The position of the `one-eighth' anomaly within the high-temperature superconductivity problem: matters concerning stripes and domains, Jahn-Teller effect and negative-<b><i>U</i></b>behaviour

Wilson, J. A.

doi:10.1088/0953-8984/10/15/015

Cited by 16 publications

(52 citation statements)

References 84 publications

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“…The 70 meV or 570 cm -1 phonons singled out in the above paragraph are rather special ones for YBCO 7 / a [110,4,2]. Of these two dynamic micro-orderings it is the charge order which appropriately takes precedence, it persisting up to higher temperatures, to higher hole doping content, and to greater system covalence [111] remember even BSCCO displays charge stripes [80], while, by contrast, magnetic effects already are much diminished in YBCO [112] in comparison with LSCO [113].…”

Section: Brief Resumé Of the Chemical Negative-u Approach To Htscmentioning

confidence: 76%

“…[78, 79, 1d,f]. One similarly might point to the consequences of the development of ordering in system microstructure closely associated with the p = 1 / 8 count [4]. µSR [80], NMR [81] and NQR [82] experiments all reveal that in the vicinity of the latter carrier count there occurs a certain resurgence of unpaired magnetic moment formation at low temperature.…”

Section: Brief Resumé Of the Chemical Negative-u Approach To Htscmentioning

confidence: 99%

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Developments in the negative-Umodelling of the cuprate HTSC systems

Wilson

2001

J. Phys.: Condens. Matter

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This paper emphasizes once more the many strands which go into creating the unique and complex nature of the mixed-valent HTSC cuprates, above T c as below. Clearly it is not sensible to look in isolation to the lattice, magnetic or electronic aspects of the situation. Circumstances are too tightly coupled and interdependent. What one is in a position to do is to ascribe some preeminence in these matters. The line taken in this paper, as in its predecessors, is that charge constitutes the prime mover, but this taken within a chemical context, relating to bonding effects in the copper oxides and to a crucial shell-filling negative-U term of large magnitude. What dictates the uniqueness of copper in this is its particular position within the periodic table at the end of the 3dseries. This provides access to (i) three stable valencies, (ii) to the limited metallicity of tightbinding, mixed-valent YBa 2 Cu 3 O 7 , etc., (iii) to the p/d hybridized limitation of magnetic behaviour, and (iv) above all to the shell closure effects, with their dramatic energy adjustments of the relevant double-loading states when sited in high-valent local environment. This behaviour rests on the inhomogeneous electronic and structural conditions existing within these tight-binding mixed-valent systems. Normally such systems show strong positive-U behaviour and are magnetic. Here the shell-filling effects negate this U term to leave a net negative U eff of −3 eV per pair. That positions the bosonic electron pairs degenerate with E F . RVB spin coupling within the stripe phase geometry set up by the doped charge removes much spin-flip pair breaking, while the adopted 2D crystal structure with its saddle-point dominated F.S. provides the ideal k-space geometry from which to secure the negative-U driven pair formation. The Jahn-Teller effect associated with the d 9 electron count is crucial in upholding the two-subsystem nature of the HTSC materials.This paper looks at the support for this scenario that can be extracted from the recent work of Corson, Li, Mook, Valla, Norman, Varma, Gyorffy and many others. To the author it remains a mystery why other researchers have not examined the potential of this route for understanding the unique characteristics of the HTSC cuprates.3

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Section: Brief Resumé Of the Chemical Negative-u Approach To Htscmentioning

confidence: 76%

Section: Brief Resumé Of the Chemical Negative-u Approach To Htscmentioning

confidence: 99%

Developments in the negative-Umodelling of the cuprate HTSC systems

Wilson

2001

J. Phys.: Condens. Matter

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“…Such spin conformations now are displayed in fig.2 for the revised 45° orientation of 2-q domain walling advocated in [32]. It is my belief that these spin structures stand in It has to be emphasized here that the negative-U scenario developed in [22][23][24][25][26][27][28][29][30][31][32][33] is one of electron pairs not hole pairs, the former associated with the attainment within a local negative-U state coordination unit of the fully closed-shell p 6 d 10 condition, the 10 Cu III 2state.…”

Section: §1 Introduction and Background To Negative-u Interpretation mentioning

confidence: 87%

Two-gap, high temperature superconductor, ARPES data, the pseudogap, and magnetic circular dichroism from the negative-Uperspective

Wilson

2007

J. Phys.: Condens. Matter

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Recent photoemission work on underdoped HTSC cuprates between T c and T*, the pseudogap temperature, are interpreted within the framework of a previously developed twosubsystem, resonant negative-U scenario. From this exposition, incorporating a developed 2q diagonal striping model, detailed understanding follows of the ARPES results, together with certain STM and far infrared optical data. Identification of the origin of the magnetic circular dichroism and related effects exhibited by such materials below T* also appears to have been achieved.

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“…The issue of the above 'stripes' being one-dimensional (ID) or two-dimensional (2D) has been recently investigated by Wilson [11]. Based on new neutron scattering and t D ''' EXAFS data, Wilson shows for LBCO at x = 1/8, it is possible for the holes to be ordered in different ways, so the stripes could form with either one or two dimensions.…”

Section: Hole Concentrationmentioning

confidence: 99%