DOCSLIB.ORG

Merohedral Disorder and Impurity Impacts on Superconductivity of Fullerenes

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Merohedral Disorder and Impurity Impacts on Superconductivity of Fullerenes ARTICLE https://doi.org/10.1038/s42005-021-00619-y OPEN Merohedral disorder and impurity impacts on superconductivity of fullerenes Shu-Ze Wang 1,5, Ming-Qiang Ren1,5, Sha Han1, Fang-Jun Cheng1, Xu-Cun Ma1,2, Qi-Kun Xue1,2,3,4 & ✉ Can-Li Song 1,2 Local quasiparticle states around impurities provide essential insight into the mechanism of unconventional superconductivity, especially when the candidate materials are proximate to an antiferromagnetic Mott-insulating phase. While such states have been reported in atom- based cuprates and iron-based compounds, they are unexplored in organic superconductors which feature tunable molecular orientation. Here we employ scanning tunneling microscopy 1234567890():,; and spectroscopy to reveal multiple forms of robustness of an exotic s-wave super- conductivity in epitaxial Rb3C60 films against merohedral disorder, non-magnetic single impurities and step edges at the atomic scale. Yu-Shiba-Rusinov (YSR) states, induced by deliberately incurred Fe adatoms that act as magnetic scatterers, have also been observed. The YSR bound states show abrupt spatial decay and vary in energy with the Fe adatom registry. These results and a doping-dependent study of superconductivity point towards local electron pairing in which the multiorbital electronic correlations and intramolecular phonons together drive the high-temperature superconductivity of doped fullerenes. 1 State Key Laboratory of Low-Dimensional Quantum Physics, Department of Physics, Tsinghua University, Beijing, China. 2 Frontier Science Center for Quantum Information, Beijing, China. 3 Beijing Academy of Quantum Information Sciences, Beijing, China. 4 Southern University of Science and Technology, ✉ Shenzhen, China. 5These authors contributed equally: Shu-Ze Wang, Ming-Qiang Ren. email: [email protected] COMMUNICATIONS PHYSICS | (2021) 4:114 | https://doi.org/10.1038/s42005-021-00619-y | www.nature.com/commsphys 1 ARTICLE COMMUNICATIONS PHYSICS | https://doi.org/10.1038/s42005-021-00619-y fi isorders, impurities in an otherwise homogeneous or every C60 is perpendicular to the surface. Speci cally, nanoscale Dgranular superconductor, are often undesired aliens domains with two distinct C60 orientations, related by 44.48° because they may hinder observations of intrinsic prop- rotation about the [111] axis (Fig. 1b), develop and are partially erties of the host material1–4. Yet, dopant impurities could also opacified in red and orange, respectively. This is reminiscent of be a double-edged sword by leading not only to emergent high- the two standard orientations of C60 that randomly occur and temperature (Tc) superconductivity in cuprates and iron cause merohedral disorder in face-centered cubic-structured tri- 5,6 28–30 pnictides but also to uncovering the underlying mechanism of valent fullerides . The C60 orientations are more disordered in unconventional superconductivity7–13, especially as multiple regions between adjacent merohedral domains. In order to unusual states are complexly intertwined in these materials14,15. quantify the merohedral disorder, the averaged orientational θ 39 θ = θ −θ Whereas it has been well documented that non-magnetic correlation functions <cos( ij)> , in which ij i j denotes impurities little affect Cooper pairs in conventional the angle between nearest-neighbor C60 molecules (i.e., i and j), superconductors16,17, they induce local bound states in the are calculated and summarized in Fig. 1c. The orientational superconducting gap (Δ) and suppress superconductivity via pair correlation decreases with alkali