Shear-induced superconductivity in<i>β</i>-di[-Bis(ethylene- dithio)tetrathiafulvalene]triiodide<i>[β</i>-(BEDT-TTF<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mrow><mml:mo>)</mml:mo></mml:mrow><mml:mrow><mml:mn>2</mml:mn></mml:mrow></mml:msub></mml:mrow></mml:math><mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:mrow><mml:msub><mml:mrow><mml:mi mathvariant="normal">I</mml:mi></mml:mrow><mml:mrow><mml:mn>3</mml:mn><mml:mo>]

Schirber, J. E.; Azevedo, L. J.; Kwak, J. F.; Venturini, E. L.; Leung, P. T.; Beno, M. A.; Wang, H. H.; Williams, Jack M.

doi:10.1103/physrevb.33.1987

Cited by 82 publications

(3 citation statements)

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“…The behavior of the β-(ET) 2 I 3 crystals under pressure was studied, and a drastic change in superconductivity was found, with the increase of T c to 8 K at a low pressure (Figure ). , The T − P phase diagram was investigated and it was established that the β-(ET) 2 I 3 crystals can exist in two superconducting states: a low-temperature one (β L ) with T c of 1.5 K under ambient pressure and a high-temperature one (β H ) with T c of 8 K at P ≈ 400 bar. − The limits of stability of both phases were determined. The β H phase can be retained at ambient pressure by cooling the sample under pressure ( P > 400 bar) followed by the pressure release at low temperatures. , On such a treatment, the β H phase exists at atmospheric pressure at T < 150 K, above which it converts to the β L phase (Figure ). − It was asserted in ref that the high- T c state in β-(ET) 2 I 3 cannot be accessed by only hydrostatic pressure but requires, in addition, a substantial shear component. When pure hydrostatic pressure was applied to a sample through careful isobaric freezing of He, a high- T c state was not observed.…”

Section: 32 β-(Et)2x; X = I3 Ibr2 I2br and (Ibr2)07(i3)03mentioning

confidence: 99%

“…When pure hydrostatic pressure was applied to a sample through careful isobaric freezing of He, a high- T c state was not observed. On the other hand, fast freezing of liquid He 4 or solidification of pressure-transmitting liquid produces a shear component in pressure applied to the crystal, and under these conditions, the high- T c state was produced . No reasonable explanation has been found so far for the role of shear stress in superconductivity or the lattice modulation.…”

Section: 32 β-(Et)2x; X = I3 Ibr2 I2br and (Ibr2)07(i3)03mentioning

confidence: 99%

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Molecular Conductors and Superconductors Based on Trihalides of BEDT-TTF and Some of Its Analogues

2004

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Section: 32 β-(Et)2x; X = I3 Ibr2 I2br and (Ibr2)07(i3)03mentioning

confidence: 99%

Section: 32 β-(Et)2x; X = I3 Ibr2 I2br and (Ibr2)07(i3)03mentioning

confidence: 99%

Molecular Conductors and Superconductors Based on Trihalides of BEDT-TTF and Some of Its Analogues

2004

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“…Early on it was also realized that ET molecules have intramolecular degrees of freedom, namely the configurations of their two ethylene endgroups (see Fig. 3), which can either be aligned parallel (eclipsed, E) or canted (staggered, S) [7][8][9][10][11][12][13][14][15][16][17]. The energetically favorable configuration is not universal for different anions X and packing motifs.…”

mentioning

confidence: 99%

Influence of molecular conformations on the electronic structure of organic charge transfer salts

2015

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We report ab-initio calculations for the electronic structure of organic charge transfer salts κ-(ET)2Cu[N(CN)2]Br, κ-(ET)2Cu[N(CN)2]I, κ -(ET)2Cu[N(CN)2]Cl and κ-(ET)2Cu2(CN)3. These materials show an ordering of the relative orientation of terminal ethylene groups in the BEDT-TTF molecules at finite temperature and our calculations correctly predict the experimentally observed ground state molecular conformations (eclipsed or staggered). Further, it was recently demonstrated that the ethylene endgroup relative orientations can be used to reversibly tune κ-(ET)2Cu[N(CN)2]Br through a metal-insulator transition. Using a tight-binding analysis, we show that the molecular conformations of ethylene endgroups are intimately connected to the electronic structure and significantly influence hopping and Hubbard repulsion parameters. Our results place κ-(ET)2Cu[N(CN)2]Br in eclipsed and staggered configurations on opposite sides of the metal-insulator transition.PACS numbers: 71.10. Fd, 71.15.Mb, 71.20.Rv, 74.70.Kn Quasi-two dimensional charge transfer salts κ-(BEDT-TTF) 2 X, where BEDT-TTF stands for bisethylenedithio-tetrathiafulvalene, often abbreviated as ET, constitute a fascinating family of materials due to their rich phase diagrams comprising metallic, superconducting, Mott insulating and spin-liquid phases [1][2][3][4].These electronic properties of ET-based materials are very sensitive to disorder. Irradiation experiments have shown that lattice disorder lowers the T c of κ-(ET) 2 Cu(SCN) 2 [5] and causes electron localization in κ-(ET) 2 Cu[N(CN) 2 ]Br [6]. Early on it was also realized that ET molecules have intramolecular degrees of freedom, namely the configurations of their two ethylene endgroups (see Fig. 3), which can either be aligned parallel (eclipsed, E) or canted (staggered, S) [7][8][9][10][11][12][13][14][15][16][17]. The energetically favorable configuration is not universal for different anions X and packing motifs. For some materials a glass-like freezing of the ethylene endgroups upon cooling has been observed [7,8,[15][16][17][18][19].Especially the first ambient pressure ET-based superconductor β-(ET) 2 I 3 attracted a lot of interest, because its T c can be enhanced from 1.5 K to 8 K by forcing the ET molecules, which are endgroup disordered at ambient pressure, to assume staggered configuration through application of shear and pressure [7-11, 20, 21]. Recently, it was shown that ethylene endgroup disorder can be used to reversibly tune κ-(ET) 2 Cu[N(CN) 2 ]Br through a metal to insulator transition [17,22,23].It is believed that materials κ-(ET) 2 X have a common phase diagram, which is mainly controlled by the value of the on-site Coulomb repulsion U over the electronic bandwidth [24]. Changes in physical properties in the presence of ethylene endgroup disorder have so far been interpreted as a consequence of lattice disorder, with the exception of recent scanning tunneling spectroscopy experiments [25]. Surprisingly, the effect of different ethylene endgroup configurations on the ele...

