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Fermi-surface of underdoped LaFeAsO1-xFx as determined by the Haas-van Alphen-effect | | G. Li
; B. S. Conner
; S. Weyeneth
; N. D. Zhigadlo
; S. Katrych
; Z. Bukowski
; J. Karpinski
; D. J. Singh
; M. D. Johannes
; L. Balicas
; | | Date: |
7 Sep 2010 | | Abstract: | Here, we present a de Haas-van Alphen (dHvA) effect1 study on the newly
discovered LaFeAsO1-xFx compounds2,3 in order to unveil the topography of the
Fermi surface associated with their antiferromagnetic and superconducting
phases, which is essential for understanding their magnetism, pairing symmetry
and superconducting mechanism. Calculations 4 and surface-sensitive
measurements 5,6,7 provided early guidance, but lead to contradictory results,
generating a need for a direct experimental probe of their bulk Fermi surface.
In antiferromagnetic LaFeAsO1-xFx 8,9 we observe a complex pattern in the
Fourier spectrum of the oscillatory component superimposed onto the magnetic
torque signal revealing a reconstructed Fermi surface, whose geometry is not
fully described by band structure calculations. Surprisingly, several of the
same frequencies, or Fermi surface cross-sectional areas, are also observed in
superconducting LaFeAsO1-xFx (with a superconducting transition temperature Tc
~ 15 K). Although one could attribute this to inhomogeneous F doping, the
corresponding effective masses are largely enhanced with respect to those of
the antiferromagnetic compound. Instead, this implies the microscopic
coexistence of superconductivity and antiferromagnetism on the same Fermi
surface in the underdoped region of the phase diagram of the LaFeAsO1-xFx
series. Thus, the dHvA-effect reveals a more complex Fermi surface topography
than that predicted by band structure calculations4 upon which the currently
proposed superconducting pairing scenarios10,11,12,13 are based, which could be
at the origin of their higher Tcs when compared to their phosphide analogs. | | Source: | arXiv, 1009.1408 | | Services: | Forum | Review | PDF | Favorites | |
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