metal radius, indicating breaking for unconventional pairing symmetries, for example, in increasing merohedral disorder. This most probably arises from a 8,17–20 a d-wave or s± wave superconductor . Recently, anomalous weakening of Coulomb repulsion between adjacent trivalent C60 enhancement of superconductivity by disorder is another ions associated with the lattice expansion40, which otherwise 37 example of impurities revealing their fundamental significance stabilizes a long-ranged merohedral order in the K3C60 films ,to 21–24 θ = fi for low-dimensional superconductors .Itistherefore wit <cos( ij)> 1. For a speci cK3C60 or Rb3C60 compound, it tempting to consider impurities as a blessing in disguise to unveil turns out that the orientational correlation and thus merohedral the physics of candidate superconductors4–20,tostrivefor disorder change little with the film thickness (Supplementary Δ optimal superconductivity with Tc and reaching their respec- Figure 1). tive maxima25, and to create exotic electronic states that never Tunneling spectroscopy of fullerides probes the local density of emerge from pure superconducting systems26. quasiparticle states (DOS) and measures the superconducting Unlike atom-based superconductors, an organic super- energy gap at the Fermi level (EF). In Fig. 1d, we compare fi conductor is a synthetic molecule-based compound that uniquely tunneling dI/dV spectra on various trivalent fulleride lms A3C60 exhibits additional degrees of freedom related to its molecular (A = K, Rb, Cs) with the same thickness of 9 ML. Although two orientation. Consequently, inequivalent molecular orientations sharp DOS peaks develop ~−0.4 eV and 0.1 eV in the merohed- fi 37 take place. Such orientational (merohedral) disorder has been rally ordered K3C60 lms , they are largely smoothed out in both 27,28 seen early in pure and doped fullerenes , but its impact, either Rb3C60 and RbCs2C60 with the great merohedral disorder. This harmful29,30 or irrelevant31,32, to superconductivity of fullerenes, observation is consistent with the theoretical calculation that the is highly controversial. In addition, the fullerides represent an merohedral disorder would blur t1u-derived DOS peaks in 41 unusual category of organic superconductors in which the mul- A3C60 . It is, however, worth noting that the low-lying DOS tiorbital electronic correlations and electron–phonon interactions width estimated as the spacing between the two conductance fi are both suggested to be signi cant to reach high-Tc minima below and above EF (>1.2 eV, see the two dashed lines in 33,34 fi superconductivity . Under this context, a systematic study of Fig. 1d) is signi cantly larger than the commonly argued t1u impurity effects on superconductivity of doped fullerenes would bandwidth of ∼0.5 eV41,42. Such a discrepancy might originate provide justification of the previously advocated s-wave pairing from the Jahn-Teller (JT) instabilities and Coulomb interactions symmetry35–37, as well as advance the understanding of the omitted by three-band first-principles calculations41,42.Incon- superconducting state. However, such an experiment is unex- sideration of JT-induced subband splitting and electronic correla- 34,43,44 plored and the roles played by magnetic and non-magnetic tions, the t1u bandwidth could be substantially increased impurities remain unknown in fulleride superconductors. and accords with our observation. A further enhancement of In this work, we use a molecular beam epitaxy (MBE) tech- electronic correlations U in the most expanded Cs3C60 films fi nique to grow epitaxial lms of rubidium (Rb)-doped fullerenes pushes the t1u-derived DOS toward higher energy and opens a with thickness and filling tunability, and probe the local quasi- Mott-insulating gap38, in