scholarly journals Observation of the polaronic character of excitons in a two-dimensional semiconducting magnet CrI3

2020 ◽  
Vol 11 (1) ◽  
Author(s):  
Wencan Jin ◽  
Hyun Ho Kim ◽  
Zhipeng Ye ◽  
Gaihua Ye ◽  
Laura Rojas ◽  
...  
Keyword(s):  
Magnetic Semiconductors ◽  
Longitudinal Optical ◽  
Longitudinal Optical Phonon ◽  
Two Dimensional ◽  
Phonon Coupling ◽  
Temperature Dependent ◽  
Strong Electron ◽  
Range Magnetic Order ◽  
Electron Phonon Coupling ◽  
Long Range Magnetic Order

Abstract Exciton dynamics can be strongly affected by lattice vibrations through electron-phonon coupling. This is rarely explored in two-dimensional magnetic semiconductors. Focusing on bilayer CrI3, we first show the presence of strong electron-phonon coupling through temperature-dependent photoluminescence and absorption spectroscopy. We then report the observation of periodic broad modes up to the 8th order in Raman spectra, attributed to the polaronic character of excitons. We establish that this polaronic character is dominated by the coupling between the charge-transfer exciton at 1.96 eV and a longitudinal optical phonon at 120.6 cm−1. We further show that the emergence of long-range magnetic order enhances the electron-phonon coupling strength by ~50% and that the transition from layered antiferromagnetic to ferromagnetic order tunes the spectral intensity of the periodic broad modes, suggesting a strong coupling among the lattice, charge and spin in two-dimensional CrI3. Our study opens opportunities for tailoring light-matter interactions in two-dimensional magnetic semiconductors.

Mechanisms of high-Tc superconductivity in low-dimensional materials

1987 ◽  
Vol 2 (6) ◽  
pp. 793-799 ◽  
Author(s):  
Vladimir Z. Kresin
Keyword(s):  
Proximity Effect ◽  
Coherence Length ◽  
Two Dimensional ◽  
Phonon Coupling ◽  
Strong Electron ◽  
High Tc ◽  
Electron Phonon Coupling ◽  
Low Dimensionality ◽  
Low Dimensional ◽  
Low Dimensional Materials

High-Tc superconductivity is due to the action of two mechanisms: (1) plasmon mechanism, i.e., exchange of two-dimensional (2-D) plasmons and (2) strong electron-phonon coupling. The low dimensionality and the small value of the carrier concentration make the plasmon mechanism favorable. The small value of the coherence length leads to a unique opportunity to observe a multigap structure. The proximity effect can be used in order to increase Tc of A-15 compounds.

Exciton–phonon interaction in quasi-two dimensional layered (PEA)2(CsPbBr3)n−1PbBr4 perovskite

Nanoscale ◽  
2019 ◽  
Vol 11 (45) ◽  
pp. 21867-21871 ◽  
Author(s):  
Hao Long ◽  
Xiang Peng ◽  
Jianxun Lu ◽  
Kebin Lin ◽  
Liqiang Xie ◽  
...  
Keyword(s):  
Optical Phonon ◽  
Coupling Strength ◽  
Acoustic Phonon ◽  
Longitudinal Optical ◽  
Longitudinal Optical Phonon ◽  
Two Dimensional ◽  
Phonon Coupling ◽  
Phonon Interaction ◽  
2D Material ◽  
Exciton Coupling

Exciton–phonon interaction in quasi-2D material was investigated. It was shown that longitudinal optical phonon, rather than acoustic phonon-exciton coupling dominated the enhancement of exciton–phonon coupling strength.

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

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.

Effects of spin-phonon coupling on two-dimensional ferromagnetic semiconductors: a case study of iron and ruthenium trihalides

Nanoscale ◽  
2021 ◽  
Author(s):  
Yinqiao Liu ◽  
Qinxi Liu ◽  
Ying Liu ◽  
Xue Jiang ◽  
Xiaoliang Zhang ◽  
...  
Keyword(s):  
Transport Properties ◽  
Data Security ◽  
Thermal Transport ◽  
Magnetic Semiconductors ◽  
Ferromagnetic Semiconductors ◽  
Two Dimensional ◽  
Phonon Coupling ◽  
Thermal Transport Properties

The contributions of spin-phonon coupling (SPC) to spin and thermal transport properties are important in the emerging two-dimensional (2D) magnetic semiconductors and are relevant for the data security and working...

Temperature dependent electron–phonon coupling of Au resolved via lattice dynamics measured with sub-picosecond infrared pulses

2021 ◽  
Vol 129 (19) ◽  
pp. 193104
Author(s):  
John A. Tomko ◽  
Sushant Kumar ◽  
Ravishankar Sundararaman ◽  
Patrick E. Hopkins
Keyword(s):  
Lattice Dynamics ◽  
Phonon Coupling ◽  
Temperature Dependent ◽  
Electron Phonon Coupling

scholarly journals Direct observation of excitonic instability in Ta2NiSe5

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.

Strong electron-phonon coupling at a metal/organic interface: PTCDA/Ag(111)

2002 ◽  
Vol 65 (12) ◽  
Author(s):  
F. S. Tautz ◽  
M. Eremtchenko ◽  
J. A. Schaefer ◽  
M. Sokolowski ◽  
V. Shklover ◽  
...  
Keyword(s):  
Phonon Coupling ◽  
Strong Electron ◽  
Electron Phonon Coupling ◽  
Metal Organic
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