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Liu L, Liu X, Song P, Zhang L, Huang X, Zhang W, Zhang Z, Jia Y. Surface Superconductivity with High Transition Temperatures in Layered Ca nB n+1C n+1 Films. NANO LETTERS 2023; 23:1924-1929. [PMID: 36790290 DOI: 10.1021/acs.nanolett.2c05038] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/18/2023]
Abstract
Proposed by Ginzberg nearly 60 years ago, surface superconductivity refers to the emergent phenomenon that the electrons on or near the surface of a material becomes superconducting despite its bulk is nonsuperconducting. Here, based on first-principles calculations within density functional theory, we predict that the superconducting transition temperature Tc at the surfaces of CanBn+1Cn+1 (n = 1, 2, 3, ...) films can be drastically enhanced to ∼90 K from 8 K for bulk CaBC. Our detailed analyses reveal that structural symmetry reduction at surfaces induces pronounced carrier self-doping into the surface B-C layer of the films and shifts the σ-bonding states toward the Fermi level; furthermore, the in-plane stretching modes of the surface layers experience significant softening. These two effects work collaboratively to strongly enhance the electron-phonon coupling, which in turn results in much higher Tc values than the McMillian limit. These findings point to new material platforms for realizing unusually high-Tc surface superconductivity.
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Affiliation(s)
- Liangliang Liu
- Key Laboratory for Special Functional Materials of Ministry of Education, School of Materials Science and Engineering, Henan University, Kaifeng 475004, China
- Joint Center for Theoretical Physics, Henan University, Kaifeng 475004, China
| | - Xiaohan Liu
- Key Laboratory for Special Functional Materials of Ministry of Education, School of Materials Science and Engineering, Henan University, Kaifeng 475004, China
| | - Peng Song
- Key Laboratory for Special Functional Materials of Ministry of Education, School of Materials Science and Engineering, Henan University, Kaifeng 475004, China
- The Grainger College of Engineering, University of Illinois at Urbana-Champaign, Lincoln Hall, 702 S Wright Street, Urbana, Illinois 61801, United States
| | - Liying Zhang
- Key Laboratory for Special Functional Materials of Ministry of Education, School of Materials Science and Engineering, Henan University, Kaifeng 475004, China
- Joint Center for Theoretical Physics, Henan University, Kaifeng 475004, China
| | - Xiaowei Huang
- Key Laboratory for Special Functional Materials of Ministry of Education, School of Materials Science and Engineering, Henan University, Kaifeng 475004, China
| | - Weifeng Zhang
- Joint Center for Theoretical Physics, Henan University, Kaifeng 475004, China
| | - Zhenyu Zhang
- International Center for Quantum Design of Functional Materials (ICQD), Hefei National Laboratory for Physical Sciences at Microscale (HFNL), University of Science and Technology of China, Hefei, Anhui 230026, China
| | - Yu Jia
- Key Laboratory for Special Functional Materials of Ministry of Education, School of Materials Science and Engineering, Henan University, Kaifeng 475004, China
- Joint Center for Theoretical Physics, Henan University, Kaifeng 475004, China
- International Laboratory for Quantum Functional Materials of Henan, Zhengzhou University, Zhengzhou 450001, China
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Feig M, Bobnar M, Veremchuk I, Hennig C, Burkhardt U, Starke R, Kundys B, Leithe-Jasper A, Gumeniuk R. Two-gap superconductivity in Ag 1-x Mo 6S 8 Chevrel phase. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2017; 29:495603. [PMID: 29099390 DOI: 10.1088/1361-648x/aa97fd] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
The superconducting properties of [Formula: see text]Mo6S8 [[Formula: see text]] Chevrel phase [[Formula: see text] K] are studied on a sample compacted by spark plasma sintering. Both lower ([Formula: see text] mT) and the upper [[Formula: see text] T] critical magnetic fields are obtained from magnetization and electrical resistivity measurements for the first time. The analysis of the low-temperature electronic specific heat indicates [Formula: see text]Mo6S8 to be a two band superconductor with the energy gaps [Formula: see text] meV (95%) and [Formula: see text] meV (5%). Theoretical DFT calculations reveal a much stronger electron-phonon coupling in the studied Chevrel phase compared to earlier reports. Similar to MgB2, the Fermi surface of studied Chevrel phase is formed by two hole-like and one electron-like bands.