contrast to the superconducting ground particle states in the vicinity of various impurities at the atomic state in K3C60 and Rb3C60 (Fig. 1d). scale by means of cryogenic scanning tunneling microscopy Despite nanoscale merohedral disorder, superconductivity fi (STM) and spectroscopy (STS). Distinct from the super- develops well in Rb3C60 lms. We unambiguously reveal this 37 conducting K3C60 films without merohedral disorder and the by measuring the spatial dependence of superconducting gaps at 38 fi insulating Cs3C60 ones with great merohedral disorder , mer- the atomic scale via STS, as exempli ed in Fig. 1e. Even on the ohedrally disordered Rb3C60 films are superconducting. This boundaries between adjacent merohedral domains, the super- allows for atomic-scale visualization of merohedral disorder conducting gaps exhibit clear coherence peaks (blue curves) and impact on superconductivity of fullerenes, which, together with a are immune to the local merohedral disorder (Fig. 1a). This is fi fi detailed STS study of magnetic and non-magnetic impurities, further con rmed in Cs and Rb co-doped RbCs2C60 lms, which shows that superconductivity of fullerenes is entirely consistent imprint a comparably large merohedral disorder but exhibit a = with local s-wave pairing. By studying the thickness and electron- superconducting transition temperature up to Tc 23 K (Sup- fi Δ lling dependence of superconducting gap in RbxC60, we fur- plementary Figure 2). Nevertheless, the superconducting spectra ther establish a unified phase diagram of fullerenes in which the present some spatial electronic inhomogeneities, especially for fi = fi optimal superconductivity always develops at half- lling (x 3). the coherence peaks. A careful examination of Rb3C60 lms at varied thicknesses and spatial locations reveals that the coherence peak amplitude scales inversely with Δ (Supplemen- Results tary Figure 3). This is unexpected by the conventional wisdom of Merohedral disorder and its impact on superconductivity. Bardeen-Cooper-Schrieffer (BCS) picture, and we ascribe to Figure 1a depicts a representative STM topography of nine coexistence of competing order, e.g., the ubiquitous pseudogap fi 37 monolayer
Load more

Recommended publications
  • Process for Producing a Metal Fulleride
    Europäisches Patentamt *EP001199281A1* (19) European Patent Office Office européen des brevets (11) EP 1 199 281 A1 (12) EUROPEAN PATENT APPLICATION (43) Date of publication: (51) Int Cl.7: C01B 31/02 24.04.2002 Bulletin 2002/17 (21) Application number: 00122854.3 (22) Date of filing: 20.10.2000 (84) Designated Contracting States: • Dubitzky, Yuri A. AT BE CH CY DE DK ES FI FR GB GR IE IT LI LU 20159 Milano (IT) MC NL PT SE • Ricco, Mauro Designated Extension States: 43100 Parma (IT) AL LT LV MK RO SI • Sartori, Andrea 43010 Fontana (Parma) (IT) (71) Applicant: PIRELLI CAVI E SISTEMI S.p.A. 20126 Milano (IT) (74) Representative: Giannesi, Pier Giovanni et al Pirelli S.p.A. (72) Inventors: Industrial Property Dept. • Zaopo, Antonio Viale Sarca, 222 20137 Milano (IT) 20126 Milano (IT) (54) Process for producing a metal fulleride (57) The present invention relates to a process for acting in a liquid medium: 1) a first metal fulleride having, producing a metal fulleride. In particular, the present in- as counterion, a cation of a first metal forming a salt sub- vention relates to a process for producing a metal ful- stantially insoluble in said liquid medium, and 2) a salty leride by an ion exchange reaction in a liquid medium, of a second metal substantially soluble in said liquid me- preferably in liquid ammonia. More particularly, the dium, so as to produce a second metal fulleride having, present invention relates to a process for producing a as counterion, a cation of said second metal.
