Dynamic Jahn-Teller Effects in Isolated<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:msubsup><mml:mi mathvariant="normal">C</mml:mi><mml:mn>60</mml:mn><mml:mo>−</mml:mo></mml:msubsup></mml:math>Studied by Near-Infrared Spectroscopy in a Storage Ring

Tomita, S.; Andersen, J. U.; Bonderup, E.; Hvelplund, P.; Liu, B.; Nielsen, Steen Brøndsted; Pedersen, U.; Rangama, Jimmy; Hansen, Klavs; Echt, Olof

doi:10.1103/physrevlett.94.053002

Cited by 42 publications

(42 citation statements)

References 29 publications

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“…A similar lifetime (2.2±0.2 ps) was found upon population of a vibronic state of the 2 E g electronically excited state of C − 60 by the fs-pump/probe photoelectron spectroscopy upon excitation at 775 nm [23]. We therefore also explored whether the first excited state of matrix isolated C − 60 (absorption maximum at 1066 nm in gas phase [24]) shows measurable fluorescence. In matrixes also containing fullerene anions we did not observe a LIF signal from C At higher temperatures solid krypton scatters less than at lower temperatures.…”

Section: Lifetime Estimationmentioning

confidence: 89%

Near-IR Photoluminescence of C₆₀⁺

2017

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Section: Lifetime Estimationmentioning

confidence: 89%

Near-IR Photoluminescence of C₆₀⁺

2017

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“…Electronic structure calculations [9] suggests that λ 1.25. Near IR absorption spectra of C − 60 [14,15] show a main peak at ∆ * = 1150 − 1163 meV, which is the bare t 1u → t 1g excitation energy ∆ reduced by a JahnTeller contribution. In the antiadiabatic limit we are using here,…”

Section: S31 Anti-adiabatic Regimementioning

confidence: 99%

“…1 (b). This tantalising observation has already elicited various theoretical efforts [12][13][14][15][16], where it was mainly assumed, as in the original work [11], that TO phonon IR absorption acts as the crucial ingredient increasing the pairing efficiency. Here we follow another route directly inspired by experimental features, which leads to a totally different perspective.…”

mentioning

confidence: 99%

Cooling quasiparticles in A3C60 fullerides by excitonic mid-infrared absorption

et al. 2017

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Long after its discovery superconductivity in alkali fullerides A 3 C 60 still challenges conventional wisdom. The freshest inroad in such ever-surprising physics is the behaviour under intense infrared (IR) excitation. Signatures attributable to a transient superconducting state extending up to temperatures ten times higher than the equilibrium T c ∼ 20 K have been discovered in K 3 C 60 after ultra-short pulsed IR irradiation -an effect which still appears as remarkable as mysterious. Motivated by the observation that the phenomenon is observed in a broad pumping frequency range that coincides with the mid-infrared electronic absorption peak still of unclear origin, rather than to TO phonons as has been proposed, we advance here a radically new mechanism. First, we argue that this broad absorption peak represents a "super-exciton" involving the promotion of one electron from the t 1u half-filled state to a higher-energy empty t 1g state, dramatically lowered in energy by the large dipole-dipole interaction acting in conjunction with Jahn Teller effect within the enormously degenerate manifold of t 1u 2 t 1g 1 states. Both long-lived and entropy-rich because they are triplets, the IR-induced excitons act as a sort of cooling mechanism that permits transient superconductive signals to persist up to much larger temperatures.Superconducting alkali doped fullerenes A 3 C 60 are molecular compounds where several actors play together to determine an intriguing physical behaviour. The high icosahedral symmetry of C 60 arXiv:1704.05613v1 [cond-mat.str-el] 19 Apr 2017 2 implies, prior to intermolecular hybridisation, a large degeneracy of the molecular orbitals, thus a strong electronic response to JT molecular distortions lowering that symmetry. In particular, the t 1u LUMO, which accommodates the three electrons donated by the alkali metals, is threefold degenerate and JT coupled to eight fivefold-degenerate molecular vibrations of H g symmetry, which mediate the pairing [1]. The JT effect, favouring low spin, is partly hindered by (Coulomb) Hund's rule exchange, which favours high spin. Therefore the overall singlet pairing strength g, though still sizeable, is way too small compared to the charging energy of each C 3− 60 to justify by simple arguments why A 3 C 60 are s-wave superconductors. The explanation of this puzzle proposed in [2,3] and vindicated by recent experiments emphasises the crucial role of a parent Mott insulating state where the JT coupling effectively inverts Hund's rules, the molecular ground state therefore turning to spin S = 1/2 rather than S = 3/2 [4]. A S = 1/2 antiferromagnetic insulating phase is indeed the ground state in over-expanded NH 3 K 3 C 60 [5,6] and in Cs 3 C 60 [7] at ambient pressure. In the metallic state, attained under pressure in Cs 3 C 60 and at ambient pressure in K 3 C 60 and Rb 3 C 60 , the incipient Mott localisation slows down the coherent motion of quasiparticles while undressing them from charge correlations. As a result, the singlet pairing strength g eventual...

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“…From these measurements, it is concluded that C 60 À is dynamically distorted to presumably D 3d symmetry. 13 Previously, it was shown that neutral gas-phase C 60 can be efficiently excited using tunable IR light from a free-electron laser. [21][22][23] When the radiation is resonant with an IR-allowed transition in the molecule, the sequential absorption of hundreds of photons can take place, resulting in very hot molecules.…”

Section: Introductionmentioning

confidence: 99%

“…6 For C 60 and other fullerenes, this distortion has been investigated both theoretically [6][7][8][9] and experimentally. [10][11][12][13][14][15] Especially C 60 À serves as a model system for the JT effect in highly symmetrical molecules and the molecule is expected to experience a distortion from icosahedral (I h ) to either D 5d or D 3d symmetry. 6 In the solid state, Rb 1 C 60 has been investigated using IR reflectivity measurements.…”

Section: Introductionmentioning

confidence: 99%

IR spectroscopy of gas-phase C60−

Kupser

Steill

Meijer

et al. 2008

Phys. Chem. Chem. Phys.

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We present the IR spectrum of the gas-phase C 60 À anion. The C 60 À anions are mass-selected and trapped in an ion cyclotron mass spectrometer cell. The spectrum is obtained by recording the yield of electrons following infrared multiple photon absorption and subsequent electron detachment of the anions. Two bands are observed that correlate to two of the four IR-allowed transitions in neutral C 60 . The results show that the higher frequency band is strongly shifted from its position in neutral C 60 and is a sensitive marker for the charge state. The band positions and intensities are compared to results obtained by theory as well as to known bands in solid samples and good agreement is found.

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Dynamic Jahn-Teller Effects in IsolatedC60−Studied by Near-Infrared Spectroscopy in a Storage Ring

Cited by 42 publications

References 29 publications

Near-IR Photoluminescence of C₆₀⁺

Near-IR Photoluminescence of C₆₀⁺

Cooling quasiparticles in A3C60 fullerides by excitonic mid-infrared absorption

IR spectroscopy of gas-phase C60−

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Dynamic Jahn-Teller Effects in IsolatedC60−Studied by Near-Infrared Spectroscopy in a Storage Ring

Cited by 42 publications

References 29 publications

Near-IR Photoluminescence of C60+

Near-IR Photoluminescence of C60+

Cooling quasiparticles in A3C60 fullerides by excitonic mid-infrared absorption

IR spectroscopy of gas-phase C60−

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Product

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Near-IR Photoluminescence of C₆₀⁺

Near-IR Photoluminescence of C₆₀⁺