V. METALLIC STRIPES COEXIST WITH SUPERCONDUCTIVITY

 "The dynamic JT phase could be realized as a pattern of LTT-type domains separated by dynamic domain walls. Bianconi and Missori (459a) have developed a similar model to explain the in-plane structure associated with the 1D CDW that they had deduced from earlier EXAFS observations in Bi2212 (460).
They find two in-plane Cu-O bonds lengths, assume that the longer one is associated with LTT domains. From the relative fraction of long bonds, they estimate the LTT fraction, and by measuring the period of the incommensurate modulation in Bi2212 by electron and X-ray diffraction, they can reconstruct the striped phase " polaronic CDW" Fig.49d. For P<0.06 they find all the holes go to LTT stripes, while for higher doping the holes are added to the LTO phase (459b).
Similar EXAFS data have now been reported (440) for LSCO (x=0.15) and again interpreted in terms of alternating LTO and LTT stripes.
459a) A. Bianconi and M. Missori, in "Phase Separation in Cuprate Superconductors" edited by E. Sigmund and K. A. Müller, Springer Verlag, Berlin-Heidelberg (1994) pag.272, A. Bianconi, M. Missori J. Phys. I (France) 4, 361 (1994);
459b) A. Bianconi Sol. State Commun. 91, 1 (1994)
460) A. Bianconi in "International Conference on Superconductivity", edited by S. K.Joshi CNR Rao, & S. V. Subramanyam, World Scientific Singapore pag. 448 (1990)
440) A. Bianconi N. L Saini, A. Lanzara, M. Missori, T. Rossetti, H. Oyanagi, H. Yamaguchi, K. Oka, T. Ito Phys. Rev. Lett 76, 3412-3415 (1996)"

Excerpt from the review by R.S. Markiewicz "A Survey of the Van Hove scenario for high T_c supereconductivity with special emphasis on pseudogaps and stripes phases" published in J. Phys. Chem Solids Vol. 58, pp. 1179-1310 (1997), (page 1237).
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"This configurations for 5 copper center polarons minimizes the elastic strain energy within a chain by retaining a maximum of only 4 copper centers in any cross sectional direction. In this configuration, the chains from stripes the <110> direction, and experimental evidence for such <110> stripes has been reported quite independently by Bianconi" (9)
9) A. Bianconi Sol. State Commun. 91, 1 (1994)

 Excerpt from the paper "Non adiabatic Electron-Lattice Interaction in the Copper Oxide Superconductors" by J.-S. Zhou, G.I. Bersuker, and J.B. Goodenough
Journal of Superconductivity. Vol. 8 No.5 1995 pag. 541-544
(in the special issue for the procedings of the University of Miami workshop on high temperature superconductivity held on Coral Gables FL Jan 5-11 (1995))
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"Recent experimental investigation of the mesoscopic structure of cuprate superconductors by x-ray absorption (EXAFS), neutron scattering and other techniques have provided increasing evidence of charge ordering in the inhomogeneous CuO₂ plane, giving rise to a superlattice of alternating quantum stripes in the CuO₂ plane with an approximate width of 10Å. (16). If one considers there to be two different kinds of charge carriers in the alternating stripes, i.e., small-(bi)polaronic-type charge carriers in stripes A and Fermi-liquid-type carriers in stripes B (6,17), one may be able to explain the spin susceptibility data very well, as will be shown here."

Excerpt from K. A. Müller, Guo-meng Zhao, K. Conder, and H. Keller
"The ratio of small polarons to free carriers in La _2-x Sr_xCuO₄ derived from susceptibility measurements " J. Phys. Condens. Matter 10 (1998) L291-L296
see pag. L293 (see also D. Mihailovich and K. A. Müller in High T_c Superconductivity (1996): Ten years after the Discovery (Nato Asi Series A: Series E Applied Sciences, Vol. 343) ed. E. Kaldis, E. Liarokapis and K. A. Müller (Dordrecht, Kluwer) pag. 243)
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"Using extended x-ray absorption fine structure (EXAFS) Bianconi et al. (18) have observed polaronic stripes in the Bi2212 material in which polarons order into stripes"
(18) A. Bianconi and M. Missori, Proc. of the Workshop held at Cottbus, Germany, Sept 4-10, 1993 in "Phase Separation in Cuprate Superconductors" edited by E. Sigmund and K. A. Müller, Springer Verlag, Berlin-Heidelberg (1994) pag. 272-289.

