dc.contributor.author Kostin, Andrey dc.date.accessioned 2018-10-23T13:21:48Z dc.date.available 2018-10-23T13:21:48Z dc.date.issued 2018-05-30 dc.identifier.other Kostin_cornellgrad_0058F_10773 dc.identifier.other http://dissertations.umi.com/cornellgrad:10773 dc.identifier.other bibid: 10489413 dc.identifier.uri https://hdl.handle.net/1813/59329 dc.description.abstract High temperature superconductivity is typically found in the vicinity of a magnetically ordered phase. The parent state of iron-based superconductors is most often a collinear antiferromagnet that breaks the tetragonal symmetry of the high temperature phase. Such a magnetically ordered state is accompanied by an orthorhombic lattice distortion and the nematic ordering of electronic degrees of freedom. Intriguingly, FeSe is an iron-based superconductor that realizes nematic ordering in the absence of any long range magnetic order. A recent scanning tunneling microscopy (STM) experiment deduced the superconducting gap structure of FeSe suggesting that in this material orbital selectivity plays a significant role in superconducting pairing. Within a multi-orbital Hubbard model for iron-based superconductors, such orbital selectivity is expected and driven by a sizable Hund's coupling. In this thesis, I use STM to visualize quasiparticle interference patterns in the unusual nematic state of FeSe. The analysis of these patterns demonstrates that the quasi-particle weight is significantly larger for the $d_{yz}$ orbitals than for the $d_{xz}$ and $d_{xy}$ orbitals. This establishes the existence of strong orbital-selective correlations in FeSe. Additionally, I identify significant directionality in the atomic structure of local density of states images in FeSe at low temperature. This is a novel method for visualizing nematicity in iron-based superconductors. dc.language.iso en_US dc.subject Condensed matter physics dc.subject Low temperature physics dc.subject FeSe dc.subject correlations dc.subject iron-based superconductors dc.subject orbital-selective dc.subject quasiparticle interference dc.subject STM dc.title STM Imaging of Strong Orbital-Selective Correlations in FeSe dc.type dissertation or thesis thesis.degree.discipline Physics thesis.degree.grantor Cornell University thesis.degree.level Doctor of Philosophy thesis.degree.name Ph. D., Physics dc.contributor.chair Davis, James C. dc.contributor.committeeMember McEuen, Paul L. dc.contributor.committeeMember Elser, Veit dcterms.license https://hdl.handle.net/1813/59810 dc.identifier.doi https://doi.org/10.7298/X4445JQT
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