Quantum oscillations probe the normal electronic states of novel superconductors

Abstract

In 2008, new classes of high-temperature superconductors containing iron have been discovered. These iron pnictides offer a new area of exploration and understanding of superconductivity. Quantum oscillations is a bulk probe that allows us to map out the full Fermi surface of a superconducting system in its normal metallic state. These oscillations are determined by the Landau quantization in high magnetic fields and are usually observed at very low temperatures and in very clean samples. By knowing the exact nature of the quasi-particles in the normal state and the degree of electronic correlations, one can simplify and restrict theoretical models required to understand the pairing mechanism in superconductors. I will discuss the current understanding of the Fermi surface studies in iron-based superconductors as determined from quantum oscillations.

A common thread: The pairing interaction for unconventional superconductors

“…The main studies of the multiple-orbital models which have been carried out for the heavy-fermion and Fe-based materials have been based upon weak-coupling RPA (Kuroki et al, 2008Graser et al, 2009;Chubukov, 2012), FLEX (Ikeda, Arita, and Kuneš, 2010), or FRG methods (Platt, Honerkamp, and Hanke, 2009;Wang, Wan, and Wang, 2009;Zhai, Wang, and Lee, 2009;Uebelacker and Honerkamp, 2012). Just as the Monte Carlo calculations (Maier, Jarrell, and Scalapino, 2006b) of the four-point vertex allow one to study the interplay of the various spin, charge, and pairing correlations on an equal footing as the temperature is reduced (see, for example, Fig.…”

Spin resonance inAFe2Se2withs-wave pa

“…We recall that the hybridization in 122 compounds can be traced to the checkerboard arrangement of pnictogen/chalcogene atoms staggered above and below the iron planes, [57][58][59][60] . The iron lattice sites at iax+jaŷ +kcẑ, with integer i, j, k then belong to even and odd sublattices, defined by an even and odd i + j + k, respectively.…”

Gap structure in Fe-based superconductors with accidental nodes: The role of hybridization

“…In the presence of a spinorbit interaction λ k does not have zeros even in 1111 systems 13,14 . Because our goal is to understand the generic effect of the hybridization between the two bands, we will treat λ k as a constant λ 14,16 . Earlier analysis of the effect of λ k including its angular dependence (but without interplay with inter-pocket pairing) has shown that the results are qualitatively the same as for constant λ 10 .…”