Electronic nematicity, a correlated state that spontaneously breaks rotational symmetry, is observed in several layered quantum materials. In contrast to their liquid-crystal counterparts, the nematic director cannot usually point in an arbitrary direction (XY nematics), but is locked by the crystal to discrete directions (Ising nematics), resulting in strongly anisotropic fluctuations above the transition. Here, we report on the observation of nearly isotropic XY-nematic fluctuations, via elastoresistance measurements, in hole-doped Ba1−xRbxFe2As2 iron-based superconductors. While for x = 0, the nematic director points along the in-plane diagonals of the tetragonal lattice, for x = 1, it points along the horizontal and vertical axes. Remarkably, for intermediate doping, the susceptibilities of these two symmetry-irreducible nematic channels display comparable Curie-Weiss behavior, thus revealing a nearly XY-nematic state. This opens a route to assess this elusive electronic quantum liquid-crystalline state.
|Original language||English (US)|
|Number of pages||6|
|Journal||Proceedings of the National Academy of Sciences of the United States of America|
|State||Published - Mar 24 2020|
Bibliographical noteFunding Information:
ACKNOWLEDGMENTS. We thank A. E. Böhmer, V. Borisov, A. Chubukov, A. Fujimori, Y. Gallais, H. Kontani, C. Meingast, S. Onari, I. Paul, J. Schmalian, Q. Si, and R. Valenti for fruitful discussion. This work was supported by Japan Society for the Promotion of Science Grants-in-Aid for Scientific Research JP19H00649, JP18K13492, and JP18H05227 and on Innovative Areas “Quantum Liquid Crystals” (Grants JP19H05823 and JP19H05824); and by the Tsukuba Innovation Arena “Kakehashi” collaborative research program. X-ray diffraction measurements were partly supported by the joint research in the Institute for Solid State Physics, the University of Tokyo. Theory work (R.M.F.) was supported by the US Department of Energy, Office of Science, Basic Energy Sciences Award DE-SC0012336.
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- Electronic nematicity
- Iron-based superconductors
- Nematic susceptibility