Strong electron–phonon coupling influences carrier transport and thermoelectric performances in group-IV/V elemental monolayers

AbstractThe interactions between electrons and phonons play the key role in determining the carrier transport properties in semiconductors. In this work, comprehensive investigations on full electron–phonon (el–ph) couplings and their influences on carrier mobility and thermoelectric (TE) performances of 2D group IV and V elemental monolayers are performed, and we also analyze the selection rules on el–ph couplings using group theory. For shallow n/p-dopings in Si, Ge, and Sn, ZA/TA/LO phonon modes dominate the intervalley scatterings. Similarly strong intervalley scatterings via ZA/TO phonon modes can be identified for CBM electrons in P, As, and Sb, and for VBM holes, ZA/TA phonon modes dominate intervalley scatterings in P while LA phonons dominate intravalley scatterings in As and Sb. By considering full el–ph couplings, the TE performance for these two series of monolayers are predicted, which seriously downgrades the thermoelectric figures of merits compared with those predicted by the constant relaxation time approximation.

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The effect of strong electron-rattling phonon coupling on some superconducting properties

Canadian Journal of Physics ◽

10.1139/cjp-2018-0283 ◽

2019 ◽

Vol 97 (5) ◽

pp. 472-476

Author(s):

Samin Tajik ◽

Božidar Mitrović ◽

Frank Marsiglio

Keyword(s):

Temperature Dependence ◽

Coupling Parameter ◽

Nmr Relaxation ◽

Superconducting Gap ◽

Phonon Coupling ◽

Phonon Modes ◽

Strong Electron ◽

Particle Decay ◽

Electron Phonon Coupling ◽

The One

Using the Eliashberg theory of superconductivity we have examined several properties of a model in which electrons are coupled only to rattling phonon modes represented by a sharp peak in the electron–phonon coupling function. Our choice of parameters was guided by experiments on β-pyrochlore oxide superconductor KOs2Os6. We have calculated the temperature dependence of the superconducting gap edge; the quasi-particle decay rate; the NMR relaxation rate assuming that the coupling between the nuclear spins and the conduction electrons is via a contact hyperfine interaction, which would be appropriate for the O-site in KOs2Os6; and the microwave conductivity. We examined the limit of very strong coupling by considering three values of the electron–phonon coupling parameter λ = 2.38, 3, and 5 and did not assume that the rattler frequency Ω0 is temperature dependent in the superconducting state. We obtained a very unusual temperature dependence of the superconducting gap edge Δ(T), very much like the one extracted from photoemission experiments on KOs2O6.

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Single Molecule Fluorescence Spectroscopy of PSI Trimers from Arthrospira platensis: A Computational Approach

Molecules ◽

10.3390/molecules24040822 ◽

2019 ◽

Vol 24 (4) ◽

pp. 822 ◽

Cited By ~ 4

Author(s):

Roman Pishchalnikov ◽

Vladimir Shubin ◽

Andrei Razjivin

Keyword(s):

Single Molecule ◽

Fluorescence Spectra ◽

Arthrospira Platensis ◽

Phonon Coupling ◽

Phonon Modes ◽

Spectroscopy Analysis ◽

Strong Electron ◽

Zero Phonon Line ◽

Electron Phonon Coupling ◽

Single Molecule Fluorescence Spectroscopy

Based on single molecule spectroscopy analysis and our preliminary theoretical studies, the linear and fluorescence spectra of the PSI trimer from Arthrospira platensis with different realizations of the static disorder were modeled at cryogenic temperature. Considering the previously calculated spectral density of chlorophyll, an exciton model for the PSI monomer and trimer including the red antenna states was developed taking into account the supposed similarity of PSI antenna structures from Thermosynechococcus e., Synechocystis sp. PCC6803, and Arthrospira platensis. The red Chls in the PSI monomer were assumed to be in the nearest proximity of the reaction center. The PSI trimer model allowed the simulation of experimentally measured zero phonon line distribution of the red states considering a weak electron-phonon coupling for the antenna exciton states. However, the broad absorption and fluorescence spectra of an individual emitter at 760 nm were calculated by adjusting the Huang-Rhys factors of the chlorophyll lower phonon modes assuming strong electron-phonon coupling.

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THERMODYNAMIC CHARACTERISTICS OF Y–Ba–Cu–O TYPE COMPOUNDS IN THE MODEL OF STRONG ELECTRON–PHONON COUPLING

International Journal of Modern Physics B ◽

10.1142/s0217979288000652 ◽

1988 ◽

Vol 02 (05) ◽

pp. 837-845 ◽

Cited By ~ 2

Author(s):

A. A. Golubov

Keyword(s):

Numerical Solutions ◽

Low Frequency ◽

Thermodynamic Characteristics ◽

Coupling Model ◽

Phonon Coupling ◽

Eliashberg Equations ◽

Phonon Modes ◽

Strong Electron ◽

Phonon Spectra ◽

Electron Phonon Coupling

Based on recently measured phonon density of states of Y–Ba–Cu–O an investigation of the strong electron-phonon coupling model is carried out. The numerical solutions of the real axis Eliashberg equations are obtained for a number of phonon spectra parameters. Isotope shifts of T c , spectral behavior of the pairing energy Δ(ω) and the ratio 2Δ g / T c (where Δ g is the gap edge) are calculated. The model gives a very small oxygen isotope shift for rather moderate values of the electron-phonon coupling constant λ ~ 3. The results strongly suggest the weak coupling with high frequency phonon modes and strong coupling with low frequency modes.

