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Title: Electronic Origin of Tc in Bulk and Monolayer FeSe

Journal Article · · Symmetry
DOI:https://doi.org/10.3390/sym13020169· OSTI ID:1770921
ORCiD logo [1];  [2];  [2];  [3]
  1. King's College, London (United Kingdom); Radboud Univ., Nijmegen (Netherlands)
  2. King's College, London (United Kingdom)
  3. King's College, London (United Kingdom); National Renewable Energy Lab. (NREL), Golden, CO (United States)

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 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’s metals by hole pocket and electron screening cloud engineering.

Research Organization:
National Renewable Energy Lab. (NREL), Golden, CO (United States)
Sponsoring Organization:
USDOE Office of Energy Efficiency and Renewable Energy (EERE); Simons Many-Electron Collaboration; Engineering and Physical Sciences Research Council (EPSRC)
Grant/Contract Number:
AC36-08GO28308; EP/P020259/1
OSTI ID:
1770921
Report Number(s):
NREL/JA-5F00-79447; MainId:33673; UUID:4e83d057-8122-48c1-a8c2-f036dede3657; MainAdminID:19960; TRN: US2206862
Journal Information:
Symmetry, Vol. 13, Issue 2; ISSN 2073-8994
Publisher:
MDPICopyright Statement
Country of Publication:
United States
Language:
English

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