Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1016/j.physc.2007.04.079

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Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：American Physical Society (APS)  

We study superconducting transition temperature (T-c) of oxygen-doped double-layer high-temperature superconductors YBa2Cu3O6+delta (0 <=delta <= 1) as a function of the oxygen dopant concentration (delta) and planar hole-doping concentration (P-pl). We find that T-c, while clearly influenced by the development of the chain ordering as seen in the T-c vs delta plot, lies on a universal curve originating at the critical hole concentration (P-c)=1/16 in the T-c vs P-pl plot. Our analysis suggests that the universal behavior of T-c(P-pl) can be understood in terms of the competition and collaboration of chemical phases and electronic phases that exist in the system. We conclude that the global superconductivity behavior of YBa2Cu3O6+delta as a function of doping is electronically driven and dictated by pristine electronic phases at magic doping numbers that follow the hierarchical order based on P-c, such as 2xP(c), 3xP(c), and 4xP(c). We find that there are at least two intrinsic electronic superconducting phases of T-c=60 K at 2xP(c)=1/8 and T-c=90 K at 3xP(c)=3/16.

DOI： 10.1103/physrevb.75.012508

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Other Link： http://harvest.aps.org/v2/journals/articles/10.1103/PhysRevB.75.012508/fulltext

Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：IOP Publishing  

We argue that in cuprate physics there are two types, hole content per CuO2 plane ( P-p1) and the corresponding hole content per unit volume ( P-3D), of hole-doping concentrations for addressing physical properties that are two dimensional ( 2D) and three dimensional ( 3D) in nature, respectively. We find that the superconducting transition temperature ( T-c) varies systematically with P-3D as a superconducting 'dome' with a universal optimal hole-doping concentration of P opt 3D = 1.6 x 10(21) cm(-3) for single-layer high-temperature superconductors. We suggest that P opt 3D determines the upper bound of the electronic energy of underdoped single-layer high-T-c cuprates

DOI： 10.1088/0953-2048/19/9/004

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Authorship：Lead author,　Corresponding author   Publishing type：Research paper (scientific journal)   Publisher：American Physical Society (APS)  

We have measured thermoelectric power (TEP) as a function of hole concentration per CuO2 layer P-pl in Y1-xCaxBa2Cu3O6 (P-pl=x/2) with no oxygen in the Cu-O chain layer. The room-temperature TEP as a function of P-pl, S-290(P-pl), of Y1-xCaxBa2Cu3O6 behaves identically to that of La2-zSrzCuO4 (P-pl=z). We argue that S-290(P-pl) represents a measure of the intrinsic equilibrium electronic states of doped holes and, therefore, can be used as a common scale for the carrier concentrations of layered cuprates. We shows that the P-pl determined by this new universal scale is consistent with both hole concentration microscopically determined by NQR and the hole concentration macroscopically determined by the formal valency of Cu. We find two characteristic scaling temperatures, T-S(*) and T-S2(*), in the TEP versus temperature curves that change systematically with doping. Based on the universal scale, we uncover a universal phase diagram in which almost all the experimentally determined pseudogap temperatures as a function of P-pl fall on two common curves; lower pseudogap temperature defined by the T-S(*) versus P-pl curve and upper pseudogap temperature defined by the T-S2(*) versus P-pl curve. We find that while pseudogaps are intrinsic properties of doped holes of a single CuO2 layer for all high-T-c cuprates, T-c depends on the number of layers, therefore, the inter layer coupling, in each individual system.

DOI： 10.1103/physrevb.70.214517

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Other Link： http://harvest.aps.org/v2/journals/articles/10.1103/PhysRevB.70.214517/fulltext

Language：English   Publishing type：Research paper (scientific journal)  

DOI： 10.1103/PhysRevB.65.144522

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Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：American Physical Society (APS)  

The pressure effect on the Hall coefficient R-H has been studied in Ca and oxygen co-doped Y1-xCaxBa2Cu3O, systems. R-H is not altered by pressure in samples without a Cu-O chain, whereas samples with an oxygen-deficient chain are altered in response to pressure, thus demonstrating the contribution of the oxygen reordering effect. However, even in samples with full chain ordering. R-H changes at a rate of -8.3%/GPa. This suggests the contribution of internal strain due to the presence of a Cu-O chain structure. We independently estimated the effect of two factors, oxygen reordering and internal strain, on the pressure effect on R-H. The oxygen-content dependence of the pressure effect on R-H can be explained by competition between oxygen reordering and internal strain.

