2 RESULTS HolePockets. In Fig.1we present detwinned ARPES spec-tra of the hole pocket of FeSe, using a photon energy of 23 eV which corresponds to the Z point at the top of the Brillouin

We present a systematic angle-resolved photoemission spectroscopy study of the superconducting gap in FeSe. The gap function is determined in a full Brillouin zone including all Fermi surfaces and kz-dependence. We find significant anisotropy of the superconducting gap in all momentum directions. While the in-plane anisotropy can be explained by both, nematicity-induced pairing anisotropy and

(e),(f) EDCs taken at the momentum pointed to by arrows in (b)–(d). All measurements are taken with 70 eV photons under odd polarization with respect to the cut direction. Although ARPES measurements indicated a the distinct pseudogap-like reduction in DOS in the hole pocket above $T_{\text{c}}$, 116) no discernible reduction in DOS was observed in STS measurements. 142) The evolutions of the BCS–BEC crossover behavior in FeSe $_{1-x}$ S x again suggest that a multiband system exhibits a unique feature that is absent in a single-band system.

2015-09-08 ARPES and inelastic neutron spectra measured on twinned and detwinned FeSe [15, 46, 66]. (a) ARPES spectra taken along the Γ - M direction on a twinned FeSe. (b,c) ARPES spectra taken on detwinned FeSe along the Γ - M X and Γ - M Y directions, respectively. (d,e) Energy distribution curves taken at the momentum pointed to by arrows in (a–c). We present a systematic angle-resolved photoemission spectroscopy study of the superconducting gap in FeSe.

We report results on epitaxial FeSe thin films grown by pulsed laser deposition (PLD) on CaF2 (001) substrates as obtained by exploiting the advantages of an all-in-situ ultra-high vacuum (UHV) laboratory allowing for direct high-resolution surface analysis by scanning tunnelling microscopy (STM), synchrotron radiation X-ray photoelectron spectroscopy (XPS) and angle-resolved photoemission spectroscopy … 2017-03-01 2017-05-05 2019-10-02 2017-06-09 Enabled by an angle-resolved photoemission spectroscopy beamline with a highly focused beam spot (nano-ARPES), we identify clear stripelike orthorhombic domains in FeSe with a length scale of 2012-07-03 We have revealed the existence of a novel electronic state in an highly unconventional multiband superconductor, FeSe, from the evolution of its electronic structure from the high-temperature tetragonal phase into the electronic nematic phase using angle resolved photoemission spectroscopy (ARPES). Bulk FeSe is an iron-based superconductor that has a maximum Tc of 8K. Surprisingly, the Tc of a single layer of FeSe film grown epitaxially on the SrTiO 3 substrate is enhanced to over 55K.

2020年6月8日 We measure the electronic structure of FeSe from within individual (nano- ARPES), we identify clear stripelike orthorhombic domains in FeSe

(b) ARPES spectra taken along the Γ−M direction on a twinned FeSe. (c),(d) ARPES spectra taken on detwinned FeSe along the Γ−M X and Γ−M Y directions, respectively. (e),(f) EDCs taken at the momentum pointed to by arrows in (b)–(d).

Here we present the influence of different STO surface terminations and photon energy dependent ARPES results which help to clarify the role of the substrate in the monolayer FeSe system. This work was supported by the U.S. Department of Energy, Office of Science, Basic Energy Sciences, Materials Sciences and Engineering Division under contract DE-AC02-76SF00515.

2021-02-17 High‐temperature superconductivity at the FeSe/SrTiO3 interface Yuan‐Yuan Xiang, Fa wang, DA Wang, Qiang‐Hua Wang, and Dong‐Hai Lee. Phys. Rev. B 86, 134508 (2012) Atomic and electronic structures of FeSe monolayer and bilayer thin films on SrTiO3(001): First‐principles study Kai … ARPES on Electronic Structure and Superconductivity of FeSe /SrTiO 3 Films Xingjiang ZHOU (周兴江) National Lab for Superconductivity Institute of Physics, Chinese Academy of Sciences, Beijing, China Strong Correlations and Unconventional Superconductivity: Towards a Conceptual Framework ， 2014/09/22--26, KITP, Santa Barbara spectroscopy (XPS) and angle-resolved photoemission spectroscopy (ARPES) on fresh surfaces. FeSe PLD growth protocols were ﬁne-tuned by optimizing target-to-substrate distance d and ablation frequency, atomically ﬂat terraces with unit-cell step heights are obtained, overcoming the spiral morphology often observed by others. the low temperature Fermi surface of FeSe as experimentally determined by ARPES consists of one ellipti-cal hole pocket and one orthogonally-oriented peanut-shaped electron pocket. ARPES Studies of Monolayer FeSe on MBE Controlled Titanate Heterostructures. For 2D films, interface interactions can play a critical role in determining the prevailing physics of the system. In the case of 1ML FeSe on SrTiO3, interfacial electron-phonon (e-ph) coupling greatly increases its superconducting Tc over its bulk counterpart.

