Z<sub>3</sub>-vestigial nematic order due to superconducting fluctuations in the doped topological insulators Nb<sub>x</sub>Bi<sub>2</sub>Se<sub>3</sub> and Cu<sub>x</sub>Bi<sub>2</sub>Se<sub>3</sub>.
basic_science · Level V
Where this comes from
- Record sourced from PubMed, PMID 32546839.
- Also identified by DOI 10.1038/s41467-020-16871-9 and PMC identifier 7298044.
- Licence recorded as CC BY.
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Abstract
A state of matter with a multi-component order parameter can give rise to vestigial order. In the vestigial phase, the primary order is only partially melted, leaving a remaining symmetry breaking behind, an effect driven by strong classical or quantum fluctuations. Vestigial states due to primary spin and charge-density-wave order have been discussed in iron-based and cuprate materials. Here we present the observation of a partially melted superconductivity in which pairing fluctuations condense at a separate phase transition and form a nematic state with broken Z<sub>3</sub>, i.e., three-state Potts-model symmetry. Thermal expansion, specific heat and magnetization measurements of the doped topological insulators Nb<sub>x</sub>Bi<sub>2</sub>Se<sub>3</sub> and Cu<sub>x</sub>Bi<sub>2</sub>Se<sub>3</sub> reveal that this symmetry breaking occurs at [Formula: see text] above [Formula: see text], along with an onset of superconducting fluctuations. Thus, before Cooper pairs establish long-range coherence at T<sub>c</sub>, they fluctuate in a way that breaks the rotational invariance at T<sub>nem</sub> and induces a crystalline distortion.