Optical properties of metallic ferromagnet Fe x -TaS 2 Overview: • Why Fe x -TaS 2 ? • Optical response • Observation of Symmetry- breaking effect S. Fan 1 , I.Manuel 2 , A. B. al-Wahish 1 , K. A. Smith 1 , K. R. O’Neal 1 , Y. Horibe 3 , S. W. Cheong 3,4 , J. T. Haraldsen 2 , and J. L. Musfeldt 1 1 University of Tennessee 2 University of North Florida 3 Rutgers University 4 Pohang University of Science and Technology Phys. Rev. B , 96, 205119 (2017).
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Optical properties of metallic ferromagnet Fex-TaS2
Overview:
• Why Fex-TaS2?
• Optical response
• Observation of Symmetry-
breaking effect
S. Fan1, I.Manuel2, A. B. al-Wahish1, K. A. Smith1, K. R. O’Neal1, Y. Horibe3 , S. W. Cheong3,4, J. T. Haraldsen2, and J. L. Musfeldt1
1University of Tennessee2University of North Florida
3Rutgers University4Pohang University of Science and Technology
Phys. Rev. B , 96, 205119 (2017).
Why FexTaS2 interesting?
P63/mmc P63/mmc P6322
S. Fan et. al. Phys. Rev. B (2017), Y. Horibe, J. Am. Chem. Soc. (2014)
Why interesting?• Quasi 2D material, which shows the existence
of CDW phase and long range magnetic ordering.
• Superlattice structure and interesting interface effect.
• Room temperature domain patterns
Antiphase + chiral domain wall
Antiphase domain wall
Fe1/4TaS2
Fe1/3TaS2
The chiral structure of Fe1/3TaS2 Top view of Fe1/3-TaS2
Y. Horibe, J. Am. Chem. Soc. (2014)
TaFeS
• The intercalation of Fe between Van der Waals gap breaks the inversion symmetry and brings the chirality of the crystal structure.
• All systems are metallic• Ta + Fe Drude
Free carrier response of Ta and Fe d orbital
Fe induced conductivity
2H-TaS2 data is from W. Z. Hu Phys. Rev. B (2007)
Fe bands involved in localized excitations
Signature of chirality
Centrosymmetric
Non-centrosymmetric
X = 0
X = 1/3
X = 1/4
• hole pocket e pocket at K-point is the signature of chirality
Signature of chirality
Oscillator strength and peak position analysis indicate the peaks are assigned as electronic excitations rather than phonons.
Summary• Intercalation of Fe brings a weak conductivity in the Van der Waals gap.
• Chirality structure has an strong influence of electronic properties.
• Spectroscopy provides a microscopic probe for the symmetry-breaking effect at the interface.
X = 1/3
We thank Department of Energy for support this work.
Collaborators
Janice Musfeldt
Sang Wook Cheong
Jason Haraldsen
Supplemental:Drude response of Fe1/3-TaS2
X = 0
X = 1/3
• Two Drude functions• A well isolated free carrier
response in Fe layer and TaS2 sheet
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