Mobility Analysis of FeTe Thin Films

Abstract

The Hall effect is investigated in detail for nonsuperconducting and superconducting FeTe thin films. The Hall coefficient commonly exhibits a sign reversal from positive in a hightemperature paramagnetic state to negative in a low-temperature antiferromagnetic state.Phenomenological analysis by a simple two-band Drude model indicates that hole mobility is significantly suppressed in the antiferromagnetic state. When suppression of the hole mobility is insufficient, superconductivity shows up in FeTe. This result strongly suggests that the itinerancy in both hole and electron channels is the essential factor for the occurrence of superconductivity in iron chalcogenide superconductors.KEYWORDS: iron chalcogenide, FeTe, Hall effect, thin films, two-band model Iron-pnictide 1) and iron-chalcogenide 2) superconductors are interesting materials when compared with cuprate superconductors. In both compounds, superconductivity is induced by chemical substitution to a parent antiferromagnet suggesting a possible common mechanism resulting in a similar phase diagram. However, the nature of the antiferromagnetic (AFM) state is qualitatively different. Cuprates are characterized as single-band metals and become an insulator, while iron-based superconductors are characterized as multi-band metals, [3][4][5] and exhibit metallic behavior even in the AFM state. 6) Actually undoped parent compounds of iron-based superconductors are compensated metals, where both electrons and holes contribute to the electrical transport. Therefore, this difference should be carefully considered when discussing the phase diagram, and it is important to understand how electrons and holes contribute to the electrical transport and superconductivity.The multi-band nature of iron-based superconductors has been predicted by several band calculations carried out for LaFeAsO, 3) BaFe 2 As 2 , 7) and Fe(Se,Te). 8) In LaFeAsO and BaFe 2 As 2 , superconductivity is induced by chemical substitution of elements with different *

Multiband effects and possible Dirac fermions inFe1+yTe0.6Se0.4Sun1, Taen2, Yamada3 et al. 2014Phys. Rev. B628481View full textAdd to dashboardCite

“…The µ MR reaches a value close to 800 cm 2 /Vs at 16 K comparable to the value (∼ 1000 cm 2 /Vs) obtained from quantum oscilla-tion in BaFe 2 As 2 . 51 The value of mobility obtained here is much larger than that reported in FeTe 1−x Se x thin films (< 10 cm 2 /Vs), 52 which again confirms the existence of Dirac fermions. µ MR decreases with increasing temperature since thermal fluctuation smear out the LL splitting.…”

Doping dependence of Hall coefficient and evolution of coherent electronic state in the normal state of the Fe-based superconductor Ba1−xKxFeOhgushi1, Kiuchi2 2012Phys. Rev. B

“…7,9,10,17 In contrast to an alloyed system, a rigid band shift of the Fermi level from a compensated metal with n h = n e = n 0 at x = 0 is reasonably anticipated in the current system. Then, the carrier density changes in form in which n h = n 0 + x m e m h +m e .…”

Effect of Vacuum Annealing on Superconductivity in Fe(Se,Te) Single Crystals

“…This would indicate that the suppression of superconductivity in Fe-rich crystals occurs mainly due to suppression of the itinerancy of electron-type carriers at low temperatures. 17,18) Since the interstitial iron makes the phase diagram of this FeSe-FeTe system complicated, researchers have tried to make the phase diagram with fewer excess iron, 19,20) but it is still unclear, for example, whether magnetism and superconductivity coexist or not, and therefore, excess Fe free phase diagram is highly desired.…”