Excerpt from the paper "Oxygen ordering and phase separation in La₂CuO_4+d" by B. W. Statt, P. C. Hammel, Z. Fisk, S. W. Cheong, F. C. Chou, D. C. Johnston and J. E. Schirber, Phys. Rev. B 52, 15575 (1995) isuue of 1 DIC 1995
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"A complete determination of the local structure around the Cu atoms in the CuO₂ planes of high temperature superconductors with enough resolution to distinguish a complex multisite radial distribution function from a simple Gaussian distribution has been made in few cases like Bi2Sr2CaCu2O8+y (10 ) and La_1.85Sr_0.15CuO₄(3)"
(10) A. Bianconi, S. Della Longa, M. Missori, I. Pettiti, M. Pompa in "Lattice Effects in High-Tc Superconductors, edited by Y. Bar-Yam, T. Egami, J. Mustre-de Leon, & A. R. Bishop, World Scientific Pub., Singapore, pag. 65-76 (1992)
(3) Local Lattice Instabillity of CuO2 plane in La 1.85Sr0.15CuO4 by Polarized Cu K edgeAbsorption s N.L. Saini, A. Lanzara, M. Missori, T. Rossetti, A. Bianconi, H. Oyanagi, H. Yamaguchi, K. Ota, and T. Ito Physica C 251, 383 (1995); A. Bianconi N. L Saini, A. Lanzara, M. Missori, T. Rossetti, H. Oyanagi, H. Yamaguchi, K. Oka, T. Ito Phys. Rev. Lett 76, 3412-3415 (1996).

"Also experimental evidence for the ordering of these phases into stripe ordered regions has been presented "(4)
(4) A. Bianconi, M. Lusignoli, N. L. Saini, P. Bordet, Å. Kvick, P. G. Radaelli Phys. Rev. B 54 4310 (1996).

Excerpt from the paper by S. D. Conradson, J. Munstre De Leon and A. R. Bishop
"Local phase separation in Tl based oxide superconductors" published on J. of Superconductivity Vol. 10, pag. 329 (1997)
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"Recent EXAFS measurements (5) provides evidence for stripes in La_1.85Sr_0.15CuO₄(5)"
(5) A. Bianconi N. L Saini, A. Lanzara, M. Missori, T. Rossetti, H. Oyanagi, H. Yamaguchi, K. Oka, T. Ito Phys. Rev. Lett 76, 3412-3415 (1996).