DOI： 10.1103/physrevb.63.212506

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Other Link： http://harvest.aps.org/v2/journals/articles/10.1103/PhysRevB.63.212506/fulltext

Authorship：Lead author,　Corresponding author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：Elsevier BV  

DOI： 10.1016/0921-4534(91)90715-b

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Language：English  

DOI： 10.1016/S0921-4534(02)02513-3

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Language：English   Publisher：AMERICAN PHYSICAL SOC  

The effect of hydrostatic pressure up to 2 GPa on the superconductiong transitions in La2-xSrxCuO4+delta is investigated. The ambient- and high-pressure properties of two series of samples with x=0 and 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≈30 K) with an unusually large pressure coefficient, dT(c)((30))/dpapproximate to10 K/GPa. At a higher hole density (n(h)>0.085) a second superconducting transition (T(c)approximate to15 K) follows the first transition upon cooling and the pressure shift of this transition is negative, dT(c)((15))/dpapproximate to-4 K/GPa. At 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 toward phase separation. If pressure is changed at low temperature (<100 K) 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.

DOI： 10.1103/PhysRevB.65.144522

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Language：English   Publisher：AMERICAN PHYSICAL SOC  

The effect of hydrostatic pressure up to 2 GPa on the superconductiong transitions in La2-xSrxCuO4+delta is investigated. The ambient- and high-pressure properties of two series of samples with x=0 and 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≈30 K) with an unusually large pressure coefficient, dT(c)((30))/dpapproximate to10 K/GPa. At a higher hole density (n(h)>0.085) a second superconducting transition (T(c)approximate to15 K) follows the first transition upon cooling and the pressure shift of this transition is negative, dT(c)((15))/dpapproximate to-4 K/GPa. At 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 toward phase separation. If pressure is changed at low temperature (<100 K) 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.

DOI： 10.1103/PhysRevB.65.144522

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DOI： 10.1016/S0921-4534(00)00572-4

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Language：English   Publisher：ELSEVIER SCIENCE BV  

In this report, Ca-doped Pr-123 compounds have been synthesized under high pressure and the highest T-c up to 115K is achieved in Pr0.5Ca0.5Ba2Cu3Oy According to the X-ray analysis and thermal-electric power data, the Ca-ions induced carriers and reduced occupation of Pr ion in Ba site. These two effects could be the reason for the occurrence of superconductivity with higher T-c. Also, magnetic susceptibility under high pressure has been carried out by ac mutual inductance measurements. It showed that T-c increased linearly with pressure at dT(c)/dP =-+0.10 K/kbar up to 20 kbar. The pressure effect could be explained by carrier increase due to the shorter distance between Ca ion and CuO2 plane.

DOI： 10.1016/S0921-4534(00)00504-9

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Language：English   Publisher：ELSEVIER SCIENCE BV  

Unusual pressure-induced broadening of superconducting transition was observed in La1.916Sr0.084CuO4 without excess oxygen by ac resistance measurement (acR) and mutual inductance measurement (acM). Above similar to 9kbar, a negative dT(c)/dP determined by acM and a positive dT(c)/dP determined by acR are observed, while below similar to 9 kbar, both dT(c)/dP are positive in sign and identical in magnitude. This suggests the occurrence of the intralayer charge redistribution induced by pressure.

DOI： 10.1016/S0921-4534(00)01396-4

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Language：English   Publisher：ELSEVIER SCIENCE BV  

In this report, Ca-doped Pr-123 compounds have been synthesized under high pressure and the highest T-c up to 115K is achieved in Pr0.5Ca0.5Ba2Cu3Oy According to the X-ray analysis and thermal-electric power data, the Ca-ions induced carriers and reduced occupation of Pr ion in Ba site. These two effects could be the reason for the occurrence of superconductivity with higher T-c. Also, magnetic susceptibility under high pressure has been carried out by ac mutual inductance measurements. It showed that T-c increased linearly with pressure at dT(c)/dP =-+0.10 K/kbar up to 20 kbar. The pressure effect could be explained by carrier increase due to the shorter distance between Ca ion and CuO2 plane.

DOI： 10.1016/S0921-4534(00)00504-9

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Language：English   Publisher：ELSEVIER SCIENCE BV  

Unusual pressure-induced broadening of superconducting transition was observed in La1.916Sr0.084CuO4 without excess oxygen by ac resistance measurement (acR) and mutual inductance measurement (acM). Above similar to 9kbar, a negative dT(c)/dP determined by acM and a positive dT(c)/dP determined by acR are observed, while below similar to 9 kbar, both dT(c)/dP are positive in sign and identical in magnitude. This suggests the occurrence of the intralayer charge redistribution induced by pressure.

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Pressure effect on Hall coefficient, RH has been investigated in Y1-xCaxBa2Cu3Oy system with and without Cu-O chain structure, which is known as a charge reservoir. In the samples with Cu-O chain (y≠6), it was found that RH changes by pressure. But, in the samples without Cu-O chain (y=6), it was found that RH does not change by pressure. It is concluded that a source of the pressure-induced mobile carrier is the Cu-O chain structure in Y1-xCaxBa2Cu3Oy system. [high-Tc superconductor, Hall coefficient, Cu-O chain structure, oxygen-content, lattice parameter]. © 1998, The Japan Society of High Pressure Science and Technology. All rights reserved.