    [Show full text]
  • Discrete Fulleride Anions and Fullerenium Cations
    UC Riverside UC Riverside Previously Published Works Title Discrete fulleride anions and fullerenium cations. Permalink https://escholarship.org/uc/item/60b5m71z Journal Chemical reviews, 100(3) ISSN 0009-2665 Authors Reed, CA Bolskar, RD Publication Date 2000-03-01 DOI 10.1021/cr980017o Peer reviewed eScholarship.org Powered by the California Digital Library University of California Chem. Rev. 2000, 100, 1075−1120 1075 Discrete Fulleride Anions and Fullerenium Cations Christopher A. Reed* and Robert D. Bolskar Department of Chemistry, University of CaliforniasRiverside, Riverside, California 92521-0403 Received June 22, 1999 Contents iii. Anisotropy 1100 iv. Problem of the Sharp Signals 1101 I. Introduction, Scope, and Nomenclature 1075 v. Origins of Sharp Signals 1102 II. Electrochemistry 1078 vi. The C O Impurity Postulate 1103 A. Reductive Voltammetry 1078 120 vii. The Dimer Postulate 1104 B. Oxidative Voltammetry 1079 2- C. Features of the C60 EPR Spectrum 1106 III. Synthesis 1079 3- D. Features of the C60 EPR Spectrum 1107 A. Chemical Reduction of Fullerenes to 1079 4- 5- Fullerides E. Features of C60 and C60 EPR Spectra 1107 i. Metals as Reducing Agents 1080 F. EPR Spectra of Higher Fullerides 1107 ii. Coordination and Organometallic 1080 G. EPR Spectra of Fullerenium Cations 1108 Compounds as Reducing Agents X. Chemical Reactivity 1108 iii. Organic/Other Reducing Agents 1081 A. Introduction 1108 B. Electrosynthesis of Fullerides 1081 B. Fulleride Basicity 1109 C. Chemical Oxidation of Fullerenes to 1081 C. Fulleride Nucleophilicity/Electron Transfer 1109 Fullerenium Cations D. Fullerides as Intermediates 1110 IV. Electronic (NIR) Spectroscopy 1082 E. Fullerides as Catalysts 1111 A. Introduction 1082 F.
    [Show full text]
  • Electrochemical Synthesis of Lithium Fullerides
    Chem. Met. Alloys 6 (2013) 40-42 Ivan Franko National University of Lviv www.chemetal-journal.org Electrochemical synthesis of lithium fullerides A.O. ZUL’FIGAROV 1, V.A. POTASKALOV 1, A.P. POMYTKIN 1, A.A. ANDRIIKO 1*, D.V. SHCHUR 2, O.A. KRIUKOVA 3, V.G. KHOMENKO 3 1 Chair of General and Inorganic Chemistry, National Technical University of Ukraine “Kyiv Polytechnic Institute”, 37 Prospekt Peremogy, Kyiv, Ukraine 2 Institute of Material Science Problems, National Academy of Sciences of Ukraine, 3 Krzhyzhanovskogo St., Kyiv, Ukraine 3 National University of Technologies and Design, 2 Nemyrovycha-Danchenka St., Kyiv, Ukraine * Corresponding author. E-mail: [email protected] Received June 3, 2013; accepted June 19, 2013; available on-line November 4, 2013 The electrochemical reaction of Li with fullerene in an aprotic electrolyte was studied. It was found that a lithium-rich fulleride with approximate formula Li 10 C60 can be obtained in the presence of a catalyst. This amount of Li is irreversibly incorporated into the structure. Additionally, 4-5 atoms can be introduced reversibly, thus allowing cycling the material with an initial reversible capacity of about 180 mAh·g -1. The pyrolysis product of a heterometal complex with monoaminoethanol ligands is shown to be a good catalyst for this process. Fullerene / Lithium fulleride / Electrochemical synthesis Introduction The cathodic reduction of Li + ions on a fullerene- based electrode under controlled current was chosen Since the discovery of carbon allotrope fullerenes in for this purpose. In some of the experiments, the 1985 [1] , a large number of researches have been electrode contained additives of a trinuclear complex devoted to the chemistry of these substances.