Excerpt from the paper by P. C. Hammel, B.W. Statt, R.L. Martin, F.C.Chou, D.C. Johnston, and S.-W.Cheong "Localized holes in Superconducting Lanthanum Cuprates" Phys. Rev. B Vol. 57 pag, 712 (1998).
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"Recently stripe phase [7] in ab plane of the La₂CuO_4+dsystem was observed when the oxygen doping content is well beyond the phase separation range"
[7] A. Lanzara, N. L. Saini, A. Bianconi, J. L. Hazemann,, Y. Soldo, F. C. Chou, and DC. Johnston Phys. Rev. B 55, 9120-9124 (1997)Excerpt from the paper "Direct observation of Incommensurate Modulations in Phase Separated Cu rich La2CuO4.003" by X. L. Dong, Z. F. Dong, B. R. Zhao, Z. X. Zhao, X. F. Duan, L. -M. Peng, W. W. Huang, B. Xu, Y. Z. Zhang, S. Q. Guo, L. H. Zhao and L. Li Phys. Rev. Letters 80, 2701-2704 (1998).
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"The search for the lattice distortion associated with JT polarons of Q₂ variety pushed the Rome group in 1989 in collaboration with Calestani in Parma to solve the complete incommensurate structural modulation of the CuO2 plane by single crystal x-ray diffraction. The results have shown an intrinsic modulation of the CuO2 lattice due to ordering of the CuO4 square lattice distortions.
Previous works have shown other two contributions to the superstructure spots in diffraction 1) the in plane longitudinal compression wave in the Bi-O plane (by x-ray diffraction [Y. Gao, P. Lee, P. Coppens, M. A. Subramanian, A. W. Sleight Science 24, 954 (1988)] and the ordering of interstitial oxygens in lines the (1,1) diagonal direction in the Bi₂O₂ layers observed by neutron diffraction [E.A. Hewatt J.J. Capponi, and M. Marezio Physica C 157 502 1989].
The intrinsic modulation of the CuO₂ plane shows a one dimensional (1D) modulation of the orbital angular momentum i.e., a 1D orbital density wave (1D-ODW). These results have been confirmed by the joint use of electron diffraction and high resolution EXAFS for measure of the 1D modulation of the Cu-O(apical) bond, manly due to the dispacement of the Cu ions out the plane. In fact also this displacement is a good probe of the mixing of orbital angular momentum components ml=0 (different from the Cu 3d ml=2) Further refining of these measurements let us to the measure of the stripe width L and their separation W in Bi2212 by joint EXAFS and electron diffraction. Finally using anomaolus X-ray diffraction the anharmonic displacement of the Cu ion out of the oxygen plane, associated with an increasing mixing of the ml=0 orbital momentum has been determined, giving a compelling and definitive experimental evidence for the ODW and polaronic CDW in the (1,1) direction with a large second harmonic content."

