta }_{\text{M}}$ panel. Panels (a)–(c) display the FS evolution of the nematic ${\gamma }_2$ band near $\left(\pm \pi ,0\right)/\left(0,\pm \pi \right)$ along the blue dashed line. See main text for details.