    [Show full text]
  • Hydrocarbon-Soluble, Hexaanionic Fulleride Complexes of Magnesium† Cite This: Chem
    Chemical Science View Article Online EDGE ARTICLE View Journal | View Issue Hydrocarbon-soluble, hexaanionic fulleride complexes of magnesium† Cite this: Chem. Sci.,2019,10,10755 a b a All publication charges for this article Samuel R. Lawrence, C. Andre´ Ohlin, David B. Cordes, have been paid for by the Royal Society Alexandra M. Z. Slawin a and Andreas Stasch *a of Chemistry Ar Ar The reaction of the magnesium(I) complexes [{( nacnac)Mg}2], ( nacnac ¼ HC(MeCNAr)2,Ar¼ Dip (2,6- iPr2C6H3), Dep (2,6-Et2C6H3), Mes (2,4,6-Me3C6H2), Xyl (2,6-Me2C6H3)) with fullerene C60 afforded Ar a series of hydrocarbon-soluble fulleride complexes [{( nacnac)Mg}nC60], predominantly with n ¼ 6, 4 and 2. 13C{1H} NMR spectroscopic studies show both similarities (n ¼ 6) and differences (n ¼ 4, 2) to previously characterised examples of fulleride complexes and materials with electropositive metal ions. Ar The molecular structures of [{( nacnac)Mg}nC60] with n ¼ 6, 4 and 2 can be described as inverse Ar + nÀ coordination complexes of n [( nacnac)Mg] ions with C60 anions showing predominantly ionic 6À metal–ligand interactions, and include the first well-defined and soluble complexes of the C60 ion. Ar + 6À Experimental studies show the flexible ionic nature of the {( nacnac)Mg} /C60 coordination bonds. Creative Commons Attribution 3.0 Unported Licence. Received 2nd August 2019 DFT calculations on the model complex [{(Menacnac)Mg} C ](Menacnac ¼ HC(MeCNMe) ) support the Accepted 6th October 2019 6 60 2 6À 6À formulation as an ionic complex with a central C60 anion and comparable frontier orbitals to C60 DOI: 10.1039/c9sc03857d with a small HOMO–LUMO gap.
    [Show full text]
  • INFORMATION to USERS This Manuscript Has Been Reproduced
    INFORMATION TO USERS This manuscript has been reproduced from the microfilm master. UMI films the text directly from the original or copy submitted. Thus, some thesis and dissertation copies are in typewriter face, while others may be from any type of computer printer. The quality of this reproduction is dependent upon the quality of the copy submitted. Broken or indistinct print, colored or poor quality illustrations and photographs, print bleedthrough, substandard margins, and improper alignment can adversely affect reproduction. In the unlikely event that the author did not send UMI a complete manuscript and there are missing pages, these will be noted. Also, if unauthorized copyright material had to be removed, a note will indicate the deletion. Oversize materials (e.g., maps, drawings, charts) are reproduced by sectioning the original, beginning at the upper left-hand comer and continuing from left to right in equal sections with small overlaps. Each original is also photographed in one exposure and is included in reduced form at the back of the book. Photographs included in the original manuscript have been reproduced xerographically in this copy. Higher quality 6" x 9" black and white photographic prints are available for any photographs or illustrations appearing in this copy for an additional charge. Contact UMI directly to order. A Bell & Howell information Company 300 North Zeeb Road. Ann Arbor. Ml 48106-1346 USA 313/761-4700 800/521-0600 NMR Studies of Alkali Fulleride Superconductors DISSERTATION Presented in Partial Fulfillment of the Requirements for the Degree of Doctor of Philosophy in the Graduate School of The Ohio State University By Victor A.
    [Show full text]
  • Tuneable Graphite Intercalates for Hydrogen Storage
    Tuneable graphite intercalates for hydrogen storage Arthur Lovell A Thesis presented for the degree of Doctor of Philosophy Condensed Matter and Materials Physics Department of Physics and Astronomy University College London England September 2007 Declaration I, Arthur Lovell, con¯rm that the work presented in this thesis is my own. Where information has been derived from other sources, I con¯rm that this has been indicated in the thesis. The work in this thesis is based on research carried out at the Condensed Matter and Materials Physics Group, the Department of Physics and Astronomy, University College London, England. No part of this thesis has been submitted elsewhere for any other degree or quali¯cation. Copyright °c 2007 by Arthur Lovell. \The copyright of this thesis rests with the author. No quotations from it should be published without the author's prior written consent and information derived from it should be acknowledged". ii Tuneable graphite intercalates for hydrogen storage Arthur Lovell Submitted for the degree of Doctor of Philosophy September 2007 Abstract The development of hydrogen as an energy transfer mechanism is of great importance to alleviate environmental damage and economic destabilisation caused by over-reliance on oil, as long as the hydrogen can be generated re- newably. To be suitable for road transport applications, safe and compact hydrogen storage systems need to be developed, the primary technological motivation for this PhD project which investigates hydrogen absorbed into graphite intercalation compounds (GICs), to gain a fundamental physical un- derstanding of the sorption processes to improve such materials' capacity for hydrogen storage.
