Growth conditions, structure, and superconductivity of pure and metal-doped FeTe1-xSex single crystals

TL;DR

This study investigates how growth conditions, doping, and structural quality affect superconductivity in FeTe1-xSex crystals, revealing that certain dopants and disorder suppress superconductivity likely due to magnetic scattering effects.

Contribution

It provides new insights into the effects of various metal dopants and structural disorder on the superconducting properties of FeTe1-xSex crystals.

Findings

Only Co, Ni, and Cu substitute Fe ions in the crystal structure.

Disorder from non-substituting ions suppresses superconductivity.

Magnetic and nonmagnetic doping affects Tc and superconductivity stability.

Abstract

Superconducting single crystals of pure FeTe1 xSex and FeTe0.65Se0.35 doped with Co, Ni, Cu, Mn, Zn, Mo, Cd, In, Pb, Hg, V, Ga, Mg, Al, Ti, Cr, Sr or Nd into Fe ions site have been grown applying Bridgman's method. It has been found that the sharpness of transition to the superconducting state in FeTe1 xSex is evidently inversely correlated with crystallographic quality of the crystals. Among all of the studied dopants only Co, Ni and Cu substitute Fe ions in FeTe0.65Se0.35 crystals. The remaining examined ions do not incorporate into the crystal structure. Nevertheless, they form inclusions together with selenium, tellurium and/or iron, what changes the chemical composition of host matrix and therefore influences Tc value. Small disorder introduced into magnetic sublattice, by partial replacement of Fe ions by slight amount of nonmagnetic ions of Cu (~ 1.5 at%) or by magnetic ions of Ni (~ 2 at%) and Co (~5 at%) with spin value different than that of Fe ion, completely suppresses superconductivity in FeTe1 xSex system. This indicates that even if superconductivity is observed in the system containing magnetic ions it can not survive when the disorder in magnetic ions sublattice is introduced, most likely because of magnetic scattering of Cooper pairs.