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Evidence for Band Renormalizations in Strong-coupling Superconducting Alkali-fulleride Films
Authors:
J. S. Zhou,
R. Z. Xu,
X. Q. Yu,
F. J. Cheng,
W. X. Zhao,
X. Du,
S. Z. Wang,
Q. Q. Zhang,
X. Gu,
S. M. He,
Y. D. Li,
M. Q. Ren,
X. C. Ma,
Q. K. Xue,
Y. L. Chen,
C. L. Song,
L. X. Yang
Abstract:
There has been a long-standing debate about the mechanism of the unusual superconductivity in alkali-intercalated fulleride superconductors. In this work, using high-resolution angle-resolved photoemission spectroscopy, we systematically investigate the electronic structures of superconducting K3C60 thin films. We observe a dispersive energy band crossing the Fermi level with an occupied bandwidth…
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There has been a long-standing debate about the mechanism of the unusual superconductivity in alkali-intercalated fulleride superconductors. In this work, using high-resolution angle-resolved photoemission spectroscopy, we systematically investigate the electronic structures of superconducting K3C60 thin films. We observe a dispersive energy band crossing the Fermi level with an occupied bandwidth of about 130 meV. The measured band structure shows prominent quasiparticle kinks and a replica band involving high-energy Jahn-Teller active Hg(8) phonon mode, reflecting strong electron-phonon coupling in the system. The electron-phonon coupling constant is estimated to be about 1.2, which dominates the quasiparticle mass renormalization. Moreover, we observe an isotropic nodeless superconducting gap beyond the mean-field estimation. Both the large electron-phonon coupling constant and large reduced superconducting gap suggest a strong-coupling superconductivity in K3C60, while the electronic correlation effect is indicated by the observation of a waterfall-like band dispersion and the small bandwidth compared with the effective Coulomb interaction. Our results not only directly visualize the crucial band structure of superconducting fulleride but also provide important insights into the mechanism of the unusual superconductivity.
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Submitted 26 April, 2023;
originally announced April 2023.
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Crossed Luttinger Liquid Hidden in a Quasi-two-dimensional Material η-Mo4O11
Authors:
X. Du,
L. Kang,
Y. Y. Lv,
J. S. Zhou,
X. Gu,
R. Z. Xu,
Q. Q. Zhang,
Z. X. Yin,
W. X. Zhao,
Y. D. Li,
S. M. He,
D. Pei,
Y. B. Chen,
M. X. Wang,
Z. K. Liu,
Y. L. Chen,
L. X. Yang
Abstract:
Although the concept of Luttinger liquid (LL) that describes a one-dimensional (1D) interacting fermion system collapses in higher dimensions, it has been proposed to be closely related to many mysteries including the normal state of cuprate superconductor, unconventional metal, and quantum criticality. Therefore, the generalization of LL model to higher dimensions has attracted substantial resear…
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Although the concept of Luttinger liquid (LL) that describes a one-dimensional (1D) interacting fermion system collapses in higher dimensions, it has been proposed to be closely related to many mysteries including the normal state of cuprate superconductor, unconventional metal, and quantum criticality. Therefore, the generalization of LL model to higher dimensions has attracted substantial research attention. Here we systematically investigate the electronic structure of a quasi-2D compound η-Mo4O11 using high-resolution angle-resolved photoemission spectroscopy and ab-initio calculation. Remarkably, we reveal a prototypical LL behavior originating from the crossing quasi-1D chain arrays hidden in the quasi-2D crystal structure. Our results suggest that η-Mo4O11 materializes the long sought-after crossed LL phase, where the orthogonal orbital components significantly reduce the coupling between intersecting quasi-1D chains and therefore maintain the essential properties of LL. Our finding not only presents a realization of 2D LL, but also provides a new angle to understand non-Fermi liquid behaviors in other 2D and 3D quantum materials.
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Submitted 15 September, 2022;
originally announced September 2022.
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Observation of non-trivial topological electronic structure of orthorhombic SnSe
Authors:
H. J. Zheng,
W. J. Shi,
C. W. Wang,
Y. Y. Lv,
W. Xia,
B. H. Li,
F. Wu,
S. M. He,
K. Huang,
S. T. Cui,
C. Chen,
H. F. Yang,
A. J. Liang,
M. X. Wang,
Z. Sun,
S. H. Yao,
Y. B. Chen,
Y. F. Guo,
Q. X. Mi,
L. X. Yang,
M. S. Bahramy,
Z. K. Liu,
Y. L. Chen
Abstract:
Topological electronic structures are key to the topological classification of quantum materials and play an important role in their physical properties and applications. Recently, SnSe has attracted great research interests due to its superior thermoelectric performance. However, it's topological nature has long been ignored. In this work, by combining synchrotron-based angle-resolved photoemissi…
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Topological electronic structures are key to the topological classification of quantum materials and play an important role in their physical properties and applications. Recently, SnSe has attracted great research interests due to its superior thermoelectric performance. However, it's topological nature has long been ignored. In this work, by combining synchrotron-based angle-resolved photoemission spectroscopy and ab-initio calculations, we systematically investigated the topological electronic structure of orthorhombic SnSe. By identifying the continuous gap in the valence bands due to the band inversion and the topological surface states on its (001) surface, we establish SnSe as a strong topological insulator. Furthermore, we studied the evolution of the topological electronic structure and propose the topological phase diagram in SnSe1-xTex. Our work reveals the topological non-trivial nature of SnSe and provides new understandings of its intriguing transport properties.
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Submitted 14 April, 2022;
originally announced April 2022.