Neutron Spectroscopy of Superconducting Fullerides

1992 ◽  
Vol 270 ◽  
Author(s):  
Kosmas Prassides ◽  
Christos Christides ◽  
John Tomkinson ◽  
Matthew J. Rosseinsky ◽  
D. W. Murphy ◽  
...  
Keyword(s):  
Low Temperatures ◽  
High Energy ◽  
Inelastic Neutron ◽  
Low Energy ◽  
Vibrational Modes ◽  
Phonon Coupling ◽  
Phonon Spectra ◽  
Electron Phonon Coupling ◽  
Wide Range ◽  
Mechanism Of Superconductivity

ABSTRACTThe phonon spectra of pristine fullerene, superconducting K3C60 and saturation-doped Rb6C60 measured by inelastic neutron scatteringin the energy range 2.5 - 200 meV at low temperatures reveal substantial broadening of five-fold degenerate Hg intramolecular vibrational modes both in the low-energy radial and the high-energy tangential part of the spectrum. This provides strong evidence for a traditional phonon-mediated mechanism of superconductivity in the fullerides but with an electron-phonon coupling strength distributed over a wide range of energies (33-195 meV) as a result of the finite curvature of the fullerene spherical cage.

NEUTRON SCATTERING STUDIES OF FULLERENES

1992 ◽  
Vol 06 (23n24) ◽  
pp. 4007-4011 ◽  
Author(s):  
KOSMAS PRASSIDES
Keyword(s):  
Neutron Scattering ◽  
Electrostatic Interactions ◽  
Inelastic Neutron Scattering ◽  
High Energy ◽  
Inelastic Neutron ◽  
First Order Phase Transition ◽  
Phonon Spectra ◽  
Wide Range ◽  
Cubic Structure ◽  
First Order Phase

At low temperature, crystalline C 60 adopts a simple cubic structure whose stability is driven by optimisation of the intermolecular electrostatic interactions. Above 85 K, molecular motion is no longer frozen and the molecules shuffle between nearly-degenerate orientations, differing in energy by 11.4(3) meV. At 260 K, a first-order phase transition leads to a face-centred cubic structure, characterised by rapid isotropic molecular reorientational motion. In C 70, orientational ordering occurs near 270 K. The phonon spectra of C 60, superconducting K 3 C 60 and saturation-doped Rb 6 C 60 measured by inelastic neutron scattering in the energy range 0–200meV reveal substantial broadening in the superconducting fulleride of five-fold degenerate H g intramolecular modes both in the low-energy radial and the high-energy tangential part of the spectrum. This confirms the predictions of models based on intramolecular phonon-mediated pairing. The electron-phonon coupling strength is distributed over a wide range of energies (33–195 meV) as a result of the finite curvature of the fullerene spherical cage. No evidence is found for any significant electron-librational coupling.

scholarly journals Low-Energy Electron Damage to Condensed-Phase DNA and Its Constituents

2021 ◽  
Vol 22 (15) ◽  
pp. 7879
Author(s):  
Yingxia Gao ◽  
Yi Zheng ◽  
Léon Sanche
Keyword(s):  
Condensed Phase ◽  
Genetic Material ◽  
High Energy ◽  
Dna Lesions ◽  
Low Energy ◽  
Experimental Investigations ◽  
Experimental Conditions ◽  
Strand Breaks ◽  
Sequence Of Events ◽  
Wide Range

The complex physical and chemical reactions between the large number of low-energy (0–30 eV) electrons (LEEs) released by high energy radiation interacting with genetic material can lead to the formation of various DNA lesions such as crosslinks, single strand breaks, base modifications, and cleavage, as well as double strand breaks and other cluster damages. When crosslinks and cluster damages cannot be repaired by the cell, they can cause genetic loss of information, mutations, apoptosis, and promote genomic instability. Through the efforts of many research groups in the past two decades, the study of the interaction between LEEs and DNA under different experimental conditions has unveiled some of the main mechanisms responsible for these damages. In the present review, we focus on experimental investigations in the condensed phase that range from fundamental DNA constituents to oligonucleotides, synthetic duplex DNA, and bacterial (i.e., plasmid) DNA. These targets were irradiated either with LEEs from a monoenergetic-electron or photoelectron source, as sub-monolayer, monolayer, or multilayer films and within clusters or water solutions. Each type of experiment is briefly described, and the observed DNA damages are reported, along with the proposed mechanisms. Defining the role of LEEs within the sequence of events leading to radiobiological lesions contributes to our understanding of the action of radiation on living organisms, over a wide range of initial radiation energies. Applications of the interaction of LEEs with DNA to radiotherapy are briefly summarized.

scholarly journals Acoustic phonon lifetimes limit thermal transport in methylammonium lead iodide

