Transcript Perturbation of the 57Fe quadrupole interaction at

CZUŁOŚĆ SPEKTROSKOPII MÖSSBAUEROWSKIEJ
NA PRZEJŚCIE DO NADPRZEWODNICTWA
W Ba0.6K0.4Fe2As2
A. K. Jasek1, K. Komędera1, A. Błachowski1, K. Ruebenbauer1,
Z. Bukowski2, J. G. Storey3,4, J. Karpinski5,6
1Zakład
Spektroskopii Mössbauerowskiej, Instytut Fizyki, Uniwersytet Pedagogiczny, Kraków, Polska
2Instytut Niskich Temperatur i Badań Strukturalnych, Polska Akademia Nauk, Wrocław, Polska
3Cavendish Laboratory, University of Cambrige, United Kingdom
4School of Chemical and Physical Sciences, Victoria University, Wellington, New Zealand
5Laboratory of Solid State Physics, ETH Zurich, Switzerland
6Institute of Condensed Matter Physics, EPFL, Lausanne, Switzerland
-----------------------------------------------------------------------------------------------------X Ogólnopolskie Seminarium Spektroskopii Mössbauerowskiej OSSM’2014
Wrocław, 15-18 czerwca 2014
Iron-based superconductor families
1111
122
111
LnO(F)FeAs
AFe2As2
AFeAs
Ln = La, Ce, Pr, Nd, Sm, Gd …
Tsc max = 56 K
A = Ca, Sr, Ba, Eu, K
47 K
11
FeTe(Se,S)
A = Li , Na
18 K
15 K
The aim of the experiment was to check whether the Mӧssbauer spectroscopy is
sensitive to the superconducting transition in Ba0.6K0.4Fe2As2.
Ba1-xKxFe2As2
parent compound
BaFe2As2
doping
K
superconductivity
Tsc=38K
Tetragonal unit cell of BaFe2As2 and phase diagram of Ba1-xKxFe2As2
Fig. 2. Resistivity of Ba1-xKxFe2As2
(x = 0.1-0.3)
Fig. 1. Resistivity of Ba0.6K0.4Fe2As2 plotted vs. temperature
Fig. 3. Lattice parameters of the series
Ba1-xKxFe2As2 (x = 0–0.3)
BaFe2As2 vs. Ba0.6K0.4Fe2As2
Fig. 3. The difference in total molar
specific heat coefficients
 stot   tot
p
between superconductor (s) and
parent compound (p) versus temperature
γtot=Ctot/T
Ctot- the total molar heat capacity
The inset shows the electronic
specific heat coefficient
 sel  C el / T
of the superconductor versus
temperature
Figs. 1,2. 57Fe Mössbauer spectra versus temperature for
the parent compound BaFe2As2 and the Ba0.6K0.4Fe2As2
Cel- the electronic molar heat capacity
Ba0.6K0.4Fe2As2
Tsc = 38 K
Selected Mössbauer spectra of the Ba0.6K0.4Fe2As2 across the transition to the superconducting state.
Note the abrupt changes in the regions 40 K - 38 K and 28 K - 24 K
A. K. Jasek et al., J. Alloys Comp. 609, 150 (2014)
Parameters derived from the Mössbauer spectra of Ba0.6K0.4Fe2As2
plotted versus temperature.
S
Δ0
Γ
tA
– total spectrum shift versus room temperature α-Fe
– constant component of the quadrupole splitting
– absorber line width
– dimensionless absorber resonant thickness
Ratio of the recoilless fractions f/f0
and dispersion of CDW Δρ versus temperature
Electric field gradient wave (EFGW) in Ba0.6K0.4Fe2As2
 - quadrupole coupling constant
N
   (q  r)   0    an cos[n(q  r)]  bn sin[n(q  r)] 
n 1
1
   (q  r)   0  AFmax
F (q  r)

 2  q  r 1 2 
 2  q  r 3 2  


F (q  r)  sin(q  r)  exp   
    exp   
  
4  
4   
 2
 2





A - amplitude of EFGW
β - shape parameter of EFGW
Shape of EFGW
Conclusions
•
CDW and modulation of the EFG on the iron nuclei develop within this
system.
•
The new type of hyperfine interaction modulation called electric field
gradient wave (EFGW) is seen on the iron nuclei.
•
The charge modulation is sensitive to the transition between normal and
superconducting state. CDW and EFGW strongly vary at the
superconducting gap opening.
•
A distribution of the “covalent” electrons is strongly perturbed by the itinerant
electrons forming Cooper pairs.
•
Dynamic properties of the iron nuclei seem unaffected by a transition to the
superconducting state.
Thank You
for Your attention