Excerpt from "The stripe-scenario in cuprate superconductors" presented at the second Int. Conference in Stripes and high Tc superconductivity" by A Bianconi in "Stripes and Related Phenomena" Plenum Press.  see more by this: in A. Bianconi, P. Castrucci, M. De Simone, A. Di Cicco, A. Fabrizi, C. Li, M. Pompa, D. Udron, A. M. Flank, P. Lagarde, and G. Calestani in Proc. of the 3rd SATT meeting, Genova Feb. 12-14, 1990 "High Temperature Superconductivity" edited by C. Ferdeghini and A. S. Siri, World Scientific Co, Singapore, pp. 144-148 (1990);
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see more by this: in A. Bianconi in Proc. of the "International Conference on Superconductivity", held in Bangalore India Jan 10-14, 1990, edited by S. K. Joshi CNR Rao, & S. V. Subramanyam, World Scientific Singapore pag. 448 (1990).
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see more by this:in "Non homogeneous Cu site structure configurations and Cu apical oxygen vibrations at the normal to superconductor transition" A. Bianconi, S. Della Longa, M. Missori, I. Pettiti, M. Pompa in "Lattice Effects in High-T_c Superconductors, edited by Y. Bar-Yam, T. Egami, J. Mustre-de Leon, & A. R. Bishop, World Scientific Pub., Singapore, pag. 65-76 (1992)
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see more by this in "Linear arrays of non homogeneous Cu sites in the CuO2 plane: a new scenario for pairing mechanisms in a corrugated iron like plane" by A. Bianconi in Proc. of the workshop, held at Erice May 6-12,1992,in "Phase Separation in Cuprate Superconductors, edited by K. A. Muller, and G. Benedek, World Scientific Pub., Singapore, pp. 125-138 and at pag. 352 (1993)
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see more by this in "Structure of the different Cu sites in the corrugated CuO₂ plane in high T_c superconductors"A. Bianconi S. della Longa M. Missori, I. Pettiti, M. Pompa, and A. Soldatov Jpn. J. Appl. Phys. 32 (1993) Suppl. 32-2 pp. 578-580
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see more by this in A. Bianconi, M. Missori, H. Oyanagi, H. Yamaguchi, D.H. Ha, & Y. Nishihara, in published in the ETL Bulletin
Bianconi, M. Missori, H. Oyanagi, H. Yamaguchi, D. H. Ha, Y. Nishihara Bulletin of the Electrotechnical Laboratory Vol. 8 n.6 pag. 16, 1994) Proc. of ETL Workshop on High Temperature Superconductors (Tsukuba, Ibaraki, Japan Dec. 6-8 1993)
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see more by this in "Polaron size and ordering by x-ray absorption: The quantum confinement of a 2D-Fermi liquid giving high T_c superconductivity"
(Invited Talk at the SPIE Conference, Los Angeles, California, USA, January 24-28, 1994)
A. Bianconi, M. Missori, H. Oyanagi and H. Yamaguchi
in Oxide Superconductors Physics and Nano-Engineering, D. Pavuna Ed., SPIE Washington, 1994) Vol. 2158 pag.78-85
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see more by this in The measurement of the polaron size in the metallic phase of cuprate superconductors by A. Bianconi, M. Missori, H. Oyanagi, H. Yamaguchi, D. H. Ha, Y. Nishiara and S. Della Longa Europhys. Lett. 31, 411-415 (1995)
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see more by this in Stripe structure of the CuO₂ plane in Bi2Sr2CaCu2O8 by anomalous X-ry diffraction Bianconi, M. Lusignoli, N. L. Saini, P. Bordet, Å. Kvick, P. G. Radaelli Phys. Rev. B 54 4310 (1996).
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see more by this in A. Bianconi, N.L. Saini, T. Rossetti, A. Lanzara, A. Perali, M. Missori Stripe Structure in the CuO2 plane of perovkite superconductors Phys. Rev. B 54 12018 -12021 (1996)
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see more by this:in N.L. Saini , A. Lanzara, A. Bianconi , H. Oyanagi, H. Yamaguchi, K. Ota, T.Ito Temperature dependent Cu-O distribution function of the superconducting CuO2 plane Physica C 268 , 121-127 (1996)------------------------
see more by this:in N.L. Saini, A. Lanzara, H. Oyanagi, H. Yamaguchi, K. Oka and T. Ito A. Bianconi.Local Lattice Instability and Stripes in the CuO2 Plane of the La1.85Sr0.15CuO4 System by Polarized XANES and EXAFS. Phys. Rev.B 55, 12759-12769 (1997)
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see more by this:in A. Lanzara, N.L. Saini, A. Bianconi, J.L. Haemann, , Y. Soldo, F.C. Chou, and DC. JohnstonTemperature dependent modulatin amplitude of the CuO2 superconducting plane in La2CuO4.1Phys. Rev. B 55, 9120-9124 (1997)
From a homogeneous CuO2 plane to a superlattice of quantum stripes
A. Bianconi, N. L. Saini, A. Lanzara, A. Perali, and A. Valletta,
High T_c superconductivity 1996 Ten years after the discovery edited by E. Kaldis, E. Liarokapis,
and K. A. Müller NATOASI Series E, vol. 343 pag. 383-403

VI. A METAL NEAR THE WIGNER LOCALIZATION LIMIT

 "The Coupling of a Wigner Charge Density Wave with Fermi Liquid from the Instability of a Wigner Polaron Crystal:A Possible Pairing Mechanism in High Tc Superconductors"
A. Bianconi and M. Missori, Proc. of the Workshop held at Cottbus, Germany, Sept 4-10, 1993 in "Phase Separation in Cuprate Superconductors" edited by E. Sigmund and K. A. Müller, Springer Verlag, Berlin-Heidelberg (1994) pag. 272-289.
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"On the Fermi Liquid Coupled with a Generalized Wigner Polaronic CDW Giving High T_c Superconductivity"
A. Bianconi Sol. State Commun. 91, 1 (1994)
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 "The instability of a 2D Electron Gas Near the Critical Density for a Wigner Polaron Crystal Giving the Quantum State of Cuprate Superconductors"
A. Bianconi, M. Missori
Sol. State Commun. 91, 287 (1994)

