APS March Meeting 2014
Volume 59, Number 1
Monday–Friday, March 3–7, 2014;
Denver, Colorado
Session J40: Invited Session: Superconductivity and Magnetism of Iron-based Superconductors II
2:30 PM–5:30 PM,
Tuesday, March 4, 2014
Room: Mile High Ballroom 2B-3B
Sponsoring
Unit:
DCMP
Chair: Jeffrey W. Lynn, National Institute of Standards and Technology
Abstract ID: BAPS.2014.MAR.J40.1
Abstract: J40.00001 : Magnetism and its interplay with Superconductivity in the Doped Iron Chalcogenide Fe$_{\mathrm{1+y}}$Te$_{\mathrm{1-x}}$Se$_{\mathrm{x}}$
2:30 PM–3:06 PM
Preview Abstract
Abstract
Author:
Vivek Thampy
(Brookhaven National Lab)
I examine the relationship of iron superconductivity with impurities, and
low energy magnetic excitations in the structurally simple iron
superconductor, (Fe$_{\mathrm{1+y}}$Te$_{\mathrm{1-x}}$Se$_{\mathrm{x}})$.
In the first part of the talk, the pivotal role played by interstitial iron
impurities in the microscopic origin of the quasi-static magnetism at
(1/2,0) is demonstrated in Fe$_{\mathrm{1+y}}$Te$_{0}$ 0.38 [1].
We used polarized and unpolarized neutron scattering together with
simulations of the scattering function based on structural data and a
semi-metallic 5-band model with super-exchange interactions with the
interstitial iron, to show that the formation of magnetic polarons around
the interstitial iron atoms seeds the observed (1/2,0) magnetism. Though the
quasi-static magnetism occurs at (1/2,0), the low energy spin dynamics are
dominated by fluctuations at (1/2,1/2), like other iron based
superconductors.
In the second part of the talk, I will discuss these fluctuations and in
particular the so-called spin resonance -- the signature feature in the low
energy inelastic neutron scattering spectrum. We show that this scattering
is quasi two dimensional and largely isotropic. Further, the first moment
sum-rule for the dynamic correlation function is applied to the inelastic
data in the normal and superconducting states to quantitatively determine
the magnetic component of the superconducting condensation energy [2]. This
method is sensitive to changes in the inter-site magnetic correlation
energy, $\Delta $Eij, associated with superconductivity. We find that the
length scale over which $\Delta $Eij is appreciable is similar to the
superconducting coherence length, as determined by Scanning Tunneling
Microscopy. Comparison of the inter-site magnetic correlation energy to the
superconducting condensation energy determined through specific heat
measurements indicates a significant role of magnetic fluctuations in
stabilizing superconductivity.
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[1] V. Thampy et al, Phys. Rev. Lett. 108, 107002 (2012).\\[0pt]
[2] J. Leiner et al, Manuscript under preparation.
To cite this abstract, use the following reference: http://meetings.aps.org/link/BAPS.2014.MAR.J40.1