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Experimental evidence for strong electron-phonon coupling to selected phonon modes in point-contact spectroscopy of YBa2Cu3O7−δ

Physica C Superconductivity ◽

10.1016/0921-4534(95)00343-6 ◽

1995 ◽

Vol 250 (1-2) ◽

pp. 59-66 ◽

Cited By ~ 20

Author(s):

Y. Yagil ◽

N. Hass ◽

G. Desgardin ◽

I. Monot

Keyword(s):

Experimental Evidence ◽

Point Contact ◽

Phonon Coupling ◽

Phonon Modes ◽

Strong Electron ◽

Point Contact Spectroscopy ◽

Electron Phonon Coupling

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Structural phase transition and superconductivity hierarchy in 1T-TaS2 under pressure up to 100 GPa

npj Quantum Materials ◽

10.1038/s41535-021-00320-x ◽

2021 ◽

Vol 6 (1) ◽

Author(s):

Qing Dong ◽

Quanjun Li ◽

Shujia Li ◽

Xuhan Shi ◽

Shifeng Niu ◽

...

Keyword(s):

Structural Phase ◽

Transition Metal Dichalcogenides ◽

Phonon Coupling ◽

Structural Phase Transitions ◽

Strong Electron ◽

Electron Phonon Coupling ◽

Increasing Trend ◽

Metal Dichalcogenides ◽

Dome Shape ◽

Enhanced Superconductivity

AbstractThe adoption of high pressure not only reinforces the comprehension of the structure and exotic electronic states of transition metal dichalcogenides (TMDs) but also promotes the discovery of intriguing phenomena. Here, 1T-TaS2 was investigated up to 100 GPa, and re-enhanced superconductivity was found with structural phase transitions. The discovered I4/mmm TaS2 presents strong electron–phonon coupling, revealing a good superconductivity of the nonlayered structure. The P–T phase diagram shows a dome shape centered at ~20 GPa, which is attributed to the distortion of the 1T structure. Accompanied by the transition to nonlayered structure above 44.5 GPa, the superconducting critical temperature shows an increasing trend and reaches ~7 K at the highest studied pressure, presenting superior superconductivity compared to the original layered structure. It is unexpected that the pressure-induced re-enhanced superconductivity was observed in TMDs, and the transition from a superconductor with complicated electron-pairing mechanism to a phonon-mediated superconductor would expand the field of pressure-modified superconductivity.

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Resonance and antiresonance in Raman scattering in GaSe and InSe crystals

Scientific Reports ◽

10.1038/s41598-020-79411-x ◽

2021 ◽

Vol 11 (1) ◽

Author(s):

M. Osiekowicz ◽

D. Staszczuk ◽

K. Olkowska-Pucko ◽

Ł. Kipczak ◽

M. Grzeszczyk ◽

...

Keyword(s):

Raman Scattering ◽

Temperature Effect ◽

Band Gap ◽

Raman Spectra ◽

Quantum Interference ◽

Optical Band Gap ◽

Phonon Coupling ◽

Phonon Modes ◽

Electron Phonon Coupling ◽

Resonant Raman

AbstractThe temperature effect on the Raman scattering efficiency is investigated in $$\varepsilon$$ ε -GaSe and $$\gamma$$ γ -InSe crystals. We found that varying the temperature over a broad range from 5 to 350 K permits to achieve both the resonant conditions and the antiresonance behaviour in Raman scattering of the studied materials. The resonant conditions of Raman scattering are observed at about 270 K under the 1.96 eV excitation for GaSe due to the energy proximity of the optical band gap. In the case of InSe, the resonant Raman spectra are apparent at about 50 and 270 K under correspondingly the 2.41 eV and 2.54 eV excitations as a result of the energy proximity of the so-called B transition. Interestingly, the observed resonances for both materials are followed by an antiresonance behaviour noticeable at higher temperatures than the detected resonances. The significant variations of phonon-modes intensities can be explained in terms of electron-phonon coupling and quantum interference of contributions from different points of the Brillouin zone.

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Direct observation of excitonic instability in Ta2NiSe5

Nature Communications ◽

10.1038/s41467-021-22133-z ◽

2021 ◽

Vol 12 (1) ◽

Author(s):

Kwangrae Kim ◽

Hoon Kim ◽

Jonghwan Kim ◽

Changil Kwon ◽

Jun Sung Kim ◽

...

Keyword(s):

Phase Transition ◽

Direct Observation ◽

Structural Phase ◽

Temperature Phase ◽

Phonon Coupling ◽

Strong Electron ◽

Weiss Temperature ◽

Excitonic Insulator ◽

Electron Phonon Coupling ◽

Low Temperature Phase

AbstractCoulomb attraction between electrons and holes in a narrow-gap semiconductor or a semimetal is predicted to lead to an elusive phase of matter dubbed excitonic insulator. However, direct observation of such electronic instability remains extremely rare. Here, we report the observation of incipient divergence in the static excitonic susceptibility of the candidate material Ta2NiSe5 using Raman spectroscopy. Critical fluctuations of the excitonic order parameter give rise to quasi-elastic scattering of B2g symmetry, whose intensity grows inversely with temperature toward the Weiss temperature of TW ≈ 237 K, which is arrested by a structural phase transition driven by an acoustic phonon of the same symmetry at TC = 325 K. Concurrently, a B2g optical phonon becomes heavily damped to the extent that its trace is almost invisible around TC, which manifests a strong electron-phonon coupling that has obscured the identification of the low-temperature phase as an excitonic insulator for more than a decade. Our results unambiguously reveal the electronic origin of the phase transition.

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