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"The Instability Close to the 2D Generalized Wigner Polaron Crystal Density: A Possible Pairing Mechanism Indicated by a Key Experiment"
A. Bianconi, Invited talk at the int. conf. Materials and Mechanisms of Superconductivity, High Temperature Superconductors M2S-HTSC IV Grenoble (France) July 5-9 (1994) Physica C 235-240, 269-272 (1994)

VII. PHOTOEMISSION EVIDENCE FOR STRIPES

 " … Photoemission evidence for stripes…"
N. L. Saini, J. Avila, A. Bianconi, A. Lanzara, M. C. Asenzio, S. Tajima, G. D. Gu, N. Koshizuka Phys. Rev. Lett. 79, 3467-3470 (1997); Phys. Rev. Lett. 82, 2619 (1999).

excerpt from R.S. Markiewicz Dispersion of ordered stripes Phases in the cuprates cond-mat{9911108 - 8Nov 1999 (Pag. 1see more by this: in Topology of the Pseudogap and Shaddow Bands in Bi2Sr2CaCu2O8+d at Optimum Doping N.L. Saini, J. Avila, A. Bianconi, A. Lanzara, M.C. Asenzio, S. Tajima, G.D. Gu, N. Koshizuka Phys. Rev. Lett. 79, 3467-3470 (1997)
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see more by this:in Evidence for a striped phase of high Tc superconductor at the Fermi surface N.L. Saini, J. Avila, M.C. Asensio, S. Tajima, G.D. Gu, N. Koshizuka, A. Valletta, A. Lanzara, A. Bianconi Z. Phys. B 104, 703-706 (1997)

"Recently Saini et al [9] identified a set of electronic states crossing the Fermi level not far from the G point. They observed these states only in the G((0,0)->M1(p,0) direction and related these set of states to the existence of one-dimensional stripes due to charge and spin-ordering in the CuO2 plane."

excerpt from R.S. Markiewicz Dispersion of ordered stripes Phases

see more by this:in (9)

VIII. THE MINIGAPS DUE TO THE ORDERED STRIPES GIVE THE PSEUDOGAP PHENOMENOLOGY

 "While the CuO₂ metallic plane of Bi₂Sr₂CaCu₂O₈ (Bi2212) is often considered to be homogeneous, polarized Cu K-edge EXAFS studies find evidence for two different Cu-O(apical) distances (Bianconi 1994). This difference has been interpreted in terms of microscopic striped LTT and LTO domains. In the LTT-like domains, Bianconi (1994) has argued that the local distortion of the Cu-O octahedra leads to a trapping of the doped holes. Thus this work suggests that localized as well as itinerant holes exist in the CuO₂ planes of Bi2212.
…. Thus while we do not have a specific theory for the spin gap behavior of the under doped cuprates, we believe that there are both experimental and theoretical reasons to consider the possibility that this phenomenon is associated with local structure in the individual CuO₂ planes which differs from the average crystallographic structure."
Bianconi (1994): A. Bianconi Sol. State Commun. 89, 933 (1994)

 Excerpt from " Local microstructure and the cuprate spin gap puzzle"
by P. C. Hammel and D.J. Scalapino Phil. Mag. B 74, 523-528 (1996)
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"this provides a new interpretation for the pseudogap: stripe-induced Van Hove splitting" "the idea that the pseudogap is associated stripe minigaps has been proposed previously (pag. 14)
A. Bianconi, A. Valletta, A. Perali, and N. L. Saini Physica C 296, 269-280 (1998).

 excerpt from Dispersion of ordered stripes Phases in the cuprates by R.S. Markiewicz cond-mat 9911108, 8Nov 1999

see more by this: in: A. Bianconi, N. L. Saini, T. Rossetti, A. Lanzara, A. Perali, M. Missori, H. Oyanagi, H. Yamaguchi, Y. Nishihara and D. H. Ha, Phys. Rev. B 54, 12018 (1996).