Stripes in oxygen-enriched cuprates

Abstract

Charge-order stripes of different types occur when copper oxides are doped with either heterovalent metal, like La 2−x Sr x CuO 4 , or oxygen doped, like Y Ba 2 Cu 3 O 6+y . The difference shows up in the doping dependence of their incommensurability: q c (x) ∝ √ x − p but q c (y) ≈ 0.3. The square-root dependence in the former compound family results from Coulomb repulsion between doped holes (or electrons), residing pairwise in lattice-site O (or Cu) atoms of the CuO 2 planes.The almost constant q c (y) value in the second family results from the aggregation of ozone-like molecules, formed from O 2− ions of the host with embedded oxygen atoms, O, at interstitial sites in the CuO 2 planes. The magnetic moments, m(O), of the lattice-defect O atoms in the first family arrange antiferromagnetically, which gives rise to accompanying magnetization stripes of incommensurability q m (x) = 1 2 q c (x). The ozone complexes have a vanishing magnetic moment, m = 0, which explains the absence of accompanying magnetization stripes in the second family.Embedding excess oxygen as O atoms in CuO 2 planes is likewise assumed for HgBa 2 CuO 4+δ and oxygen-enriched bismuth cuprates. A combination of characteristics from both families is present in oxygen-enriched La 2 CuO 4+y . The validity of determining the hole density in oxygen-enriched cuprates with the universal-dome method is independently confirmed. Besides causing different types of stripes, the two types of lattice-defect oxygen may also cause different types of superconductivity. This could explain the much higher T c,max in oxygen-enriched than Ae-doped cuprates, as well as the cusped cooling-curves of X-ray intensity diffracted by stripes in the former family.

Determination of doped charge density in superconducting cuprates from NMR or stripes

“…[3][4][5] The doped-hole density p (and doped-electron density n) of high-T c cuprates can also be determined from the incommensurability of charge-order and magnetization stripes, as shown in two recent papers. 6,7 Shedding new light on the NQR results, here we point out commonalities with the stripe analysis, but also aspects that have been overlooked in the earlier studies or went unexplained.…”

“…(The slight decrease of q c (y) with increasing O-doping y is caused by secondary effects. 7 ) The distinctly different doping dependence of charge-order incommensurability disproves the common misconception that doped oxygen ionizes in Y Ba 2 Cu 3 O 6+y as O y → O 2− +2e + and separates-with O 2− entering the so-called charge-reservoir layer (that is, all planes except CuO 2 ) and the holes, 2e + , entering the CuO 2 planes. If this were true, then a rising square-root doping dependence of charge-order stripes in Y Ba 2 Cu 3 O 6+y would result, contrary to the observed q c (y) ≈ const.…”

“…1 shows, a large host of data from neutron scattering, hard X-ray diffraction, and resonant soft X-ray scattering is well described by Eq. (7). For low temperatures and low doping (x < 0.09), the offset value p in Eq.…”

“…and the onset density δ(y ons c ) = 0.035 hold for the whole family of oxygen-doped/enriched cuprates. 7 Figure 3 shows the observed incommensurabilties of charge-order stripes (q a c and q b c ), in Y Ba 2 Cu 3 O 6+y (and q a m of magnetization stripes if the crystals are not sufficiently annealed-not discussed here). For comparison, the (re-scaled) result from Fig.…”

Atomic configuration in cuprates at the closing of the pseudogap

“…As the ozone complex has no magnetic moment, m( Ö O Ö) = 0, magnetization stripes are absent in those compounds. 2 To summarize, there are commonalities and differences between the Ae-doped lanthanum cuprates from the first family and the oxygenated compounds from the second. What they have in common are neutral oxygen atoms in the CuO 2 planes.…”