Novel electronic nematicity in heavily hole-doped iron pnictide superconductors.
basic_science · Level V
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- Record sourced from PubMed, PMID 32165540.
- Also identified by DOI 10.1073/pnas.1909172117 and PMC identifier 7104219.
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Abstract
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 Ba<sub>1-<i>x</i></sub> Rb <i><sub>x</sub></i> Fe<sub>2</sub>As<sub>2</sub> iron-based superconductors. While for [Formula: see text], the nematic director points along the in-plane diagonals of the tetragonal lattice, for [Formula: see text], 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.