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Affiliation(s)
- Manuel Feig
- Institut für Experimentelle Physik, TU Bergakademie Freiberg, Leipziger StraÃe 23, 09596 Freiberg, Germany. Max-Planck-Institut für Chemische Physik fester Stoffe, Nöthnitzer StraÃe 40, 01187 Dresden, Germany
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Kunisada S, Adachi S, Sakai S, Sasaki N, Nakayama M, Akebi S, Kuroda K, Sasagawa T, Watanabe T, Shin S, Kondo T. Observation of Bogoliubov Band Hybridization in the Optimally Doped Trilayer Bi_{2}Sr_{2}Ca_{2}Cu_{3}O_{10+δ}. PHYSICAL REVIEW LETTERS 2017; 119:217001. [PMID: 29219391 DOI: 10.1103/physrevlett.119.217001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/23/2017] [Indexed: 06/07/2023]
Abstract
Using a laser-excited angle-resolved photoemission spectroscopy capable of bulk sensitive and high-energy resolution measurements, we reveal a new phenomenon of superconductors in the optimally doped trilayer Bi_{2}Sr_{2}Ca_{2}Cu_{3}O_{10+δ}. We observe a hybridization of the Bogoliubov bands derived from the inner and outer CuO_{2} planes with different magnitudes of energy gaps. Our data clearly exhibit the splitting of coherent peaks and the consequent enhancement of spectral gaps. These features are reproduced by model calculations, which indicate that the gap enhancement extends over a wide range of Fermi surface up to the antinode. The significant modulation of electron pairing uncovered here might be a crucial factor to achieve the highest critical temperature in the trilayer cuprates.
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Affiliation(s)
- So Kunisada
- ISSP, University of Tokyo, Kashiwa, Chiba 277-8581, Japan
| | - Shintaro Adachi
- ISSP, University of Tokyo, Kashiwa, Chiba 277-8581, Japan
- Graduate School of Science and Technology, Hirosaki University, Hirosaki, Aomori 036-8561, Japan
- MANA, National Institute for Materials Science, Tsukuba, Ibaraki 305-0047, Japan
| | - Shiro Sakai
- RIKEN Center for Emergent Matter Science (CEMS), Wako, Saitama 351-0198, Japan
| | - Nae Sasaki
- Graduate School of Science and Technology, Hirosaki University, Hirosaki, Aomori 036-8561, Japan
| | | | - Shuntaro Akebi
- ISSP, University of Tokyo, Kashiwa, Chiba 277-8581, Japan
| | - Kenta Kuroda
- ISSP, University of Tokyo, Kashiwa, Chiba 277-8581, Japan
| | - Takao Sasagawa
- Materials and Structures Laboratory, Tokyo Institute of Technology, Yokohama, Kanagawa 226-8503, Japan
| | - Takao Watanabe
- Graduate School of Science and Technology, Hirosaki University, Hirosaki, Aomori 036-8561, Japan
| | - Shik Shin
- ISSP, University of Tokyo, Kashiwa, Chiba 277-8581, Japan
| | - Takeshi Kondo
- ISSP, University of Tokyo, Kashiwa, Chiba 277-8581, Japan
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Patil S, Medicherla VRR, Ali K, Singh RS, Manfrinetti P, Wrubl F, Dhar SK, Maiti K. Observation of pseudogap in MgB 2. JOURNAL OF PHYSICS. CONDENSED MATTER : AN INSTITUTE OF PHYSICS JOURNAL 2017; 29:465504. [PMID: 29086758 DOI: 10.1088/1361-648x/aa8aa2] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
We investigate the electronic structure of a specially prepared highly dense conventional high temperature superconductor, MgB2, employing high resolution photoemission spectroscopy. The spectral evolution close to the Fermi energy is commensurate to BCS descriptions as expected. However, the spectra in the wider energy range reveal the emergence of a pseudogap much above the superconducting transition temperature indicating an apparent departure from the BCS scenario. The energy scale of the pseudogap is comparable to the energy of the [Formula: see text] phonon mode responsible for superconductivity in MgB2 and the pseudogap can be attributed to the effect of electron-phonon coupling on the electronic structure. These results reveal a scenario of the emergence of the superconducting gap within an electron-phonon coupling induced pseudogap and have significant implications in the study of high temperature superconductors.
