The As-surface of an iron-based superconductor CaKFe4As4

Cao, Lu; Song, Yang; Liu, Ya-Bin; Zheng, Qi; Han, Guangyuan; Liu, Wenyao; Li, Meng; Chen, Hui; Xing, Yuqing; Cao, Guang‐Han; Ding, Hong; Lin, Xiao; Du, Shixuan; Zhang, Yuyang; Li, Geng; Wang, Ziqiang

doi:10.1007/s12274-021-3316-0

Cited by 8 publications

(14 citation statements)

References 44 publications

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“…This distance is √ 2 times the lattice constant. This observation is consistent with the previous STM results [30] and Fig. 4b represents As-terminated surface.…”

supporting

confidence: 94%

“…4b. This √ 2 × √ 2 structure is dominant on the cleaved surface [30]. This reconstruction expands the initial unit cell of a × a (left panel in Fig.…”

mentioning

confidence: 58%

“…4c. On the As-terminated surface, surface reconstruction occurs, resulting in the different height and different density of states on the two adjacent As atoms [30]. This renders half of the As atoms in the top…”

mentioning

confidence: 99%

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Common ($π$,$π$) Band Folding and Surface Reconstruction in FeAs-Based Superconductors

Cai,

Xie,

Yang

et al. 2021

Preprint

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High resolution angle-resolved photoemission spectroscopy (ARPES) measurements are carried out on CaKFe 4 As 4 , KCa 2 Fe 4 As 4 F 2 and (Ba 0.6 K 0.4 )Fe 2 As 2 superconductors. Clear evidence of band folding between the Brillouin zone center and corners with a (π,π) wave vector has been found from the measured Fermi surface and band structures in all the three kinds of superconductors. A dominant √ 2 × √ 2 surface reconstruction is observed on the cleaved surface of CaKFe 4 As 4 by scanning tunneling microscopy (STM) measurements. We propose that the commonly observed √ 2 × √ 2 reconstruction in the FeAs-based superconductors provides a general scenario to understand the origin of the (π,π) band folding. Our observations provide new insights in understanding the electronic structure and superconductivity mechanism in iron-based superconductors.

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“…This distance is √ 2 times the lattice constant. This observation is consistent with the previous STM results [30] and Fig. 4b represents As-terminated surface.…”

supporting

confidence: 94%

“…4b. This √ 2 × √ 2 structure is dominant on the cleaved surface [30]. This reconstruction expands the initial unit cell of a × a (left panel in Fig.…”

mentioning

confidence: 58%

See 1 more Smart Citation

Common ($π$,$π$) Band Folding and Surface Reconstruction in FeAs-Based Superconductors

Cai,

Xie,

Yang

et al. 2021

Preprint

Self Cite

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show abstract

“…This distance is √ 2 times the lattice constant. This observation is consistent with the previous STM results [30] and Fig. 4(b) represents Asterminated surface.…”

supporting

confidence: 93%

Common (π,π) Band Folding and Surface Reconstruction in FeAs-Based Superconductors

Cai¹,

Xie²,

Yang³

et al. 2021

Chinese Phys. Lett.

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High resolution angle-resolved photoemission spectroscopy (ARPES) measurements are carried out on CaKFe4As4, KCa2Fe4As4F2 and (Ba0.6K0.4)Fe2As2 superconductors. Clear evidence of band folding between the Brillouin zone center and corners with a (π,π) wave vector has been found from the measured Fermi surface and band structures in all the three kinds of superconductors. A dominant 2 × 2 surface reconstruction is observed on the cleaved surface of CaKFe4As4 by scanning tunneling microscopy (STM) measurements. We propose that the commonly observed 2 × 2 reconstruction in the FeAs-based superconductors provides a general scenario to understand the origin of the (π,π) band folding. Our observations provide new insights in understanding the electronic structure and superconductivity mechanism in iron-based superconductors.

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“…1a. Unlike many other FeSCs 16 , the cleavage of LiFeAs crystal occurs at a non-polar plane between the two Li layers (dashed line in Fig. 1a), presenting a good platform for investigating and tuning the unconventional superconductivity at nanoscale [17][18][19][20][21] .…”

mentioning

confidence: 99%

Two distinct superconducting states controlled by orientations of local wrinkles in LiFeAs

Cao

Liu

et al. 2021

Nat Commun

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For iron-based superconductors, the phase diagrams under pressure or strain exhibit emergent phenomena between unconventional superconductivity and other electronic orders, varying in different systems. As a stoichiometric superconductor, LiFeAs has no structure phase transitions or entangled electronic states, which manifests an ideal platform to explore the pressure or strain effect on unconventional superconductivity. Here, we observe two types of superconducting states controlled by orientations of local wrinkles on the surface of LiFeAs. Using scanning tunneling microscopy/spectroscopy, we find type-I wrinkles enlarge the superconducting gaps and enhance the transition temperature, whereas type-II wrinkles significantly suppress the superconducting gaps. The vortices on wrinkles show a C2 symmetry, indicating the strain effects on the wrinkles. By statistics, we find that the two types of wrinkles are categorized by their orientations. Our results demonstrate that the local strain effect with different directions can tune the superconducting order parameter of LiFeAs very differently, suggesting that the band shifting induced by directional pressure may play an important role in iron-based superconductivity.

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The As-surface of an iron-based superconductor CaKFe4As4

Cited by 8 publications

References 44 publications

Common ($π$,$π$) Band Folding and Surface Reconstruction in FeAs-Based Superconductors

Common ($π$,$π$) Band Folding and Surface Reconstruction in FeAs-Based Superconductors

Common (π,π) Band Folding and Surface Reconstruction in FeAs-Based Superconductors

Two distinct superconducting states controlled by orientations of local wrinkles in LiFeAs

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