Condensed Matter Seminar Series
Overview of the Fe-based Superconductors
Maw-Kuen Wu
Institute of Physics, Academia Sinica, Nankang, Taipei, Taiwan
Monday November 23,
10:00 am,
Room 298, Physics Building
In
this presentation, I shall give an overview of the recent development
of the new Fe-based superconductor. Besides the general introduction to the
current
status of the new superconducting systems, I shall concentrate in the
current
understanding of the controlling parameters for the occurrence of
superconductivity in β-FeSe
system, which we
discovered to be superconducting last April. Particular emphasis will
be on the
doping effects, using group-IV elements to replace Se; and transition
metals to
replace Fe, on superconductivity. An anomaly at about 105K appears in
the
magnetic susceptibility measurement, which is also seen in the
resistive and
specific heat measurements though not as clear. This anomaly is found
closely
associated with the low temperature structural distortion that changes
the
materials from tetragonal symmetry to triclinic symmetry. More detailed
specific heat studies show that the electronic contribution to specific
heat
correlates well with the onset of superconducting transition
temperature. An
interesting magnetic feature observed at low temperature suggests an
anomalous
magnetic structure may associate with superconductivity. Magnetic field
dependence of the resistive transition in polycrystalline α-FeSe1-x and FeSe1-xTex
suggest
that Te-doping tends to induce the system to become more 2D-like and
enhances
substantially the upper critical field value, whereas the FeSe system
behaves
more like 3D superconductor.
Host: Albert Chang