    [Show full text]
  • Discrete Fulleride Anions and Fullerenium Cations
    Chem. Rev. 2000, 100, 1075−1120 1075 Discrete Fulleride Anions and Fullerenium Cations Christopher A. Reed* and Robert D. Bolskar Department of Chemistry, University of CaliforniasRiverside, Riverside, California 92521-0403 Received June 22, 1999 Contents iii. Anisotropy 1100 iv. Problem of the Sharp Signals 1101 I. Introduction, Scope, and Nomenclature 1075 v. Origins of Sharp Signals 1102 II. Electrochemistry 1078 vi. The C O Impurity Postulate 1103 A. Reductive Voltammetry 1078 120 vii. The Dimer Postulate 1104 B. Oxidative Voltammetry 1079 2- C. Features of the C60 EPR Spectrum 1106 III. Synthesis 1079 3- D. Features of the C60 EPR Spectrum 1107 A. Chemical Reduction of Fullerenes to 1079 4- 5- Fullerides E. Features of C60 and C60 EPR Spectra 1107 i. Metals as Reducing Agents 1080 F. EPR Spectra of Higher Fullerides 1107 ii. Coordination and Organometallic 1080 G. EPR Spectra of Fullerenium Cations 1108 Compounds as Reducing Agents X. Chemical Reactivity 1108 iii. Organic/Other Reducing Agents 1081 A. Introduction 1108 B. Electrosynthesis of Fullerides 1081 B. Fulleride Basicity 1109 C. Chemical Oxidation of Fullerenes to 1081 C. Fulleride Nucleophilicity/Electron Transfer 1109 Fullerenium Cations D. Fullerides as Intermediates 1110 IV. Electronic (NIR) Spectroscopy 1082 E. Fullerides as Catalysts 1111 A. Introduction 1082 F. Fullerides as Ligands 1111 n- B. C60 Fullerides 1082 G. Fullerenium Cations 1112 C. C70 and Higher Fullerenes 1085 XI. Conclusions and Future Directions 1113 D. Fullerenium Cations 1086 XII. Acknowledgments 1114 E. Diffuse Interstellar Bands 1086 XIII. References 1114 V. Vibrational Spectroscopy 1087 A. Infrared Spectroscopy 1087 B. Raman Spectroscopy 1087 I. Introduction, Scope, and Nomenclature VI.
    [Show full text]
  • Coexistence of Full-Gap Superconductivity and Pseudogap in Two-Dimensional Fullerides
    Coexistence of full-gap superconductivity and pseudogap in two-dimensional fullerides Ming-Qiang Ren1, Sha Han1, Shu-Ze Wang1, Jia-Qi Fan1, Can-Li Song1,2 †, Xu-Cun Ma1,2 †, Qi-Kun Xue1,2,3† 1 State Key Laboratory of Low-Dimensional Quantum Physics, Department of Physics, Tsinghua University, Beijing 100084, China 2 Frontier Science Center for Quantum Information, Beijing 100084, China 3 Beijing Academy of Quantum Information Sciences, Beijing 100193, China Alkali-fulleride superconductors with a maximum critical temperature Tc 40 K exhibit similar 1-5 electronic phase diagram with unconventional high-Tc superconductors where the superconductivity resides proximate to a magnetic Mott-insulating state3-6. However, distinct 7 from cuprate compounds, which superconduct through two-dimensional (2D) CuO2 planes , 8,9 alkali fullerides are attributed to the three-dimensional (3D) members of high-Tc family . Here, we employ scanning tunneling microscopy (STM) to show that trilayer K3C60 displays fully gapped strong coupling s-wave superconductivity that coexists spatially with a cuprate-like pseudogap state above Tc 22 K and within vortices. A precise control of electronic correlations and doping reveals that superconductivity occurs near a superconductor-Mott insulator transition (SMIT) and reaches maximum at half-filling. The s-wave symmetry retains over the entire phase diagram, which, in conjunction with an abrupt decline of superconductivity below half-filling, demonstrates that alkali fullerides are predominantly phonon-mediated superconductors, although the multiorbital electronic correlations also come into play. †To whom correspondence should be addressed. Email: [email protected], [email protected], [email protected] 1 10,11 Trivalent fullerides A3C60 (A = alkali metals) have historically been, albeit not universally , thought of as conventional Bardeen-Cooper-Schrieffer (BCS) superconductors12,13.