2018 ◽  
Vol 115 (47) ◽  
pp. 11905-11910 ◽  
Author(s):  
Aryeh Gold-Parker ◽  
Peter M. Gehring ◽  
Jonathan M. Skelton ◽  
Ian C. Smith ◽  
Dan Parshall ◽  
...  
Keyword(s):  
Lattice Dynamics ◽  
Acoustic Phonon ◽  
Optoelectronic Devices ◽  
High Energy ◽  
High Energy Resolution ◽  
Phonon Coupling ◽  
Lead Iodide ◽  
Phonon Modes ◽  
Electron Phonon Coupling ◽  
Methylammonium Lead Iodide

Hybrid organic–inorganic perovskites (HOIPs) have become an important class of semiconductors for solar cells and other optoelectronic applications. Electron–phonon coupling plays a critical role in all optoelectronic devices, and although the lattice dynamics and phonon frequencies of HOIPs have been well studied, little attention has been given to phonon lifetimes. We report high-precision momentum-resolved measurements of acoustic phonon lifetimes in the hybrid perovskite methylammonium lead iodide (MAPI), using inelastic neutron spectroscopy to provide high-energy resolution and fully deuterated single crystals to reduce incoherent scattering from hydrogen. Our measurements reveal extremely short lifetimes on the order of picoseconds, corresponding to nanometer mean free paths and demonstrating that acoustic phonons are unable to dissipate heat efficiently. Lattice-dynamics calculations using ab initio third-order perturbation theory indicate that the short lifetimes stem from strong three-phonon interactions and a high density of low-energy optical phonon modes related to the degrees of freedom of the organic cation. Such short lifetimes have significant implications for electron–phonon coupling in MAPI and other HOIPs, with direct impacts on optoelectronic devices both in the cooling of hot carriers and in the transport and recombination of band edge carriers. These findings illustrate a fundamental difference between HOIPs and conventional photovoltaic semiconductors and demonstrate the importance of understanding lattice dynamics in the effort to develop metal halide perovskite optoelectronic devices.

scholarly journals Filled Skutterudite Antimonides: Validation of the Electron-Crystal Phonon-Glass Approach to New Thermoelectric Materials

1997 ◽  
Vol 478 ◽  
Author(s):  
D. Mandrus ◽  
B. C. Sales ◽  
V. Keppens ◽  
B. C. Chakoumakos ◽  
P. Dai ◽  
...  
Keyword(s):  
Specific Heat ◽  
Thermoelectric Materials ◽  
Inelastic Neutron Scattering ◽  
Inelastic Neutron ◽  
Low Energy ◽  
Vibrational Modes ◽  
Weakly Bound ◽  
Filled Skutterudite ◽  
Resonant Ultrasound ◽  
Electron Crystal

AbstractAfter a brief review of the transport and thermoelectric properties of filled skutterudite antimonides, we present resonant ultrasound, specific heat, and inelastic neutron scattering results that establish the existence of two low-energy vibrational modes in the filled skutterudite LaFe3CoSb12. It is likely that at least one of these modes represents the localized, incoherent vibrations of the La ion in an oversized atomic “cage.” These results support the usefulness of weakly bound, “rattling” ions for the improvement of thermoelectric performance.

Direct evidence of the importance of electron-phonon coupling inLa2CuO4: Photoinduced ir-active vibrational modes

1987 ◽  
Vol 36 (13) ◽  
pp. 7252-7255 ◽  
Author(s):  
Y. H. Kim ◽  
A. J. Heeger ◽  
L. Acedo ◽  
G. Stucky ◽  
F. Wudl
Keyword(s):  
Direct Evidence ◽  
Vibrational Modes ◽  
Phonon Coupling ◽  
Electron Phonon Coupling

Influence of Electron-Phonon Coupling Coefficient on Properties in Femtosecond Laser Ablation

2015 ◽  
Vol 814 ◽  
pp. 144-149 ◽  
Author(s):  
Ran Xiang ◽  
Xin Yu Tan ◽  
Hui Li Wei
Keyword(s):  
Laser Ablation ◽  
Femtosecond Laser ◽  
Electron Temperature ◽  
Coupling Coefficient ◽  
Femtosecond Laser Ablation ◽  
High Energy ◽  
Rapid Decline ◽  
Phonon Coupling ◽  
Electron Phonon Coupling ◽  
Coupling Time

Thermodynamics effects generated by femtosecond laser ablation are very important. In this work, the numerical simulation of high-energy femtosecond laser ablation especially the electro-phonon coupling coefficient influence of high-energy femtosecond laser ablation on metal target was studied. A new two-temperature model (TTM) which considered the effects of electron density of states (DOS) on electron-phonon coupling coefficient was first established, then the temperature evolvement for electron and lattice in different electro-phonon coupling coefficient G, and the effect of G on electron temperature and lattice temperature and electron-phonon coupling time were emphatically analyzed. The results showed that the electron-phonon coupling coefficient strongly affected the surface electron temperature and coupling time in the femtosecond laser ablation. The smaller the electron-phonon coupling coefficient was, the more the energy transmission from electronic to ion subsystem. As a result, the smaller the value of electron-phonon coupling coefficient, a more rapid decline for the temperature of electronic sub-system achieved. This work will offer help for the future investigation of material fabrication by femtosecond laser ablation.

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