Photovoltaic effect in cuprate superconductor (Bi, Pb)2Sr2Ca2Cu3O10+δ and Bi2Sr2CaCu2O8+δ under magnetic field

The thermoelectric power S(T) studies of Bi2Sr2CaCu2O8 (Bi2212) samples, including as-processed Partially Melted (Bi2212-PM) and 800 °C O2-annealed (Bi2212-O2) are reported here. While Bi2212-PM sample is near optimum doping regime, Bi2212-O2 is an over-doped sample. T c S = 0 values obtained through S(T) data match very well with those deduced from the R(T). Interestingly, S(T) behavior of the optimally-doped Bi2212-PM sample is seen to be positive in whole temperature range, it is found negative for the over-doped Bi2212-O2 sample above T c S = 0 . The observed negative S(T) dependence of the over-doped Bi2212-O2 is in accord with the recent band structure calculations and is in line with the theoretical investigations on a van Hove singularity in electronic density of states in HTSc compounds.

Negative thermoelectric power of over-doped Bi2Sr2CaCu2O8 superconductor

Origin of photovoltaic effect in (Bi, Pb)2Sr2Ca2Cu3O10+δ /Ag heterostructure

An anomalous “dip” feature near the hole concentration of p ∼ 1/8 on the T
 c − p curve of Bi2Sr2 Ca1−x
 Dy
 x
 Cu2O8+δ
 (Dy-Bi2212) was reported. Dy-Bi2212 with p∼ 1/8 exhibited a “checkerboard charge order” with a wave vector ∼ 0.3 r.l.u., and well-defined coherent peaks were not observed in the quasiparticle tunneling spectra of this material, obtained from scanning tunneling microscopy/spectroscopy (STM/STS) experiments. The dip of the T
 c−p curve induced by the substitution of Dy in Bi2212 was similar to that observed in Zn-doped Bi2212 (Akoshima et al., Phys. Rev. B 57, 7491 1998), suggesting that the suppression of T
 c near p∼ 1/8 in Dy-Bi2212 is related to the pinning of the charge order.

1/8 Anomaly Induced by the Substitution of Dy in Underdoped Bi 2 Sr 2 Ca 1−x Dy x Cu 2 O 8+δ

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Experimental and Ab-initio studies of exotic superconductors

All the samples possess single-phase character and their superconducting transition temperatures (TcR=0) are 85, 90, and 72 K, respectively for Bi2212-MQ, Bi2212-N2, and Bi2212-O2. Though the Bi2212-MQ and Bi2212-N2 samples are in near optimum doping regime, the Bi2212-O2 is an overdoped sample. TcS=0 values obtained through S(T) data are also in line with those determined from the temperature dependence of resistance (TcR=0) and dc magnetization (Tcdia). Interestingly, S(T) behavior of the optimally doped Bi2212-MQ and Bi2212-N2 samples is seen to be positive in whole temperature range, the same is found negative for the overdoped Bi2212-O2 sample above TcS=0. This anomalous S(T) behavior is seen in the light of the recent band structure calculations and the ensuing split Fermi surface as determined by angle-resolved photoelectron spectroscopy.

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Anomalous thermoelectric power of overdoped Bi2Sr2CaCu2O8 superconductor

Temperature dependence of thermoelectric power S(T) of three differently processed Bi2Sr2CaCu2O8 (Bi2212) samples, viz. as-processed melt quenched (Bi2212-MQ), 6000C N2-annealed (Bi2212-N2) and 6000C O2-annealed (Bi2212-O2) is reported here. All the samples possess single-phase character and their superconducting transition temperatures (TcR=0) are 85 K, 90 K and 72 K respectively for Bi2212-MQ, Bi2212-N2 and Bi2212-O2. While Bi2212-MQ and Bi2212-N2 samples are in near optimum doping regime, Bi2212-O2 is an over-doped sample. TcS=0 values obtained through S(T) data are also in line with those deduced from the temperature dependence of resistance and DC magnetization. Interestingly, S(T) behaviour of the optimally-doped Bi2212-MQ and Bi2212-N2 samples is seen to be positive in whole temperature range, it is found negative for the over-doped Bi2212-O2 sample above TcS=0. These results have been seen in the light of the recent band structure calculations and the ensuing split Fermi surface as determined by angle-resolved photoelectron spectroscopy (ARPES).

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Jagdish Kumar Bains

Papers

Anomalous thermoelectric power of overdoped Bi2Sr2CaCu2O8 superconductor

Anomalous Thermoelectric power of over-doped Bi2Sr2CaCu2O8 superconductor

Negative thermoelectric power of over-doped Bi2Sr2CaCu2O8 superconductor