Symmetry-breaking lattice distortion in Sr_3Ru_2O_7

TL;DR

This study reveals a subtle lattice distortion in Sr3Ru2O7 associated with its electronic nematic phase, showing how magnetic field orientation influences symmetry breaking and domain alignment, linked to quantum criticality.

Contribution

First observation of a structural relaxation driven by quantum criticality in Sr3Ru2O7, highlighting the interplay between lattice distortion and electronic nematic order near a metamagnetic quantum critical point.

Findings

Small lattice distortion (<10^-7) breaks four-fold symmetry at low angles.

Larger, area-preserving distortion (~2×10^-6) occurs at higher angles.

Distortion linked to orbital ordering and quantum criticality.

Abstract

The electronic nematic phase of Sr$_3$Ru$_2$O$_7$ is investigated by high-resolution in-plane thermal expansion measurements in magnetic fields close to 8 T applied at various angles $\Theta$ off the c-axis. At $\Theta<10^\circ$ we observe a very small ($10^{-7}$) lattice distortion which breaks the four-fold in-plane symmetry, resulting in nematic domains with interchanged $a$- and b-axis. At $\Theta \gtrsim 10^\circ$ the domains are almost fully aligned and thermal expansion indicates an area-preserving lattice distortion of order $2\times 10^{-6}$ which is likely related to orbital ordering. Since the system is located in the immediate vicinity to a metamagnetic quantum critical end point, the results represent the first observation of a structural relaxation driven by quantum criticality.