Direct Visualization of Electronic Liquid Crystal Phases in Correlated Topological Semimetals

Balaji Venkatesan^1,2, Syu-You Guan¹, Shiang-Bin Chiu², Jen-Te Chang¹, Po-Yuan Yang⁶, Chih-Chuan Su¹, Ming-Wen Chu³, Raman Sankar¹, Guoqing Chang⁵, Cheng-Yi Huang¹, Adrian Del Maestro⁴, Chia-Seng Chang^1,2, Tay-Rong Chang⁶, Hsin Lin¹, Ying-Jer Kao², Tien-Ming Chuang^1*

¹Institute of Physics, Academia Sinica, Taipei, Taiwan
²Department of Physics, National Taiwan University, Taipei, Taiwan
³Center for Condensed Matter Sciences, National Taiwan University, Taipei, Taiwan
⁴Department of Physics & Astronomy, University of Tennessee, Knoxville, TN, USA
⁵Division of Physics and Applied Physics, Nanyang Technological University, Singapore, Singapore
⁶Department of Physics, National Cheng-Kung University, Tainan, Taiwan

* Presenter:Tien-Ming Chuang, email:chuangtm@gate.sinica.edu.tw

Strongly correlated electron systems, in which various order parameters compete or intertwine with each other, exhibit rich quantum states of matter. Topological materials, which host symmetry protected Dirac or Weyl fermions, however, are mostly weakly correlated. Hence, the search for correlated topological materials has attracted great attention. Here, we report the first direct observation of electronic liquid crystal phases in nonsymmorphic topological semimetals by using scanning tunneling microscopy (STM). Real-space STM images reveal electronic nanostructures of incommensurate stripes and intense nematic order, which is reminiscent of the “checkerboard” pattern in underdoped cuprates. Quasiparticle scattering interference imaging also reveals linearly dispersive q-vectors, consistent with the calculated topological band structure. We further show the chemical substitution to the half-filled square-net layer plays the key role in the formation of electronic nematicity and also stabilizes unidirectional charge density wave instability towards incommensurate stripe order. Our results herein demonstrate these topological semimetals are strongly correlated and they provide a fertile playground for the study of novel phenomena of correlated Dirac electrons.

Keywords: Electron correlation, Topological semimetals, Scanning Tunneling Microscopy