    [Show full text]
  • Heavy Alkali-Metal Intercalated Fullerenes Under High Pressure and High Temperature Conditions: Rb6c60 and Cs6c60 Roberta Poloni
    Heavy alkali-metal intercalated fullerenes under high pressure and high temperature conditions: Rb6C60 and Cs6C60 Roberta Poloni To cite this version: Roberta Poloni. Heavy alkali-metal intercalated fullerenes under high pressure and high temperature conditions: Rb6C60 and Cs6C60. Physics [physics]. Université Claude Bernard - Lyon I, 2007. English. tel-00194610 HAL Id: tel-00194610 https://tel.archives-ouvertes.fr/tel-00194610 Submitted on 6 Dec 2007 HAL is a multi-disciplinary open access L’archive ouverte pluridisciplinaire HAL, est archive for the deposit and dissemination of sci- destinée au dépôt et à la diffusion de documents entific research documents, whether they are pub- scientifiques de niveau recherche, publiés ou non, lished or not. The documents may come from émanant des établissements d’enseignement et de teaching and research institutions in France or recherche français ou étrangers, des laboratoires abroad, or from public or private research centers. publics ou privés. No d'ordre 214{2007 Ann´ee 2007 THESE` pr´esent´ee devant l'UNIVERSITE´ CLAUDE BERNARD - LYON 1 pour l'obtention du DIPLOME DE DOCTORAT arr^et´e du 7 aout^ 2006 pr´esent´ee et soutenue publiquement le 31 Octobre 2007 par Roberta POLONI TITRE: Heavy alkali metal-intercalated fullerenes under high pressure and high temperature conditions: Rb6C60 and Cs6C60 Directeur de th`ese Prof. Alfonso SAN MIGUEL JURY: Pascale Launois Rapporteur Bertil Sundqvist Rapporteur Xavier Blase Pr´esident Marco Saitta Examinateur Kosmas Prassides Examinateur Alfonso San Miguel Directeur Sakura Pascarelli Codirecteur 2 Contents Introduction i 1 The C60 fullerene and the heavy alkali metal-intercalated fullerenes 1 1.1 Motivation .
    [Show full text]
  • Merohedral Disorder and Impurity Impacts on Superconductivity of Fullerenes
    Merohedral disorder and impurity impacts on superconductivity of fullerenes Shu-Ze Wang1*, Ming-Qiang Ren1*, Sha Han1, Fang-Jun Cheng1, Xu-Cun Ma1,2, Qi-Kun Xue1,2,3,4, Can-Li Song1,2† 1State Key Laboratory of Low-Dimensional Quantum Physics, Department of Physics, Tsinghua University, Beijing 100084, China 2Frontier Science Center for Quantum Information, Beijing 100084, China 3Beijing Academy of Quantum Information Sciences, Beijing 100193, China 4Southern University of Science and Technology, Shenzhen 518055, China Local quasiparticle states around impurities provide essential insight into the mechanism of unconventional superconductivity, especially when the candidate materials are proximate to an antiferromagnetic Mott-insulating phase. While such states have been reported in atom- based cuprates and iron-based compounds, they are unexplored in organic superconductors which feature tunable molecular orientation. Here we employ scanning tunneling microscopy and spectroscopy to reveal multiple forms of robustness of an exotic s-wave superconductivity in epitaxial Rb3C60 films against merohedral disorder, non-magnetic single impurities and step edges at the atomic scale. Also observed have been Yu-Shiba-Rusinov (YSR) states induced by deliberately incurred Fe adatoms that act as magnetic scatterers. The bound states display abrupt spatial decay and vary in energy with the Fe adatom registry. Our results and the universal optimal superconductivity at half-filling point towards local electron pairing in which the multiorbital electronic correlations and intramolecular phonons together drive the high- temperature superconductivity of doped fullerenes. *Both authors contributed equally to this work. 1 †To whom correspondence should be addressed. Email: [email protected] 2 Disorder, impurities in an otherwise homogeneous superconductor, are often undesired aliens because they may hinder observations of intrinsic properties of the host material1-3.
