The Microscopic Mechanism of Superconductivity in FeSe

by Tommy on 27/01/2017

Behold the spectroscopic microscopic mechanism theory era of superconductivity.

https://arxiv.org/abs/1701.07813

Mechanism for nematic superconductivity in FeSe, Jian-Huang She, Michael J. Lawler and Eun-Ah Kim (26 January 2017)

Despite its seemingly simple composition and structure, the pairing mechanism of FeSe remains an open problem due to several striking phenomena. Among them are nematic order without magnetic order, nodeless gap and unusual inelastic neutron spectra with a broad continuum, and gap anisotropy consistent with orbital selection of unknown origin. Here we propose a microscopic description of a nematic quantum paramagnet that reproduces key features of neutron spectra averaged over nematic domains. We then study how the spin fluctuations of the local moments lead to pairing within a spin-fermion model. We find the resulting superconducting order parameter to be nodeless s ± d-wave within each domain. Further we show that orbital selective Hund’s coupling can readily capture observed gap anisotropy. Our prediction for the inelastic neutron spectra within a single nematic domain calls for inelastic neutron scattering in a detwinned sample.

The microspectroscopic era.

See also: https://arxiv.org/abs/1701.07728

FeTe1−xSex monolayer films: towards the realization of high-temperature connate topological superconductivity, Xun Shi, Zhiqing Han, Pierre Richard, Xianxin Wu, Xiliang Peng, Tian Qian, Shancai Wang, Jiangping Hu, Yujie Sun and Hong Ding (26 January 2017)

We performed angle-resolved photoemission spectroscopy studies on a series of FeTe1−xSex monolayer films grown on SrTiO3. The superconductivity of the films is robust and rather insensitive to the variations of the band position and effective mass caused by the substitution of Se by Te. However, the band gap between the electron- and hole-like bands at the Brillouin zone center decreases towards band inversion and parity exchange, which drive the system to a nontrivial topological state predicted by theoretical calculations. Our results provide a clear experimental indication that the FeTe1−xSex monolayer materials are high-temperature connate topological superconductors in which band topology and superconductivity are integrated intrinsically.

Now extend that microscopic theory into this.

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