A study of the 15K superconducting transition in La2CuO4+δ

Hor, P. H.; Li, Zugang

doi:10.1016/s0921-4534(00)01432-5

Cited by 2 publications

(2 citation statements)

References 2 publications

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“…It seems that the 10 K phase observed in our samples resembles the 15 K phase reported by many authors. However, as reported before [19,20], the 15 K phase occurs in heavily doped samples and is always accompanied by other phases with high T C 's, such as 32 K or 42 K. According to refs. [21,22], when the average carrier concentration p is 0.125 (δ ∼ 0.0625), the system would separate into a p = 1/8 phase with suppressed T C of 15 K, and a phase with high T C equal to 32 K. Our samples were sintered at ambient atmosphere, thus we cannot regard them as in the case of heavily doped samples.…”

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confidence: 58%

Enhancement of Josephson coupling in La₂CuO_{4 + δ}by doping of CuO vapor during sintering

2003

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The transport properties of La2CuO 4+δ prepared under ambient atmosphere, using CuO vapor as doping resource, have been investigated in this paper. Two distinct transition temperatures were found from the doped sample. The high-temperature one, occurring at about 35 K, comes from the known 32 K phase. The other one appearing near 10 K is regarded as the result of Josephson coupling. Compared to the doped sample, the undoped sample shows weak Josephson coupling. We argue that the enhancement of Josephson coupling results from denser and more compacted grain boundaries in the doped sample, while the undoped sample has larger fractions of pores, which are harmful to this coupling. An interesting phenomenon is also observed: when Josephson coupling disappears due to an applied magnetic field or time elapse, the resistance increases as a power law, T −1/2 , in the low-temperature region.

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confidence: 58%

Enhancement of Josephson coupling in La₂CuO_{4 + δ}by doping of CuO vapor during sintering

2003

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“…At δ = 0.082 (corresponding to the hole concentration n h = 0.125 = 1/8) the superconducting volume fraction of the 30 K phase is greatly diminished but that of the 15 K phase is not changed. 28 This results in a fast drop of the onset-T c for superconductivity from about 30 K to 15 K at this special hole concentration in analogy to the so called 1/8 anomaly in the La 2−x (Sr, Ba) x CuO 4 -system.…”

Section: A Ambient Pressure Resultsmentioning

confidence: 87%

Intrinsic tendency of electronic phase separation into two superconducting states inLa2−xSrx
Lorenz
¹
,
Li
²
,
Honma
³

et al. 2002
Phys. Rev. B
33
6
29
0
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The effect of hydrostatic pressure up to 2 GPa on the superconductiong transitions in La 2−x Sr x CuO 4+δ is investigated. The ambient and high pressure properties of two series of samples with x=0 and x=0.015 and 0< δ <0.1 are characterized and compared by ac-susceptibility measurements. At ambient pressure both sets of samples fit into the same phase diagram as a function of the total hole concentration, n h . For n h < 0.085 there is a single superconducting transition (T c ≈ 30K) with an unusually large pressure coefficient, dT (30) c /dp ≈ 10 K/GP a. At higher hole density (n h > 0.085) a second superconducting transition (T c ≈ 15K) follows the first transition upon cooling and the pressure shift of this transition is negative, dTAt the boundary as the hole density is close to 0.085 the phase separation can be induced by pressure. The results are explained in terms of a strong correlation of the interstitial oxygen with the hole system in the CuO-planes.Pressure, applied at ambient temperature, causes a redistribution of holes.The mobile oxygen dopants follow and enhance T c as well as the tendency to phase 1 separation. If pressure is changed at low temperature (< 100K) the effects on T c and phase separations are greatly diminished because the interstitial oxygen becomes immobile at low T. Our results indicate that the dopant effects are important. Dopants and holes should be treated as a single globally correlated state. When thermodynamic euqilibrium is approached in the oxygen-doped samples, we find that there is an intrinsic tendency of electronic phase separation of doped holes into two distinct superconducting states.

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A study of the 15K superconducting transition in La2CuO4+δ

Cited by 2 publications

References 2 publications

Enhancement of Josephson coupling in La₂CuO_{4 + δ}by doping of CuO vapor during sintering

Enhancement of Josephson coupling in La₂CuO_{4 + δ}by doping of CuO vapor during sintering

Intrinsic tendency of electronic phase separation into two superconducting states inLa2−xSrx
Lorenz
¹
,
Li
²
,
Honma
³

et al. 2002
Phys. Rev. B
33
6
29
0
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A study of the 15K superconducting transition in La2CuO4+δ

Cited by 2 publications

References 2 publications

Enhancement of Josephson coupling in La2CuO4 + δby doping of CuO vapor during sintering

Enhancement of Josephson coupling in La2CuO4 + δby doping of CuO vapor during sintering

Intrinsic tendency of electronic phase separation into two superconducting states inLa2−xSrxLorenz1, Li2, Honma3 et al. 2002Phys. Rev. B336290View full textAdd to dashboardCite

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Enhancement of Josephson coupling in La₂CuO_{4 + δ}by doping of CuO vapor during sintering

Enhancement of Josephson coupling in La₂CuO_{4 + δ}by doping of CuO vapor during sintering

Intrinsic tendency of electronic phase separation into two superconducting states inLa2−xSrx
Lorenz
¹
,
Li
²
,
Honma
³

et al. 2002
Phys. Rev. B
33
6
29
0
View full text Add to dashboard Cite