    [Show full text]
  • University of London Thesis
    REFERENCE ONLY UNIVERSITY OF LONDON THESIS Degree Year Name of Author C~ A C O P Y R IG H T This is a thesis accepted for a Higher Degree of the University of London. It is an unpublished typescript and the copyright is held by the author. All persons consulting the thesis must read and abide by the Copyright Declaration below. COPYRIGHT DECLARATION I recognise that the copyright of the above-described thesis rests with the author and that no quotation from it or information derived from it may be published without the prior written consent of the author. LOANS Theses may not be lent to individuals, but the Senate House Library may lend a copy to approved libraries within the United Kingdom, for consultation solely on the premises of those libraries. Application should be made to: Inter-Library Loans, Senate House Library, Senate House, Malet Street, London WC1E 7HU. REPRODUCTION University of London theses may not be reproduced without explicit written permission from the Senate House Library. Enquiries should be addressed to the Theses Section of the Library. Regulations concerning reproduction vary according to the date of acceptance of the thesis and are listed below as guidelines. A. Before 1962. Permission granted only upon the prior written consent of the author. (The Senate House Library will provide addresses where possible). B. 1962- 1974. In many cases the author has agreed to permit copying upon completion of a Copyright Declaration. C. 1975 - 1988. Most theses may be copied upon completion of a Copyright Declaration. D. 1989 onwards. Most theses may be copied.
    [Show full text]
  • Superconductivity, High Temperature Superconductivity
    SUPERCONDUCTIVITY, HIGH TEMPERATURE SUPERCONDUCTIVITY Magnetization relaxation in superconducting fulleride K3C60 single crystals V. A. Buntar, F. M. Sauerzopf, and H. W. Weber Atominstitut der O¨ sterreichischen Universita¨ten, A-1020 Wien, Austria A. G. Buntar Vinnitsa State Technical University, 286021 Vinnitsa, Ukraine H. Kumani and M. Haluska Institut fu¨r Festko¨rperphysik, Universita¨t Wien, A-1090 Wien, Austria ~Submitted September 10, 1996! Fiz. Nizk. Temp. 23, 365–371 ~April 1997! Magnetic relaxation processes in superconducting fulleride K3C60 are investigated on monocrystalline samples in a wide range of temperatures and magnetic fields. A logarithmic time dependence M(t) of magnetization is observed in samples with 100% of superconducting phase. The normalized relaxation rate increases with temperature in the entire range of magnetic fields. The flux creep activation energy ranges from 10 to 80 meV, and its temperature dependence has a peak. It has been concluded from the results of measurements on samples with nonideal stoichiometry that inhomogeneities strongly affect the relaxation processes and can mask the logarithmic dependence M(t) completely. © 1997 American Institute of Physics. @S1063-777X~97!00104-7# 1. INTRODUCTION also observed in fullerides. However, these two types of su- perconductors exhibit considerable differences. Supercon- The measurements of relaxation magnetization serve as ductivity in HTS compounds is two-dimensional and a universal method for studying irreversible properties of strongly anisotropic, while FS are three-dimensional super- type II superconductors and provide information on pinning conductors with a cubic lattice. of Abrikosov vortices, their dynamic properties, the nature of Thus, an analysis of time relaxation of magnetization in kinetic state, and so on.
    [Show full text]