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Affiliation(s)
- S Patil
- Department of Condensed Matter Physics and Materials' Science, Tata Institute of Fundamental Research, Homi Bhabha Road, Colaba, Mumbai-400005, India. Department of Physics, Indian Institute of Technology (Banaras Hindu University), Varanasi-221005, India
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AlZayed NS, Kityk IV, Soltan S, El-Naggar AM, Shahabuddin M. Laser induced infrared spectral shift of the MgB2:Cr superconductor films. SPECTROCHIMICA ACTA. PART A, MOLECULAR AND BIOMOLECULAR SPECTROSCOPY 2015; 136 Pt C:1698-1701. [PMID: 25467659 DOI: 10.1016/j.saa.2014.10.068] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/12/2014] [Revised: 10/05/2014] [Accepted: 10/19/2014] [Indexed: 06/04/2023]
Abstract
During illumination of the MgB2:Cr2O3 films it was established substantial spectral shift of the infrared spectra in the vicinity of 20-50cm(-1). The excitations were performed by nanosecond Er:glass laser operating at 1.54μm and by microsecond 10.6μm CO2 laser. The spectral shifts of the IR maxima were in opposite spectral directions for the two types of lasers. This one observed difference correlates well with spectral shift of their critical temperatures. The possible explanation is given by performance of DFT calculations of the charge density redistribution and the time kinetics of the photovoltaic response. To understand the kinetics of the photoinduced processes the time kinetics of photoresponse was done for the particular laser wavelengths.
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Affiliation(s)
- N S AlZayed
- Physics and Astronomy Department, College of Science, King Saud University, P.O. Box 2455, Riyadh 11451, Saudi Arabia
| | - I V Kityk
- Electrical Engineering Department, Czestochowa University Technology, PL-42-201, Armii Krajowej 17, Czestochowa, Poland.
| | - S Soltan
- Physics and Astronomy Department, College of Science, King Saud University, P.O. Box 2455, Riyadh 11451, Saudi Arabia; Max-Planck-Institut für Festkörperforschung, Heisenbergstr. 1, 70569 Stuttgart, Germany
| | - A M El-Naggar
- Physics and Astronomy Department, College of Science, King Saud University, P.O. Box 2455, Riyadh 11451, Saudi Arabia; Ain Shams University, Faculty of Science, Physics Dept., Abbassia, 11566 Cairo, Egypt
| | - M Shahabuddin
- Physics and Astronomy Department, College of Science, King Saud University, P.O. Box 2455, Riyadh 11451, Saudi Arabia
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Sharma N, Vugts P, Daniels C, Keuning W, Kohlhepp JT, Kurnosikov O, Koopmans B. Multi-channel Andreev reflection in Co-W nanocontacts fabricated using focused electron/ion beam induced deposition. NANOTECHNOLOGY 2014; 25:495201. [PMID: 25409909 DOI: 10.1088/0957-4484/25/49/495201] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/04/2023]
Abstract
We report multi-channel electron transport in nano-contacts fabricated using focused electron beam induced deposited (FEBID) cobalt and focused ion beam induced deposited (FIBID) tungsten. Anomalous Andreev reflection (AR) effect is observed to which the conventional Blonder-Tinkham-Klapwijk (BTK) fit cannot be applied. In specific, we have observed multiple number of shoulders near the AR peak, whose origin is unknown in literature. We explain this effect based on a simple model that takes into account the material properties of the FIBID grown W superconductor, as well as the specific interface properties that are an outcome of using FEBID/FIBID as a fabrication technique. We show that numerical calculations using the BTK approximation based on the consideration of multiple channels generate similar shoulders as we observed in the AR experiments. Electrical measurements and x-ray photoemission spectroscopy carried out on FIBID W deposits puts additional evidence towards multi-channel current transport occuring at the interface of the nanocontacts.
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Affiliation(s)
- N Sharma
- Department of Applied Physics, Center for NanoMaterials and COBRA Research Institute, Eindhoven University of Technology, PO Box 513, 5600 MB Eindhoven, The Netherlands
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Yang J, Hüvonen D, Nagel U, Rõõm T, Ni N, Canfield PC, Bud'ko SL, Carbotte JP, Timusk T. Optical spectroscopy of superconducting Ba0.55K0.45Fe2As2: evidence for strong coupling to low-energy bosons. PHYSICAL REVIEW LETTERS 2009; 102:187003. [PMID: 19518902 DOI: 10.1103/physrevlett.102.187003] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/07/2008] [Indexed: 05/27/2023]
Abstract
Normal state optical spectroscopy on single crystals of the new iron arsenide superconductor Ba0.55K0.45Fe2As2 shows that the infrared spectrum consists of two major components: a strong metallic Drude band and a well-separated midinfrared absorption centered at 0.7 eV. It is difficult to separate the two components unambiguously but several fits using Lorentzian peaks suggest a model with a Drude peak having a plasma frequency of 1.6 to 2.1 eV and a midinfrared peak with a plasma frequency of 2.5 eV. Detailed analysis of the frequency dependent scattering rate shows that the charge carriers interact with a broad bosonic spectrum extending beyond 100 meV with a very large coupling constant lambda=3.4 at low temperature. As the temperature increases this coupling weakens to lambda=0.78 at ambient temperature. This suggests a bosonic spectrum that is similar to what is seen in the lower Tc cuprates.
