{"status":"ok","message-type":"work","message-version":"1.0.0","message":{"indexed":{"date-parts":[[2026,5,16]],"date-time":"2026-05-16T13:55:04Z","timestamp":1778939704609,"version":"3.51.4"},"reference-count":61,"publisher":"MDPI AG","issue":"2","license":[{"start":{"date-parts":[[2021,1,23]],"date-time":"2021-01-23T00:00:00Z","timestamp":1611360000000},"content-version":"vor","delay-in-days":0,"URL":"https:\/\/creativecommons.org\/licenses\/by\/4.0\/"}],"content-domain":{"domain":[],"crossmark-restriction":false},"short-container-title":["Symmetry"],"abstract":"<jats:p>FeSe is classed as a Hund\u2019s metal, with a multiplicity of d bands near the Fermi level. Correlations in Hund\u2019s metals mostly originate from the exchange parameter J, which can drive a strong orbital selectivity in the correlations. The Fe-chalcogens are the most strongly correlated of the Fe-based superconductors, with dxy the most correlated orbital. Yet little is understood whether and how such correlations directly affect the superconducting instability in Hund\u2019s systems. By applying a recently developed ab initio theory, we show explicitly the connections between correlations in dxy and the superconducting critical temperature Tc. Starting from the ab initio results as a reference, we consider various kinds of excursions in parameter space around the reference to determine what controls Tc. We show small excursions in J can cause colossal changes in Tc. Additionally we consider changes in hopping by varying the Fe-Se bond length in bulk, in the free standing monolayer M-FeSe, and M-FeSe on a SrTiO3 substrate (M-FeSe\/STO). The twin conditions of proximity of the dxy state to the Fermi energy, and the strength of J emerge as the primary criteria for incoherent spectral response and enhanced single- and two-particle scattering that in turn controls Tc. Using c-RPA, we show further that FeSe in monolayer form (M-FeSe) provides a natural mechanism to enhance J. We explain why M-FeSe\/STO has a high Tc, whereas M-FeSe in isolation should not. Our study opens a paradigm for a unified understanding what controls Tc in bulk, layers, and interfaces of Hund\u2019s metals by hole pocket and electron screening cloud engineering.<\/jats:p>","DOI":"10.3390\/sym13020169","type":"journal-article","created":{"date-parts":[[2021,1,25]],"date-time":"2021-01-25T12:28:31Z","timestamp":1611577711000},"page":"169","update-policy":"https:\/\/doi.org\/10.3390\/mdpi_crossmark_policy","source":"Crossref","is-referenced-by-count":14,"title":["Electronic Origin of Tc in Bulk and Monolayer FeSe"],"prefix":"10.3390","volume":"13","author":[{"ORCID":"https:\/\/orcid.org\/0000-0001-8074-0030","authenticated-orcid":false,"given":"Swagata","family":"Acharya","sequence":"first","affiliation":[{"name":"King\u2019s College London, Theory and Simulation of Condensed Matter, The Strand, London WC2R 2LS, UK"},{"name":"Institute for Molecules and Materials, Radboud University, NL-6525 AJ Nijmegen, The Netherlands"}]},{"given":"Dimitar","family":"Pashov","sequence":"additional","affiliation":[{"name":"King\u2019s College London, Theory and Simulation of Condensed Matter, The Strand, London WC2R 2LS, UK"}]},{"given":"Francois","family":"Jamet","sequence":"additional","affiliation":[{"name":"King\u2019s College London, Theory and Simulation of Condensed Matter, The Strand, London WC2R 2LS, UK"}]},{"given":"Mark","family":"van Schilfgaarde","sequence":"additional","affiliation":[{"name":"King\u2019s College London, Theory and Simulation of Condensed Matter, The Strand, London WC2R 2LS, UK"},{"name":"National Renewable Energy Laboratory, Golden, CO 80401, USA"}]}],"member":"1968","published-online":{"date-parts":[[2021,1,23]]},"reference":[{"key":"ref_1","doi-asserted-by":"crossref","first-page":"137","DOI":"10.1146\/annurev-conmatphys-020911-125045","article-title":"Strong Correlations from Hund\u2019s Coupling","volume":"4","author":"Georges","year":"2013","journal-title":"Ann. 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