DOI： 10.4131/jshpreview.7.580

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Pressure effect on Hall coefficient, RH has been investigated in Y1-xCaxBa2Cu3Oy system with and without Cu-O chain structure, which is known as a charge reservoir. In the samples with Cu-O chain (y≠6), it was found that RH changes by pressure. But, in the samples without Cu-O chain (y=6), it was found that RH does not change by pressure. It is concluded that a source of the pressure-induced mobile carrier is the Cu-O chain structure in Y1-xCaxBa2Cu3Oy system. [high-Tc superconductor, Hall coefficient, Cu-O chain structure, oxygen-content, lattice parameter]. © 1998, The Japan Society of High Pressure Science and Technology. All rights reserved.

DOI： 10.4131/jshpreview.7.580

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Language：English   Publisher：ELSEVIER SCIENCE BV  

Pressure effect on Hall coefficient, R-H was investigated in Y0.9Ca0.1Ba2Cu3Oy (6.72 less than or equal to y less than or equal to 6.98) samples with Cu-O chain structure and Y1-xCaxBa2Cu3Oy (y=6) samples without Cu-O chain structure. it is found that the Cu-O chain structure is a source of the pressure-induced mobile carrier.

DOI： 10.1016/S0921-4534(97)00415-2

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Language：English   Publisher：Elsevier  

Pressure effect on Hall coefficient, RH was investigated in Y0.9Ca0.1Ba2Cu3Oy (6.72≤y≤6.98) samples with Cu-O chain structure and Y1-xCaxBa2Cu3Oy (y=6) samples without Cu-O chain structure. It is found that the Cu-O chain structure is a source of the pressure-induced mobile carrier.

DOI： 10.1016/S0921-4534(97)00415-2

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Authorship：Lead author   Language：English  

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Language：English  

DOI： 10.1007/BF02562810

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Language：English   Publisher：ELSEVIER SCIENCE BV  

Hall coefficient R(H) and superconducting transition temperature T-c in Y0.9Ca0.1Ba2Cu3Oy with 6.59 less than or equal to y less than or equal to 7.01 have been measured under ambient pressure and under high pressure up to 2GPa. It is found that the relation of T-c and Hall number 1/eR(H) under high pressure is explained in terms of the change in the carrier density and the pressure-induced pairing effect which depends on the oxygen-content.

DOI： 10.1016/0921-4534(94)91953-4

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Language：English   Publisher：ELSEVIER SCIENCE BV  

Hall coefficient R(H) and superconducting transition temperature T-c in Y0.9Ca0.1Ba2Cu3Oy with 6.59 less than or equal to y less than or equal to 7.01 have been measured under ambient pressure and under high pressure up to 2GPa. It is found that the relation of T-c and Hall number 1/eR(H) under high pressure is explained in terms of the change in the carrier density and the pressure-induced pairing effect which depends on the oxygen-content.

DOI： 10.1016/0921-4534(94)91953-4

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Language：Japanese   Publisher：The Physical Society of Japan (JPS)  

CiNii Books

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Event date： 2007.9

Language：Japanese   Presentation type：Poster presentation  

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Event date： 2006.9

Language：Japanese   Presentation type：Poster presentation  

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Event date： 2006.6

Language：English   Presentation type：Oral presentation (general)  

Venue：Dresden (Germany)  

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Event date： 2004.4

Language：Japanese   Presentation type：Oral presentation (general)  

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Event date： 2003.5

Language：English   Presentation type：Poster presentation  

Venue：Rio de Janeiro (Brazil)  

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Event date： 2002.9

Language：Japanese   Presentation type：Poster presentation  

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Event date： 2002.8

Language：English   Presentation type：Poster presentation  

Venue：Hiroshima (Japan)  

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Event date： 2001.3

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：八王子市  

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Event date： 2000.2

Language：English   Presentation type：Poster presentation  

Venue：Houston (USA)  

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Event date： 2000.2

Language：English   Presentation type：Poster presentation  

Venue：Houston (USA)  

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Event date： 2000.2

Language：English   Presentation type：Poster presentation  

Venue：Houston (USA)  

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Event date： 1998.3

Language：Japanese   Presentation type：Poster presentation  

Venue：船橋市  

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Event date： 1997.10

Language：Japanese   Presentation type：Poster presentation  

Venue：神戸市  

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Event date： 1997.8

Language：English   Presentation type：Poster presentation  

Venue：京都市  

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Event date： 1997.2 - 1997.3

Language：English   Presentation type：Poster presentation  

Venue：Beijing (China)  

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Event date： 1996.10

Language：English   Presentation type：Poster presentation  

Venue：札幌市  

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Event date： 1996.8

Language：English   Presentation type：Poster presentation  

Venue：Prague (Czech)  

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Event date： 1995.9

Language：Japanese   Presentation type：Poster presentation  

Venue：堺市  

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Event date： 1994.7

Language：English   Presentation type：Poster presentation  

Venue：Grenoble (France)  

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Event date： 1994.7

Language：English   Presentation type：Poster presentation  

Venue：Grenoble (France)  

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Event date： 1993.3

Language：Japanese   Presentation type：Oral presentation (general)  

Venue：仙台市  

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