Theoretical and experimental investigation of magnetotransport in iron chalcogenides

Abstract

We explore the electronic, transport and thermoelectric properties of Fe 1+y Se x Te 1−x compounds to clarify the mechanisms of superconductivity in Fe-based compounds. We carry out first-principles density functional theory (DFT) calculations of structural, electronic, magnetic and transport properties and measure resistivity, Hall resistance and Seebeck effect curves. All the transport properties exhibit signatures of the structural/magnetic transitions, such as discontinuities and sign changes of the Seebeck coefficient and of the Hall resistance. These features are reproduced by calculations provided that antiferromagnetic correlations are taken into account and experimental values of lattice constants are considered in DFT calculations. On the other hand, the temperature dependences of the transport properties can not be fully reproduced, and to improve the agreement between experiment and DFT calculations it is necessary to go beyond the constant relaxation time approximation and take into account correlation effects.

Magneto-Seebeck effect inRFeAsO(R=rareearth) compounds: Probing the magnon drag scenario

“…In the case of FeTe, considered as parent compounds of the "11" family, Seebeck curves present similar features as the other families such as the abrupt jump below T N and a local minimum at low temperature, as well as some peculiarities such as the flat temperature behavior above T N [8][9][10].…”

Competing collinear magnetic structures in superconducting FeSe by first-principles quantum Monte Carlo calculations

“…For example, the PBE band structure is in poor agreement with experiments which report a considerably narrower bandwidth [13,14]. Furthermore the FeSe lattice constants display an average error of ∼ 0.1 Å independently from the exchange correlation functional employed (see for instance Ref [15] and Tab I). Despite useful work using dynamical mean field theory [16][17][18][19][20][21] and GW [22][23][24] methods, there is a strong need for high quality calculations that can better describe the electronic and crystal structure of these materials.…”

Theoretical investigation of FeTe magnetic ordering under hydrostatic pressure

“…10 The a and b axis are no longer equivalent as in the tetragonal structure and the angle between a and c axis is no longer 90°but ranges from 88.35°and 88.2°for P ≤2GPa, in a suitable agreement with what is found experimentally (89.17°) and in line with other theoretical calculations. 7,12 The atoms internal coordinates vary (with respect to those in the tetragonal structure) in such a way that stripes with the same spin orientation become closer and stripes with opposite spin orientation become more distant.…”

“…5,8 The ground state of FeTe is experimentally found as double stripe antiferromagnetically ordered phase (AFMs2) 9 and theoretically confirmed. [10][11][12] The AFMs2 ordering consists into an AFM alternation of pairs of ferromagnetically ordered stripes of Fe-atoms, and can be seen as a spin-density wave (SDW) with a wave vector half of that corresponding to the usual stripe AFM ordering found in pnictides. This magnetic phase survives at low temperature with no sign of superconducting phase transition.…”