Nematic electronic states under T_S and superconducting mechanism near nematic QCP in FeSe family

FeSe is an ideal platform to reveal the mechanism of nematiciy thanks to the rich reliable experimental data. Below T_S, (i) the hole-pocket becomes vertically ellipsoidal and the electron pocket around X point becomes horizontally ellipsoidal, due to the orbital polarization E_xz(k)-E_yz(k) with sign reversal [1]. In addition, recent ARPES experiments have revealed (ii) the electron pocket around Y point disappears below T_S. To explain the whole nematic Fermi surface structure in FeSe, we perform the self-consistent analysis of the the nematic electronic states below T_S. It is revealed that both (i) and (ii) are satisfactorily reproduced by the paramagnon interference processes [2]. In addition, enhancement of T_S aroung nematic QCP is naturally explained by the present scenario [2]. Thus, both the nematiciy and the superconductivity are uniquely explained based on the paramagnon interference mechanism.

[1] S. Onari and H. Kontani, Phys. Rev. Lett. 116, 227001 (2016).

[2] present authors, unpublished.