Transport properties of Bi-doped FeSe superconductor up to 700 K

Abstract

Polycrystalline samples of Fe1-xBixSe with x = 0.00, 0.02, 0.05, and 0.08 are prepared by conventional solid state reaction. The resistivity and thermopower are measured up to 700 K. The onset superconducting transition temperature decreases slightly with increasing Bi content. Transport behavior of electrical resistivity in the normal state is quite complex. A linear temperature dependence is found between 20 and 100 K. Above 150 K, the electrical resistivity behavior resembles misfit-layered cobalt oxides Ca3Co4O9+δ; a Fermi-liquid behavior of T2 dependence is observed between 150 and 210 K with the Fermi-liquid transport coefficient A having the size between 4.3 × 10−6 and 10 × 10−6 mΩ-cm/K2, followed by an incoherent metal and a high-temperature nonmetal-like behavior. Thermopower behavior is nonconventional. Sign crossover of thermopower occurs both below and above room temperature. According to the dynamical mean field calculations, the negative dip feature of thermopower between 110 and 130 K seems to be associated with excitations of a pseudogap ground state.

High Pinning Force Values of a Fe(Se, Te) Single Crystal Presenting a Second Magnetization Peak Phenomenon

“…Despite their low T c values, it has been demonstrated that the IBSs can be suitable for magnet and wire production and/or highpower applications and high-current transport thanks to their high values of critical current density J c , irreversibility field and upper critical field [11][12][13][14][15][16] as well as their good inter-grain connectivity [8,13,17,18]. Among the various IBS families, the 11 family has attracted a lot of interest due to its very simple crystalline structure and to the possibility of easily doping it with several elements of the periodic table [19][20][21][22][23] in order to improve the superconducting properties of the compounds. Among the compounds of the 11 family, Fe(Se, Te) is one of the most studied compounds in recent years due to its relatively high T c (for single crystals between 12 K and 14.5 K), its chemical stability and also because it does not present poisonous elements in its stoichiometry.…”

Fluctuating Cooper pairs in FeSe at temperatures exceeding double Tc

“…However, below ∼ 300 K, ρ(T ) transforms into roughly metallic-like dependence [3,12], and takes a shape resembling that observed for underdoped cuprate HTSCs (cuprates) [7,13] and FeAs-based superconductors (Fe-pnictides) [14,15]. Eventually, as T decreases, FeSe becomes superconducting (SC) with SC transition temperature T c ≈ 10 K at ambient pressure [1- 3,6,7], unexpectedly in a rather narrow range of Se concentration [16].…”

“…[6,7] and references therein), including the interplay between superconductivity and magnetism [8][9][10][11]. One such feature is the temperature dependence of the resistivity, ρ(T ), which turned out to be semiconductor-like in a wide temperature range above ∼ 350 K in single crystals [3] and above ∼ 315 K in polycrystalline materials [12].…”

High temperature thermoelectric properties of co-doped Ca3−xAgxCo3.95Fe0.05O9+δ (0≤x≤0.3)

“…Thermopower measurements were performed between 300 and 700 K using steady-state techniques with a temperature gradient of 0.5-1 K across the sample. A type E differential thermocouple was used to measure the temperature difference between hot and cold ends of the sample [17], which was measured using a Keithley 2000 multimeter. The thermopower of the sample was obtained by subtracting the thermopower of the Cu Seebeck probe.…”