Possible light-induced superconductivity in K3C60 at high temperature

Mitrano, Matteo; Cantaluppi, Alice; Nicoletti, D.; Kaiser, Stefan; Perucchi, A.; Lupi, S.; Pietro, P. Di; Pontiroli, Daniele; Riccò, Mauro; Clark, Stephen R. L.; Jaksch, Dieter; Cavalleri, Andrea

doi:10.1038/nature16522

Cited by 746 publications

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“…An ultrafast (typically femtosecond to picosecond) excitation with a laser pulse or electron beam may cause a transient phase conversion/promotion through electron-electron and/or electron-lattice interactions at the excited state, providing ultrafast control of the electronic state 25 . One of the most amazing phenomena reported recently is the transient photo-creation of possible room-temperature superconductivity in cuprate and C 60 -based superconductors 26,27 .…”

Section: Mottronicsmentioning

confidence: 99%

Emergent functions of quantum materials

2017

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Materials can harbour quantum many-body systems, most typically in the form of strongly correlated electrons in solids, that lead to novel and remarkable functions thanks to emergence-collective behaviours that arise from strong interactions among the elements. These include the Mott transition, high-temperature superconductivity, topological superconductivity, colossal magnetoresistance, giant magnetoelectric e ect, and topological insulators. These phenomena will probably be crucial for developing the next-generation quantum technologies that will meet the urgent technological demands for achieving a sustainable and safe society. Dissipationless electronics using topological currents and quantum spins, energy harvesting such as photovoltaics and thermoelectrics, and secure quantum computing and communication are the three major fields of applications working towards this goal. Here, we review the basic principles and the current status of the emergent phenomena and functions in materials from the viewpoint of strong correlation and topology.E mergence is a concept developed for many-body systems, indicating the properties, phenomena, and functions that never appear in the individual elements but are realized only when a huge number of elements get together 1 . Inside materials, emergent phenomena are often seen due to the interaction of electronic states; with recent developments on electronic states in solids schematically summarized in Fig. 1a. Electrons in solids have several degrees of freedom: charge, spin and orbital, and are characterized by the topological nature determined by the atomic potential on the crystal lattice structure, as schematically shown in Fig. 1b. These five attributes are coupled together and determine the overall responses to stimuli, which appear as materials' electrical, magnetic, optical, thermal, and mechanical properties.These collective electrons demonstrate various macroscopic quantum phenomena, the representative example of which is superconductivity. One of the big challenges in condensed matter physics is to increase the temperature (T c ) at which superconductivity can be observed to above room temperature. However, there are many other macroscopic quantum phenomena that are already observable above room temperature. One is magnetism (by the Bohr-van Leeuwen theorem), and the other is ferroelectricity 2,3 . Remarkably, there are common features of these three macroscopic quantum phenomena: the order parameter, which is of quantum origin, behaves as a classical quantity, and the quantum topology plays a crucial role.The topological nature of the electronic states is the key concept in the most recent developments in understanding quantum materials. The quantum Hall effect, topological insulators, and topological superconductors are all characterized by nontrivial topologies in Hilbert space. The Berry phase, which describes the connection and curvature of the subspace of Hilbert space, plays the central role in the unified principle to describe this topological nature 4 . ...

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Section: Mottronicsmentioning

confidence: 99%

Emergent functions of quantum materials

2017

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“…The density of the electromagnetic field at frequency ω and per molecule is E EMF (ω) = ω N (ω) , S16 so that, since in the units of Ref. [19] 1 Ω cm = 0.423 ps → Ω cm = 1.56 meV , the absorption rate in unit energy is τ (ω) 1.56 meV σ 1 (ω) Ω −1 cm −1 = W(ω) E EMF (ω) = 9 α ω J(ω, T ) .…”

Section: S15mentioning

confidence: 99%

“…The experiment of Ref. [19] is performed at fixed fluence, which implies at fixed value of S17 E EMF (ω) = ω N (ω). A fluence of 1 mJ cm −2 with a penetration depth of 220 nm [19] would correspond to an energy of the electromagnetic field per molecule of around E EMF (ω) = 207 meV.…”

Section: S15mentioning

confidence: 99%

“…[19] is performed at fixed fluence, which implies at fixed value of S17 E EMF (ω) = ω N (ω). A fluence of 1 mJ cm −2 with a penetration depth of 220 nm [19] would correspond to an energy of the electromagnetic field per molecule of around E EMF (ω) = 207 meV. Given the crudeness of our modelling and the neglect of other absorption processes, in the calculation we took a smaller E EMF (ω) = 100 meV, which provides results closer to the experiment.…”

Section: S15mentioning

confidence: 99%

“…1(a). There is instead an intriguing similarity between a long known [18,19] broad absorption peak that characterises the equilibrium IR response of K 3 C 60 and Rb 3 C 60 . This peak is present and strong in the equilibrium optical data of Ref.…”

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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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Review on Superconducting Materials

Hott

Kleiner

Wolf

et al. 2016

Digital Encyclopedia of Applied Physics

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The article contains sections titled: Introduction Cuprate High‐Temperature Superconductors Other Oxide Superconductors Iron‐Based Superconductors Other Chalcogenide Superconductors Heavy Fermion Superconductors Nitride Superconductors Organic and Other Carbon‐ and Silicon‐Based Superconductors Borides and Borocarbides

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Possible light-induced superconductivity in K3C60 at high temperature

Cited by 746 publications

References 40 publications

Emergent functions of quantum materials

Emergent functions of quantum materials

Cooling quasiparticles in A3C60 fullerides by excitonic mid-infrared absorption

Review on Superconducting Materials

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