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Existierende und hypothetische intermediärvalente AgII/AgIII- und AgII/AgI-Fluoride als potentielle Supraleiter

Grochala

Hoffmann

2001

Angew. Chem.

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Um ihr Potential als leitende oder supraleitende Materialien abzuschätzen, untersuchen wir die Kristallstrukturen und die magnetischen Eigenschaften der heute bekannten etwa 100 binären, ternären und quaternären AgII‐ und AgIII‐Fluoride im festen Zustand. Das AgII‐Kation befindet sich in diesen Verbindungen im Allgemeinen in einer verzerrt‐oktaedrischen Umgebung, entweder in einer unendlichen [AgF]+‐Kette oder in [AgF2]‐Schichten. Manchmal findet man auch diskrete quadratisch‐planare [AgF4]2−‐ Ionen. Das AgIII‐Kation tritt meist in der Form isolierter quadratisch‐planarer [AgF4]−‐Ionen auf. AgIII(d8)‐Systeme sind typischerweise diamagnetisch. Demgegenüber führt das reichhaltige Spektrum an koordinativen Umgebungen des AgII (d9) in binären und ternären Fluoriden zu sehr vielfältigen magnetischen Eigenschaften, die von Paramagnetismus über temperaturunabhängigen Paramagnetismus (charakteristisch für halbgefüllte Bänder und metallisches Verhalten) und Antiferromagnetismus bis hin zu schwachem Ferromagnetismus reichen. AgII und AgIII weisen dieselben d‐Elektronenzahlen auf wie CuII (d9) bzw. CuIII (d8). F− und O2− sind isoelektronische Ionen mit abgeschlossener Schale (s2p6). Sowohl F− als auch O2− sind Liganden mit schwachem Feld. Im Lichte dieser Ähnlichkeiten und auf der Basis einiger experimenteller Hinweise untersuchen wir Analogien zwischen den supraleitenden Cupraten (CuII/CuIII‐O2−‐ und CuII/CuI‐O2−‐Systemen) und den formal gemischtvalenten AgII/AgIII‐F−‐ und AgII/AgI‐F−‐Phasen. Zu diesem Zweck berechneten wir die elektronischen Strukturen einiger strukturell charakterisierter binärer und ternärer Fluoride von AgI, AgII und AgIII und vergleichen die Ergebnisse mit ähnlichen Rechnungen für Oxocuprat‐Supraleiter. Elektronische Niveaus in der Nachbarschaft des Fermi‐Niveaus (x2−y2 oder z2) haben üblicherweise stark gemischten Ag(d)/F(p)‐Charakter und sind Ag‐F‐antibindend, sodass sie die Möglichkeit zur effizienten Schwingungskopplung bieten (wie dies für d9‐Systeme mit bedeutendem kovalenten Bindungsanteil typisch ist). Gemäß unseren Rechnungen liegt dies nicht nur an einer zufälligen Koinzidenz der Orbitalenergien; überraschenderweise weist die Ag‐F‐Bindung in AgII‐ und AgIII‐Fluoriden tatsächlich bedeutende kovalente Anteile auf. Die elektronische Zustandsdichte am Fermi‐Niveau (DOSF) von Silberfluoriden wie auch die Frequenzen der Metall‐Ligand‐Streckschwingungsmoden sind denen von Kupferoxiden ähnlich. Die oben geschilderten Eigenschaften deuten darauf hin, dass geeignet löcher‐ oder elektronendotierte AgII‐Fluoride gute BCS‐Supraleiter sein könnten. Wir analysieren ein Komproportionierungs‐/Disproportionierungs‐Gleichgewicht in löcherdotierten AgII‐Fluoriden und das mögliche Auftreten von Löchern im F(p)‐Band. Möglicherweise lässt sich bei diesen Fluoriden eine Überschneidung der Kurven der ionischen und der kovalenten Bindung (entsprechend der Formulierung AgIII‐F−/AgII‐F0) erreichen, was zu einem erheblichen Anstieg der Schwingungskopplung führen würde.

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Shear-induced superconductivity inβ-di[-Bis(ethylene- dithio)tetrathiafulvalene]triiodide[β-(BEDT-TTF)2I3]

Cited by 82 publications

References 11 publications

Molecular Conductors and Superconductors Based on Trihalides of BEDT-TTF and Some of Its Analogues

Molecular Conductors and Superconductors Based on Trihalides of BEDT-TTF and Some of Its Analogues

Influence of molecular conformations on the electronic structure of organic charge transfer salts

Existierende und hypothetische intermediärvalente AgII/AgIII- und AgII/AgI-Fluoride als potentielle Supraleiter

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