David Le Bolloc’h LPS Bât 510 Orsay Vincent Jacques N. Kirova Jean DumasIN Grenoble S. RavySynchrotron Soleil ECRYS 08 Observation of correlations up to the micrometer scale in sliding charge density waves. Bleu bronze K 0.3 MoO 3 by coherent X-ray diffraction

(Gaussien) « Coherent diffraction » Transverse coherence length:  x  y Longitudinal coherence length:  l Taille du faisceau Helmholtz: (  +k )U=0 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=0 2 Degree of coherence  : z  1 !!  D / 2 a D 10µm

 Å Visible light: Source  Å a ~ 1mm  = D / 2 a Source  Å  Å 2µm*2µm ~  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 SrTi0 3 (3/2 1/2 ½) superstructure at T c +10K central peak observed by X-ray Ravy, L.B.,Curat et al., PRL (2007) superstructure (1/2 1/2 1/2) (AuAgZn2)(AuAgZn2) F. Livet et al. PRB (2006) I)Phase transition (order-desorder in metallic alloys) Pd 3 V AuAgZn 2 Narrow and broad component

Bronze bleu K 0.3 MoO 3 2k F CDW q c = a* 0.752b* -0.5 c* qcqc 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 K 0.3 MoO 3 2k F CDW    cos(q c r +  ) D. Le Bolloc’h et al. prl (2005) q c = a* 0.752b* -0.5 c* qcqc Beam size  Beam size  10A

10µm Cryostat ccd S2 fs E=7.6Kev 26.4° ccd (6 0 –3) 2a*+c* 2a*-c* (8 0 –4) (4 0 –4) b* 12.6° V 10*10µm Q S ( ) at 75K Experimental setup: Blue bronze under external current ? 2mm DV/DI I s =1.2 mA I (mA)

 a)b) I=16*I s I=0  tt ~ t* bb bb 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. Q S ( ) (6 0 -3) 2k F 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, q s, 3.5) with q s = −4 in b* units L=1.5μm !!! 1500* CDW (=4/3 b*=10.08A°) qsqs

 0 Cos[2k F +  (x)]  (x) Experimental data  =  /4 Secondary fringes qq ~1µm d 2k F

Long range order up to the micrometer scale in 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, (2008) Conclusions: Vincent Jacques N. Kirova Jean DumasIN Grenoble S. RavySynchrotron Soleil Poster « chromium »