Electronic origin of T_c in bulk and monolayer fese

TY - JOUR

T1 - Electronic origin of Tc in bulk and monolayer fese

AU - Acharya, Swagata

AU - Pashov, Dimitar

AU - Jamet, Francois

AU - van Schilfgaarde, Mark

N1 - Funding Information: Acknowledgments: This work was supported by the Simons Many-Electron Collaboration. For computational resources, MvS, SA and DP acknowledge PRACE for awarding us access to SuperMUC at GCS@LRZ, Germany and Irene-Rome hosted by TGCC, France. SA acknowledges the Cambridge Tier-2 system operated by the University of Cambridge Research Computing Service (www.hpc.cam. ac.uk) funded by EPSRC Tier-2 capital Grant No. EP/P020259/1. Funding Information: This work was supported by the Simons Many-Electron Collaboration. For computational resources, MvS, SA and DP acknowledge PRACE for awarding us access to SuperMUC at GCS@LRZ, Germany and Irene-Rome hosted by TGCC, France. SA acknowledges the Cambridge Tier-2 system operated by the University of Cambridge Research Computing Service (www.hpc.cam. ac.uk) funded by EPSRC Tier-2 capital Grant No. EP/P020259/1. Publisher Copyright: Copyright: © 2021 by the authors. Licensee MDPI, Basel, Switzerland. Copyright: Copyright 2021 Elsevier B.V., All rights reserved.

PY - 2021/2

Y1 - 2021/2

N2 - FeSe is classed as a Hund’s metal, with a multiplicity of d bands near the Fermi level. Correlations in Hund’s 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’s 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 constrained 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’s metals by hole pocket and electron screening cloud engineering.

AB - FeSe is classed as a Hund’s metal, with a multiplicity of d bands near the Fermi level. Correlations in Hund’s 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’s 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 constrained 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’s metals by hole pocket and electron screening cloud engineering.

KW - Hund’s metals

KW - Spin susceptibilities

KW - Unconventional superconductivity

KW - Vertex functions

UR - http://www.scopus.com/inward/record.url?scp=85100886621&partnerID=8YFLogxK

U2 - 10.3390/sym13020169

DO - 10.3390/sym13020169

M3 - Article

AN - SCOPUS:85100886621

SN - 2073-8994

VL - 13

SP - 1

EP - 16

JO - Symmetry

JF - Symmetry

IS - 2

M1 - 169

ER -