Cu-site-substitution effects on the 1/8 anomaly in the high-Tc cuprates and on the anomaly at x=0.21 in La2−xSrxCuO4

Distinctive Features of Metal-Insulator Transitions, Multiscale Phase Separation, and Related Effects in Hole-Doped Cuprates

“…Thus, we see that, in LSCO, the metal-insulator transitions and multiscale (from nanoscale to macroscale) phase separation into carrier-rich metallic (at > 1 and > 2 ) regions and carrier-poor insulating (at < 2 and < 1 ) regions may occur in the doping interval from ≃ 0.042 (lightly doped region) to 0.131 (underdoped region including also the "magic doping = 1/8"), while such metalinsulator transitions and phase separation in YBCO would occur in the doping interval from ≃ 0.021 to ≃ 0.125. These results are in reasonable agreement with the experimental data on the metal-to-insulator crossover and the stripe formation in lightly doped and underdoped cuprates [18,24,25,61,62].…”

“…Thus, one can expect the coexistence of insulating and metallic/superconducting phases in lightly to optimally doped cuprates and the suppression of superconductivity (i.e., c ) in underdoped cuprates near the = 1/8 doping due to an increase of the insulating volume fraction at the expense of the superconducting volume fraction at < 0.13. Actually, in underdoped cuprates, the superconductivity is markedly suppressed, when the dynamic stripes become static at = 1/8 [25]. Finally, the insulating phases persist in the slightly underdoped cuprates in the form of narrow nanoscale stripes ( Fig.…”

“…Attempts to explain the unusual normal-state properties of underdoped cuprates (in particular, insulatormetal crossover taking place far in the superconducting region, the insulating behavior of the -axis resistivity, and the temperature-dependent magnetic susceptibility in the metallic state) and their suppressed superconductivity and pseudogap behaviors have led to many controversial assumptions (see, e.g., Refs. [1,4,19,24,25,28]). One point of view, which stands out in the context of the experimental evidence, is the idea of preformed pairs [6] considered to be the fluctuating Cooper pairs, which are believed to be present in HTSC well above c [63].…”

“…Ap-parently, the evolution of the insulating and metallic/superconducting phases in these materials are manifested in the temperature dependences of their magnetic susceptibility [22] and resistivity [23], as well as in the suppression of superconductivity (i.e. in the so-called 1/8 anomaly) in the underdoped regime [24,25]. Despite the considerable theoretical effort (see Refs.…”

Relationship Between Electronic and Crystal Structure in Nd 1 + x Ba 2 − x Cu 3 O 6 + δ

“…x Ba x CuO 4 [18] called "anomaly 1/8". The nature of the latter is known to be the correlated charge and spin ordering in electron-hole system of HTSC at the hole doping of 1/8 per Cu [19][20][21][22] that exerts a negative effect on the superconducting properties. On the other hand, coincidence of  at which the singularities on the T c () and a, c () curves are manifested can testify about common origin of the observed effects.…”