Coexistence and Competition of Magnetism and Superconductivity on the Nanometer Scale in UnderdopedBaFe1.89Co0.11As2

Abstract

We report muon spin rotation (μSR) and infrared spectroscopy experiments on underdoped BaFe1.89Co0.11As2 which show that bulk magnetism and superconductivity (SC) coexist and compete on the nanometer length scale. Our combined data reveal a bulk magnetic order, likely due to an incommensurate spin density wave (SDW), which develops below T(mag)≈32 K and becomes reduced in magnitude (but not in volume) below Tc=21.7 K. A slowly fluctuating precursor of the SDW seems to develop already below the structural transition at T(s)≈50 K. The bulk nature of SC is established by the μSR data which show a bulk SC vortex lattice and the IR data which reveal that the majority of low-energy states is gapped and participates in the condensate at T≪T(c).

Muon spin rotation study of magnetism and superconductivity in Ba(Fe1−xCox)2Bernhard1, Wang2, Nuccio3 et al. 2012Phys. Rev. BSelf Cite5422871View full textAdd to dashboardCite

“…We remark that our results confirm previous μSR work which already reported the coexistence and competition of bulk magnetic and superconducting orders for the underdoped sample at x = 0.055 (Ref. 15) as well as the development of an inhomogeneous magnetic state right below T c in a near-optimally doped sample. 24 …”

“…A true coexistence and competition between short-ranged but bulk AF order and superconductivity has been established in underdoped samples of Sm-1111 11,12 and especially in single crystals of Ba(Fe 1−x Co x ) 2 As 2 . [13][14][15][16] Such a coexistence was not observed in La-1111. 17 Moreover, in Ba 1−x K x Fe 2 As 2 (Refs.…”

“…[27][28][29][30][31] The x = 0.055 sample has been already previously investigated with μSR and infrared spectroscopy. 15 Infrared measurements have also been performed at x = 0.065. 32 Specific heat measurements on crystals from the same or similar growth batches are reported in Ref.…”

Visualizing the microscopic coexistence of spin density wave and superconductivity in underdoped NaFe1−xCoxAs

“…5) and BaFe 2 À x Co x As 2 (ref. 8), together with nuclear magnetic resonance 6 and neutron scattering 7 on similar compounds, reveal the coexistence of the two phases. In an intermediate case, neutron scattering in CeFeAsO 1 À x F x reveals a continuous transition, but the SDW and SC regimes only touch at a quantum critical point 3 .…”

“…A key question here is whether the magnetic order and superconductivity can coexist microscopically or mutually exclude each other. So far the available experimental methods used to answer this question are either spatially averaged probes or local ones without control of probing position, thus a consensus is still lacking [3][4][5][6][7][8][9] . Experiments on various iron pnictide compounds have revealed at least three categories of behaviour.…”