80 research outputs found
Observation of the chiral anomaly induced negative magneto-resistance in 3D Weyl semi-metal TaAs
Weyl semi-metal is the three dimensional analog of graphene. According to the
quantum field theory, the appearance of Weyl points near the Fermi level will
cause novel transport phenomena related to chiral anomaly. In the present
paper, we report the first experimental evidence for the long-anticipated
negative magneto-resistance generated by the chiral anomaly in a newly
predicted time-reversal invariant Weyl semi-metal material TaAs. Clear
Shubnikov de Haas oscillations (SdH) have been detected starting from very weak
magnetic field. Analysis of the SdH peaks gives the Berry phase accumulated
along the cyclotron orbits to be {\pi}, indicating the existence of Weyl
points.Comment: Submitted in February'1
Interplay between multiple charge-density waves and the relationship with superconductivity in PdHoTe
HoTe, a member of the rare-earth tritelluride (Te) family, and
its Pd-intercalated compounds, PdHoTe, where superconductivity (SC)
sets in as the charge-density wave (CDW) transition is suppressed by the
intercalation of a small amount of Pd, are investigated using angle-resolved
photoemission spectroscopy (ARPES) and electrical resistivity. Two
incommensurate CDWs with perpendicular nesting vectors are observed in
HoTe at low temperatures. With a slight Pd intercalation ( = 0.01),
the large CDW gap decreases and the small one increases. The momentum
dependence of the gaps along the inner Fermi surface (FS) evolves from
orthorhombicity to near tetragonality, manifesting the competition between two
CDW orders. At = 0.02, both CDW gaps decreases with the emergence of SC.
Further increasing the content of Pd for = 0.04 will completely suppress
the CDW instabilities and give rise to the maximal SC order. The evolution of
the electronic structures and electron-phonon couplings (EPCs) of the multiple
CDWs upon Pd intercalation are carefully scrutinized. We discuss the interplay
between multiple CDW orders, and the competition between CDW and SC in detail.Comment: 6 pages, 5 figure
Low-energy spin excitations in optimally doped CaFeCoAsF superconductor studied with inelastic neutron scattering
There are few inelastic neutron scattering (INS) reports on the
superconducting single crystals of FeAs-1111 system, even though it was first
discovered in 2008, due to the extreme difficulty in large single crystal
growth. In this paper, we have studied the low-energy spin excitations in the
optimally electron-doped CaFeCoAsF single crystals with
= 21 K by INS. The resonance energy of the superconducting spin
resonant mode with = 12 meV amounts to 6.6
, which constitutes the largest
/ ratio among iron-based
superconductors reported to date. The large ratio implies a strong coupling
between conduction electrons and magnetic excitations in
CaFeCoAsF. The resonance possesses a magnonlike upward
dispersion along transverse direction due to the anisotropy of spin-spin
correlation length within plane in the normal-state, which points to a
spin fluctuation mediated sign-reversed wave pairing in
CaFeCoAsF
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