Electronic nematicity has been found in a range of correlated electron materials, exhibiting strong symmetry-breaking reconstruction of electronic states without a significant lattice distortion. An enigmatic example of an electronic nematic state is found in Sr₃Ru₂O₇, where a large resistivity anisotropy is stabilized by external magnetic field [1]. The direction of the anisotropy can be controlled by the in-plane component of the magnetic field, which was explained by field-induced spin density waves [2].

Recently, STM measurements have revealed symmetry breaking of the electronic structure at the surface of Sr₃Ru₂O₇ even in zero magnetic field, providing new insights into the mechanism stabilizing the nematicity [3].

Here, we use low-temperature scanning tunnelling microscopy to study the electronic structure in Sr₃Ru₂O₇ in vector magnetic fields. We find that the electronic structure is strongly affected even by relatively small external field, and is evolving continuously as a function of field direction. Quasiparticle interference measurements allow us to relate the observed angle dependence to the electronic structure of the material. We observe the electronic anisotropy at temperatures much higher than in the bulk, demonstrating its robustness.

This result establishes compass-like control over the electronic structure in the surface layer of Sr₃Ru₂O₇. The continuous evolution of the electronic structure with field direction cannot be easily explained by reorientation of a spin-density wave order but suggests that the field-controlled nematic state at the surface is driven by spin-orbit coupling [4].

 

[1] R. A. Borzi et al., Science 315, 214 (2007).

[2] C. Lester et al., Nature Materials 14 (2015)

[3] C. A. Marques et al., Sci. Adv. 8, eabo7757 (2022).

[4] S. Raghu et al., Phys. Rev. B 79, 214402 (2009)