Magnetic-Field Tunable Intertwined Checkerboard Charge Order and Nematicity in the Surface Layer of Sr2 RuO4.

Carolina A Marques,Rosalba Fittipaldi,Renato Buzio,Peter Wahl,Andrea Gerbi,Veronica Granata,Chi Ming Yim,Antonio Vecchione,Andreas W Rost,Luke C Rhodes

doi:10.1002/adma.202100593

Abstract

In strongly correlated electron materials, the electronic, spin, and charge degrees of freedom are closely intertwined. This often leads to the stabilization of emergent orders that are highly sensitive to external physical stimuli promising opportunities for technological applications. In perovskite ruthenates, this sensitivity manifests in dramatic changes of the physical properties with subtle structural details of the RuO6 octahedra, stabilizing enigmatic correlated ground states, from a hotly debated superconducting state via electronic nematicity and metamagnetic quantum criticality to ferromagnetism. Here, it is demonstrated that the rotation of the RuO6 octahedra in the surface layer of Sr2 RuO4 generates new emergent orders not observed in the bulk material. Through atomic-scale spectroscopic characterization of the low-energy electronic states, four van Hove singularities are identified in the vicinity of the Fermi energy. The singularities can be directly linked to intertwined nematic and checkerboard charge order. Tuning of one of these van Hove singularities by magnetic field is demonstrated, suggesting that the surface layer undergoes a Lifshitz transition at a magnetic field of ≈32T. The results establish the surface layer of Sr2 RuO4 as an exciting 2D correlated electron system and highlight the opportunities for engineering the low-energy electronic states in thesesystems.

Highlights

The physical properties of strongly corlization of emergent orders that are highly sensitive to external physical stimuli promising opportunities for technological applications
We show that the surface layer of Sr2RuO4 provides a 2D model system to study the intricate structure–property relationships of a strongly correlated electron system
We demonstrate the equivalence of checkerboard charge order and nematicity in this system, and find that the reconstructed electronic structure leads to four vHss within 5 meV of the Fermi energy

Summary

Introduction

The physical properties of strongly corlization of emergent orders that are highly sensitive to external physical stimuli promising opportunities for technological applications. The singularities can related electron materials often vary dramatically with comparatively modest external stimuli,[1] evidenced, for example, by magnetic-field driven metamagnetic transitions,[2,3] doping-induced metal-toinsulator transitions[4] and superconductivity[5] as well as a surprising sensitivity to uniaxial strain.[6] The changes in physical properties are usually accompanied by tiny structural distortions often reflecting, or even inducing, the lower symmetry of the new electronic states This sensitivity of physical properties is exemplified in be directly linked to intertwined nematic and checkerboard charge order. Its bulk Fermi surface has been established by quantum oscillations[15] and confirmed by angle-resolved photo emission spectroscopy (ARPES).[14,16,17]

Results

Discussion

Conclusion