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Affiliation(s)
- J Yang
- Department of Physics and Astronomy, McMaster University, Hamilton, Ontario L8S 4M1, Canada
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Nakajima Y, Nakagawa T, Tamegai T, Harima H. Specific-heat evidence for two-gap superconductivity in the ternary-iron silicide Lu2Fe3Si5. PHYSICAL REVIEW LETTERS 2008; 100:157001. [PMID: 18518144 DOI: 10.1103/physrevlett.100.157001] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/28/2007] [Indexed: 05/26/2023]
Abstract
We report low-temperature specific-heat studies on the single-crystalline ternary-iron silicide superconductor Lu(2)Fe(3)Si(5) with T(c)=6.1 K down to approximately T(c)/20. We confirm a reduced normalized jump in specific heat at T(c), and find that the specific heat divided by temperature C/T shows a sudden drop at approximately T(c)/5 and goes to zero with further decreasing temperature. These results indicate the presence of two distinct superconducting gaps in Lu(2)Fe(3)Si(5), similar to the typical two-gap superconductor MgB(2). We also report Hall coefficients, band structure calculations, and the anisotropy of upper critical fields for Lu(2)Fe(3)Si(5), which support the anisotropic multiband nature and reinforce the existence of two superconducting gaps in Lu(2)Fe(3)Si(5).
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Affiliation(s)
- Y Nakajima
- Department of Applied Physics, The University of Tokyo, Hongo, Bunkyo-ku, Tokyo, Japan
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Kiss T, Shimojima T, Ishizaka K, Chainani A, Togashi T, Kanai T, Wang XY, Chen CT, Watanabe S, Shin S. A versatile system for ultrahigh resolution, low temperature, and polarization dependent laser-angle-resolved photoemission spectroscopy. THE REVIEW OF SCIENTIFIC INSTRUMENTS 2008; 79:023106. [PMID: 18315282 DOI: 10.1063/1.2839010] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
We have developed a low temperature ultrahigh resolution system for polarization dependent angle-resolved photoemission spectroscopy (ARPES) using a vacuum ultraviolet (vuv) laser (hnu=6.994 eV) as a photon source. With the aim of addressing low energy physics, we show the system performance with angle-integrated PES at the highest energy resolution of 360 mueV and the lowest temperature of 2.9 K. We describe the importance of a multiple-thermal-shield design for achieving the low temperature, which allows a clear measurement of the superconducting gap of tantalum metal with a T(c)=4.5 K. The unique specifications and quality of the laser source (narrow linewidth of 260 mueV, high photon flux), combined with a half-wave plate, facilitates ultrahigh energy and momentum resolution polarization dependent ARPES. We demonstrate the use of s- and p-polarized laser-ARPESs in studying the superconducting gap on bilayer-split bands of a high T(c) cuprate. The unique features of the quasi-continuous-wave vuv laser and low temperature enables ultrahigh-energy and -momentum resolution studies of the spectral function of a solid with large escape depth. We hope the present work helps in defining polarization dependent laser excited angle-resolved photoemission spectroscopy as a frontier tool for the study of electronic structure and properties of materials at the sub-meV energy scale.
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Affiliation(s)
- T Kiss
- Institute for Solid State Physics, University of Tokyo, Kashiwa, Chiba 277-8581, Japan.
