Observation of two distinctdxz/dyzband splittings in FeSe

Abstract

We report the temperature evolution of the detailed electronic band structure in FeSe singlecrystals measured by angle-resolved photoemission spectroscopy (ARPES), including the degeneracy removal of the dxz and dyz orbitals at the Γ/Z and M points, and the orbital-selective hybridization between the dxy and d xz/yz orbitals. The temperature dependences of the splittings at the Γ/Z and M points are different, indicating that they are controlled by different order parameters. The splitting at the M point is closely related to the structural transition and is attributed to orbital ordering defined on Fe-Fe bonds with a d-wave form in the reciprocal space that breaks the rotational symmetry. In contrast, the band splitting at the Γ/Z points remains at temperature far above the structural transition. Although the origin of this latter splitting remains unclear, our experimental results exclude the previously proposed ferro-orbital ordering scenario.

Unveiling the hidden nematicity and spin subsystem in FeSe

“…x , the fit of A 1,90 leads to a gap amplitude 2Δ(0) = 8.14k B T s = 56 meV, consistent with the energy splitting between d yz and d xz near the M point in the Brillouin zone revealed from ARPES; 27,28 details of the fitting and discussions are available in section S3 of Supplementary Information. Furthermore, the temperature dependence of Δ (T) is totally consistent with that of the splitting energy at the M point as shown by the solid stars in Fig.…”

“…1a) in this phase, as also indicated in other experiments. 10,[14][15][16][26][27][28] We show below that this nematicity in dynamics reveals information of both the quasiparticle and magnetic channels. Astonishingly, ΔR/R shows profound nematic fluctuations even at T = 150 K, far above T s (Fig.…”

“…The orbital polarization at the Γ point is related to the band splitting that exists above T s and was observed by ARPES. 28 The origin of the band splitting at the Γ point remains elusive, 28 but is unlikely due to nematic fluctuations for T > T s since regular ARPES probes static orders.) Overall, we have observed both nematic and magnetic fluctuations in FeSe at high temperatures.…”

Effect of impurity substitution on band structure and mass renormalization of the correlatedFeTe0.5Se0.5superconductor

“…We could resolve three hole pockets near the zone center and an electron pocket near the zone corner in the case of FeTe 0.5 Se 0.5 , consistent with the band structure of the similar compounds [38][39][40][41][42][43], whereas only two hole pockets are resolved near the center and an electron pocket is resolved near the corner of the Brillouin zone in the case of Fe 0.9 Ni 0.1 Te 0.5 Se 0.5 , suggesting that the hole pocket that has predominantly xy orbital character is very sensitive to impurity scattering. We observe a decrease in the size of the hole pockets and an increase in the size of the electron pockets with Ni substitution, suggesting an effective electron doping.…”

Effects of strain on the electronic structure, superconductivity, and nematicity in FeSe studied by angle-resolved photoemission spectroscopy

“…Another holelike band (α) with the top of dispersion below the Fermi level (E F ) is also recognized. These bands persist in the nematic phase, keeping their energy positions nearly stationary to temperature [10][11][12][13]. On the other hand, the band structure around the M point is significantly reconstructed by nematicity.…”