Scanning tunneling microscopy observation of electronic nematicity in the correlated Dirac semimetal BaNiS₂

Christopher Butler^1*, Y. Kohsaka¹, M. S. Bahramy², Y. Yamakawa³, S. Onari³, H. Kontani³, T. Hanaguri¹, S. Shamoto^4,5

¹CEMS, RIKEN, Wako, Saitama, Japan
²Dept. of Physics & Astronomy, University of Manchester, Manchester, UK
³Dept. of Physics, Nagoya University, Nagoya, Japan
⁴Neutron Science and Technology Center, CROSS, Ibaraki, Japan
⁵Dept. of Physics, National Cheng Kung University, Tainan, Taiwan

* Presenter:Christopher Butler, email:christopher.butler@riken.jp

BaNiS₂ is a quasi-two-dimensional Dirac semimetal whose low-energy electronic structure is mainly composed of Ni d orbitals, and significant correlations among these are expected to result in interesting correlated or non-Fermi liquid behaviors. Using scanning tunneling microscopy, we first characterize the surface band structure by observing quasiparticle interference and the emergence of Landau quantization within the Dirac cones. Additionally, both in observations of quasiparticle interference and in detailed intra-unit-cell spectroscopy, we observe a lowering of in-plane symmetry from the expected C_4v surface symmetry of the P4/nmm space group, to C_2v. These results indicate a bond-order nematicity reminiscent of that in the Fe-based superconductors, but among orbitals largely of d_z² character. This nematicity may be understood as emerging from interference between spin fluctuations within the Ni square net.

Keywords: Dirac semimetal, Electronic correlations, Nematicity, Quasiparticle interference, Scanning tunneling microscopy