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Cai YQ, Chow PC, Restrepo OD, Takano Y, Togano K, Kito H, Ishii H, Chen CC, Liang KS, Chen CT, Tsuda S, Shin S, Kao CC, Ku W, Eguiluz AG. Low-energy charge-density excitations in MgB2: Striking interplay between single-particle and collective behavior for large momenta. PHYSICAL REVIEW LETTERS 2006; 97:176402. [PMID: 17155487 DOI: 10.1103/physrevlett.97.176402] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/07/2006] [Indexed: 05/12/2023]
Abstract
A sharp feature in the charge-density excitation spectra of single-crystal MgB2, displaying a remarkable cosinelike, periodic energy dispersion with momentum transfer (q) along the c* axis, has been observed for the first time by high-resolution nonresonant inelastic x-ray scattering (NIXS). Time-dependent density-functional theory calculations show that the physics underlying the NIXS data is strong coupling between single-particle and collective degrees of freedom, mediated by large crystal local-field effects. As a result, the small-q collective mode residing in the single-particle excitation gap of the B pi bands reappears periodically in higher Brillouin zones. The NIXS data thus embody a novel signature of the layered electronic structure of MgB2.
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Affiliation(s)
- Y Q Cai
- National Synchrotron Radiation Research Center, Hsinchu 30076, Taiwan.
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Callaghan FD, Laulajainen M, Kaiser CV, Sonier JE. Field dependence of the vortex core size in a multiband superconductor. PHYSICAL REVIEW LETTERS 2005; 95:197001. [PMID: 16384012 DOI: 10.1103/physrevlett.95.197001] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/31/2005] [Indexed: 05/05/2023]
Abstract
The magnetic field dependence of the vortex core size in the multiband superconductor NbSe2 has been determined from muon spin rotation measurements. The spatially extended nature of the quasiparticle core states associated with the smaller gap leads to a rapid field-induced shrinkage of the core size at low fields, while the more tightly bound nature of the states associated with the larger gap leads to a field-independent core size for fields greater than 4 kOe. A simple model is proposed for the density of delocalized core states that establishes a direct relationship between the field-induced reduction of the vortex core size and the corresponding enhancement of the electronic thermal conductivity. We show that this model accurately describes both NbSe2 and the single-band superconductor V3Si.
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Affiliation(s)
- F D Callaghan
- Department of Physics, Simon Fraser University, Burnaby, British Columbia V5A 1S6, Canada
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Bianconi A. Feshbach Shape Resonance in Multiband Superconductivity in Heterostructures. ACTA ACUST UNITED AC 2005. [DOI: 10.1007/s10948-005-0047-5] [Citation(s) in RCA: 70] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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Geerk J, Schneider R, Linker G, Zaitsev AG, Heid R, Bohnen KP, v Löhneysen H. Observation of interband pairing interaction in a two-band superconductor: MgB2. PHYSICAL REVIEW LETTERS 2005; 94:227005. [PMID: 16090430 DOI: 10.1103/physrevlett.94.227005] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/20/2004] [Indexed: 05/03/2023]
Abstract
The recently discovered anisotropic superconductor MgB2 is the first of its kind showing the intriguing properties of two-band superconductivity. By tunneling experiments using thin film tunnel junctions, electron-coupled phonon spectra were determined showing that superconductivity in MgB2 is phonon mediated. In a further analysis, which involves first principles calculations, the strongest feature in these spectra could be traced back to the key quantity of two-band superconductivity, the interband pairing interaction. For the phonons, this interaction turns out quite selective. It involves mainly low-energy optical phonon modes, where the boron atoms move perpendicular to the boron planes.
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Affiliation(s)
- J Geerk
- Forschungszentrum Karlsruhe, Institut für Festkörperphysik, P.O.B. 3640, D-76021 Karlsruhe, Germany
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Ahn JR, Byun JH, Koh H, Rotenberg E, Kevan SD, Yeom HW. Mechanism of gap opening in a triple-band Peierls system: in atomic wires on Si. PHYSICAL REVIEW LETTERS 2004; 93:106401. [PMID: 15447426 DOI: 10.1103/physrevlett.93.106401] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/09/2004] [Indexed: 05/22/2023]
Abstract
One dimensional (1D) metals are unstable at low temperature undergoing a metal-insulator transition coupled with a periodic lattice distortion, a Peierls transition. Angle-resolved photoemission study for the 1D metallic chains of In on Si(111), featuring a metal-insulator transition and triple metallic bands, clarifies in detail how the multiple band gaps are formed at low temperature. In addition to the gap opening for a half-filled ideal 1D band with a proper Fermi surface nesting, two other quasi-1D metallic bands are found to merge into a single band, opening a unique but k-dependent energy gap through an interband charge transfer. This result introduces a novel gap-opening mechanism for a multiband Peierls system where the interband interaction is important.
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Affiliation(s)
- J R Ahn
- Center for Atomic Wires and Layers, Yonsei University, Seoul 120-749, Korea
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