(a) The ARPES map of the high-symmetry cut through top of the Brillouin zone for the tetragonal phase of FeSe 1 − x S x (x = 0, 0.18, 1) at 56–69 eV, together with a calculated slice for FeS in (b).
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While the full structure of the electron pockets consisting of two crossed ellipses may be observed in the tetragonal phase at temperatures above 90 2020-03-03 2018-06-05 2015-07-15 In this Nature paper, T. Shimojima (RIKEN CEMS) et al. use time-resolved ARPES to visualize the ultrafast dynamics of electronic nematicity in FeSe.

Nematic phase: the hole pocket distorts, one elongated electron pocket seen by ARPES.
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The first ARPES study on single-layer FeSe/STO films has provided key insights into the electronic origin of superconductivity in this system. A phase diagram

DFT calculation We report high resolution ARPES measurements of detwinned FeSe single crystals. The application of a mechanical strain is used to promote the volume fraction of one of the orthorhombic domains in the sample, which we estimate to be 80% detwinned. While the full structure of the electron pockets consisting of two crossed ellipses may be observed in the tetragonal phase at temperatures above 90 In this paper, to our knowledge, we report the first observation of an insulator–superconductor crossover in the iron-based superconductors by performing systematic angle-resolved photoemission (ARPES) measurements on the single-layer FeSe/SrTiO 3 films at various carrier concentrations. At a very low carrier concentration, the spectral The observation of replica bands in single-unit-cell FeSe on SrTiO3 (STO)(001) by angle-resolved photoemission spectroscopy (ARPES) has led to the conjecture that the coupling between FeSe Phase diagram of FeSe 1 − x S x and the suppression of electronic correlations by S substitution.

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For example, ARPES measurements of FeSe give an exclusive opportunity to investigate the electronic structure in nematic phase without magnetic order.

2020-01-31 2017-04-01 This quantitatively accurate model of FeSe is then used to predict a large temperature dependence of the chemical potential within this system, which we confirm via ARPES measurements. We then modify this tight binding model to account for the C4 symmetry breaking effect of the nematic phase of FeSe, which occurs below Ts = 90 K. ARPES on FeSe /SrTiO 3 Films and Silicene Xingjiang ZHOU (周兴江) National Lab for Superconductivity Institute of Physics, Chinese Academy of Sciences, Beijing, China 5th Swiss-China Workshop 2015/05/04-05, Brugg, Switzerland . Laser ARPES Group at the Institute of Physics, CAS, Beijing superconductors FeSe xTe1 x. Our ARPES data from the ternary iron chalcogenide FeSe0:42Te0:58 show a simple nonreconstructed Fermi surface (FS) that is well repro-duced by band structure calculations, which allows us to determine the mass enhancement for all Fermi surface sheets. In stark contrast to the moderately correlated 2019-12-03 ARPES: schematic Fermi surfaces of FeSe –3D Tetragonal phase: smaller pockets and band renormalisations. Nematic phase: the hole pocket distorts, one elongated electron pocket seen by ARPES.

2015-07-15

use time-resolved ARPES to visualize the ultrafast dynamics of electronic nematicity in FeSe. By probing detwinned crystals with different linear polarizations of their pulsed laser system (250 fs time resolution), they can selectively observe xz and yz orbital electrons. ARPES characterizations of 1UC FeSe/5UC LTO/STO films. a) Schematic diagram of the material structure. b) The Fermi surfaces of electron pockets near the zone corner M. Red lines indicate the Brillouin zone edges.

The application of a mechanical strain is used to promote the volume fraction of one of the orthorhombic domains in the sample, which we estimate to be 80$\%$ detwinned.