Novel attractive pairing interaction in strongly correlated superconductors
release_ejcsvkoeavfvxigwf66bw35vti
by
Priyo Adhikary, Tanmoy Das
Abstract
Conventional and unconventional superconductivity, respectively,
arise from attractive (electron-phonon) and repulsive (many-body
Coulomb) interactions with fixed-sign and sign-reversal pairing
symmetries. Although heavy-fermions, cuprates, and pnictides are widely
believed to be unconventional superconductors, recent evidence in one of
the heavy fermion superconductor (CeCu<jats:inline-formula><jats:alternatives><jats:tex-math>_2</jats:tex-math><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:msub><mml:mi /><mml:mn>2</mml:mn></mml:msub></mml:math></jats:alternatives></jats:inline-formula>Si<jats:inline-formula><jats:alternatives><jats:tex-math>_2</jats:tex-math><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:msub><mml:mi /><mml:mn>2</mml:mn></mml:msub></mml:math></jats:alternatives></jats:inline-formula>)
indicate the presence of a novel conventional type pairing symmetry
beyond the electron-phonon coupling. We present a new mechanism of
attractive potential between electrons, mediated by emergent boson
fields (vacuum or holon) in the strongly correlated mixed valence
compounds. In the strong coupling limit, localized electron sites are
protected from double occupancy, which results in an emergent holon
fields. The holon states can, however, attract conduction electrons
through valence fluctuation channel, and the resulting doubly occupied
states with local and conduction electrons condenseas Cooper pairs with
onsite, fixed-sign, s-wave pairing symmetry. We develop the
corresponding self-consistent theory of superconductivity, and compare
the results with experiments. Our theory provides a new mechanism of
superconductivity whose applicability extends to the wider class of
intermetallic/mixed-valence materials and other flat-band metals.
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Stage
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Date 2019-12-09
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