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Title: Quadrupolar charge dynamics in the nonmagnetic FeSe 1−x S x superconductors
We use polarization-resolved electronic Raman spectroscopy to study quadrupolar charge dynamics in a nonmagnetic F e S e 1 − x S x superconductor. We observe two types of long-wavelength X Y symmetry excitations: 1) a low-energy quasi-elastic scattering peak (QEP) and 2) a broad electronic continuum with a maximum at 55 meV. Below the tetragonal-to-orthorhombic structural transition at T S ( x ) , a pseudogap suppression with temperature dependence reminiscent of the nematic order parameter develops in the X Y symmetry spectra of the electronic excitation continuum. The QEP exhibits critical enhancement upon cooling toward T S ( x ) . The intensity of the QEP grows with increasing sulfur concentration x and maximizes near critical concentration x c r ≈ 0.16 , while the pseudogap size decreases with the suppression of T S ( x ) . We interpret the development of the pseudogap in the quadrupole scattering channel as a manifestation of transition from the non-Fermi liquid regime, dominated by strong Pomeranchuk-like fluctuations giving rise to intense electronic continuum of excitations in the fourfold symmetric high-temperature phase, to the Fermi liquid regime in the broken-symmetry nematic phase where the quadrupole fluctuations are suppressed.  more » « less
Award ID(s):
1709161
NSF-PAR ID:
10227914
Author(s) / Creator(s):
; ; ; ; ;
Date Published:
Journal Name:
Proceedings of the National Academy of Sciences
Volume:
118
Issue:
20
ISSN:
0027-8424
Page Range / eLocation ID:
e2020585118
Format(s):
Medium: X
Sponsoring Org:
National Science Foundation
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