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David Le Bolloc’h LPS Bât 510 OrsayVincent Jacques N. KirovaJean Dumas IN GrenobleS. Ravy Synchrotron Soleil
ECRYS 08
Observation of correlations up to the micrometer scalein sliding charge density waves.
Bleu bronze K0.3MoO3 by coherent X-ray diffraction
(Gaussien)
« Coherent diffraction » Transverse coherence length: x y
Longitudinal coherence length: l
Taille du faisceau
Helmholtz: ( +k )U=02 2
Degree of coherence :
z
D / 2 a
D
a
(Gaussien)
« Coherent diffraction » Transverse coherence length: l et t
Taille du faisceau
Helmholtz: ( +k )U=02 2
Degree of coherence :
z 1 !!
D / 2 a
D
10µm
ÅVisible light:
Source
Åa ~ 1mm
= D / 2 a
Source
Å
Å
2µm*2µm ~10 000
X-rays:
Rectangular aperture
D. Le Bolloc’h et al. J. Synchrotron Radiat. 9, 258 (2002).
Sr
O
II) Displacive phase transition: « central peak » and the « second length scale» in SrTi03
(3/2 1/2 ½) superstructure at Tc+10K central peakobserved by X-ray
Ravy, L.B.,Curat et al., PRL (2007)
superstructure (1/2 1/2 1/2)
(AuAgZn
2
)
F. Livet et al. PRB (2006)
I) Phase transition (order-desorder in metallic alloys)
Pd3VAuAgZn2
Narrow and broad component
Bronze bleu K0.3MoO3
2kF CDW
qc=a*0.752b*-0.5 c*
qc
Beam size
Beam size
10 Å
b
Theory:
Lee et Rice (1979)
Golkov (1983)
Ong and Maki (1985)
Freidel Feinberg
CDW Dislocation
Bulk CDW modulation
Bronze bleu K0.3MoO3
2kF CDW cos(qc r + )
D. Le Bolloc’h et al. prl (2005)
qc=a*0.752b*-0.5 c*
qc
Beam size
Beam size
10A
10µm
Cryostatccd
S2
fs
E=7.6Kev26.4°
ccd(6 0 –3)
2a*+c*
2a*-c*(8 0 –4)
(4 0 –4)
0.252 b*
12.6°
V10*10µm
QS (6 0.252 -3.5)
at 75K
Experimental setup:
Blue bronze under external current ?
2mm
DV
/DI
Is=1.2 mA
I (mA)
a) b)I=16*Is
I=16*IsI=0I=0
t
~ t*bb
2a*-c*
Each isosurface has been fixed at Imax/18 for the (6 0 -3) and Imax/7 for Qs. For clarity, the reflections with and without current have been shifted along b. The field-induced satellites are indicated by arrows. Each 3D acquisition lasted less than 15 mn.
QS (6 0.252 -3.5)
(6 0 -3)
2kF CDW Host lattice
1.2μm at I=0mA, 0.6μm at I=12 Is 0.4μm at I=16 Is
direction transverse :
T.Tamegai et al., Solid State Commun. 51, 585 (1984);R.M. Fleming, R.G. Dunn, L.F. Schneemeyer, Phys. Rev.B 31, 4099 (1985).
(6, 0.252 + qs, 3.5) with qs = 4.9 10−4 in b* units
L=1.5μm !!!1500*CDW (=4/3 b*=10.08A°)
qs
0 Cos[2kF+(x)]
(x)
Experimental data
=/4
Secondary fringes q
~1µm
d
2kF
Long range order up to the micrometer scalein sliding charge density waves.
Temperature dependence?Relationship with sliding ?Is it universal in CDW systems ?
D. Le Bolloc’h et al. Phys. Rev. Lett. 100, 096403 (2008)
Conclusions:
Vincent Jacques N. KirovaJean Dumas IN GrenobleS. Ravy Synchrotron Soleil
Poster « chromium »