arXiv subjects

M. Matusiak

Publications and source records attributed to M. Matusiak.

25 records · Page 2Linked to original sources

arXiv2009

Influence of the pseudogap on the Nernst coefficient of Y0.9Ca0.1Ba2Cu3Oy

We have studied the Nernst coefficient, v(T), of epitaxial thin films of the superconductor Y1-xCaxBa2Cu3Oy with x =0.05 and x = 0.1. The x = 0.1 sample has been measured at three different values of y, in the over- (OV), optimally- (OP), and under-doped (UD) states. As the doping level is reduced, v(T) starts to fall linearly with T at the temperature (T*) where we expect to see the influence of the pseudogap. The onset temperature of the superconducting fluctuation contribution to v(T) was found to vary slowly with the hole concentration (p) between p = 0.118 and 0.197. For the OP and UD samples, v(T>T*) is unusually large, being comparable with |S tan(Theta)| where S is the Seebeck coefficient and Theta the Hall angle.

cond-mat.supr-con↗

arXiv2008

Nernst effect of epitaxial YBCO films doped with Ca and Zn

We report Nernst effect measurements for some crystalline films of Ca and Zn-doped yttrium barium copper oxide grown by pulsed laser deposition. We argue that our results and most of the published data for LSCO are consistent with the theory of Gaussian superconducting fluctuations.

cond-mat.supr-con↗

arXiv2005

Electronic heat transport in the optimally doped superconductor YBa2Cu3O6.95: preservation of the Wiedemann-Franz law

Measurements of longitudinal and transverse transport coefficients were performed in the normal state of a high-quality single crystal of optimally-doped superconductor YBa2Cu3O6.95. We found the Hall-Lorenz number (Lxy) depends only weakly on temperature, thus no appreciable violation of the Wiedemann-Franz law has been observed. However, Lxy is about two times larger than the Sommerfeld's value of the Lorenz number. Our results can be interpreted consistently if we assume that the electronic system of YBa2Cu3O6.95 behaves like a Fermi-liquid with a pseudo-gap that opens at the Fermi level.

cond-mat.supr-con↗

arXiv2005

The Lorenz number in the optimally doped and underdoped Eu-123 superconductor

The temperature dependences of the Hall-Lorenz numbers (Lxy) in a EuBa2Cu3Oy (Eu-123) single crystal before and after oxygen reduction are reported. The study is based on data on the normal state longitudinal and transversal transport coefficients. Namely, the temperature dependences of the electrical resistivity, Hall coefficient, longitudinal thermal conductivity, and transverse thermal conductivity are presented. The set of measurements was performed for an optimally doped sample (y = 7), then the oxygen content in the the same crystal was reduced to y = 6.65, and the measurements were repeated. For both cases Lxy's are about two times larger than the Sommerfeld's value of the Lorenz number and depend weakly on temperature in a range 300 - 160 K. Below T = 160 K the Hall-Lorenz number for the optimally doped sample slowly drops, while the value of Lxy for the oxygen reduced sample begins to rise. Such results suggest that the electronic system in the investigated compound may be considered as a metallic one with pseudo-gaps that open at the Fermi level.

cond-mat.supr-con↗

arXiv2003

On the effect of heterovalent substitutions in ruthenocuprates

We discuss the properties of superconducting derivatives of the RuSr2GdCu2O8 (1212-type) ruthenocuprate, for which heterovalent doping has been achieved through partial substitution of Cu ions into the RuO2 planes (Ru1-xSr2GdCu2+xO8-d, 0 Ru doping achieved in these phases is found to decrease the temperature for magnetic ordering as well the volume fraction of the magnetic phase.

cond-mat.supr-con↗

arXiv2002

Magnetism and superconductivity in Ru(1-x)Sr2RECu(2+x)O(8-d) (RE=Gd, Eu) and RuSr2Gd(1-y)Ce(y)Cu2O8 compounds

We discuss the properties of new superconducting compositions of Ru(1-x)Sr2RECu(2+x)O(8-d) (RE=Gd, Eu) ruthenocuprates that were synthesized at 600 atm. of oxygen at 1080 C. By changing ratio between the Ru and Cu, the temperature of superconducting transition (Tc) raises up to Tc max=72 K for x=0.3, 0.4. The hole doping achieved along the series increases with Cu->Ru substitution. For x different than x=0, Tc can be subsequently tuned between Tc max and 0 K by changing oxygen content in the compounds. The magnetic characteristics of the RE=Gd and Eu based compounds are interpreted as indicative of constrained dimensionality of the superconducting phase. Muon spin rotation experiments reveal the presence of the magnetic transitions at low temperatures (Tm=14-2 K for x=0.1-0.4) that can originate in the response of Ru/Cu sublattices. RuSr2Gd(1-y)Ce(1-y)Cu2O8 (0 Gd substitution. Properties of these two series allow us to propose phase diagram for 1212-type ruthenocuprates that links their properties to the hole doping achieved in the systems. Non-superconducting single-phase RuSr2GdCu2O8 and RuSr2EuCu2O8 are reported and discussed in the context of the properties of substituted compounds.

cond-mat.supr-con↗

arXiv1999

Normal State Ettingshausen Effect in La_{2-x}Sr_{x}CuO_{4}

A method for measurements of small (metallic) Ettingshausen coefficient (P) was developed. The influence of the dominating thermal effects, the Joule and Thomson heats, was eliminated making use of the odd symmetry of the Ettingshausen temperature gradient in respect with reversing of the direction of the magnetic field and electrical current. The method was applied to La_{2-x}Sr_{x}CuO_{4} ($x=0.03÷0.35$) high-T_c superconductor in normal state. We have found that in the whole composition range the Ettingshausen coefficient is of the order of 10^{-7} m^{3} K/J which is characteristic of typical metals. The coefficient changes sign from positive to negative near $x\approx 0.07$. Weak variation of P is in contrast to the behavior of other transport coefficients for La_{2-x}Sr_{x}CuO_{4}, as the thermoeletric power or the Hall coefficient, which have been reported in literature to change their values by more than two orders of magnitude with Sr doping.

cond-mat.supr-con↗