scholarly journals Low energy electrodynamics of CrI3 layered ferromagnet

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Luca Tomarchio ◽  
Salvatore Macis ◽  
Lorenzo Mosesso ◽  
Loi T. Nguyen ◽  
Antonio Grilli ◽  
...  
Keyword(s):  
Optical Properties ◽  
Degrees Of Freedom ◽  
Near Infrared ◽  
Effective Interaction ◽  
Blue Shift ◽  
Ferromagnetic Phase ◽  
Phonon Modes ◽  
Strong Electron ◽  
Spin Lattice ◽  
Electron Phonon Interaction

AbstractWe report on the optical properties from terahertz (THz) to Near-Infrared (NIR) of the layered magnetic compound CrI3 at various temperatures, both in the paramagnetic and ferromagnetic phase. In the NIR spectral range, we observe an insulating electronic gap around 1.1 eV which strongly hardens with decreasing temperature. The blue shift observed represents a record in insulating materials and it is a fingerprint of a strong electron-phonon interaction. Moreover, a further gap hardening is observed below the Curie temperature, indicating the establishment of an effective interaction between electrons and magnetic degrees of freedom in the ferromagnetic phase. Similar interactions are confirmed by the disappearance of some phonon modes in the same phase, as expected from a spin-lattice interaction theory. Therefore, the optical properties of CrI3 reveal a complex interaction among electronic, phononic and magnetic degrees of freedom, opening many possibilities for its use in 2-Dimensional heterostructures.

scholarly journals Low Energy Electrodynamics of CrI3 Layered Ferromagnet

2021 ◽  
Author(s):  
Luca Tomarchio ◽  
Salvatore Macis ◽  
Lorenzo Mosesso ◽  
Loi T. Nguyen ◽  
Antonio Grilli ◽  
...  
Keyword(s):  
Optical Properties ◽  
Degrees Of Freedom ◽  
Near Infrared ◽  
Effective Interaction ◽  
Blue Shift ◽  
Ferromagnetic Phase ◽  
Phonon Modes ◽  
Strong Electron ◽  
Spin Lattice ◽  
Electron Phonon Interaction

Abstract We report on the optical properties from terahertz (THz) to Near-Infrared (NIR) of the layered magnetic compound CrI3 at various temperatures, both in the para- magnetic and ferromagnetic phase. In the NIR spectral range, we have observed an insulating electronic gap around 1.1 eV which strongly hardens with decreasing temperature. The blue shift observed represents a record in insulating materials and it is a fingerprint of a strong electron-phonon interaction. Moreover, a further gap hardening is observed below the Curie temperature, indicating the establishment of an effective interaction between electrons and magnetic degrees of freedom in the ferromagnetic phase. This interaction is confirmed by the disappearance of some phonon modes in the same phase as expected from a spin-lattice interaction theory. Therefore, the optical properties of CrI3 reveal a complex interaction among electronic, phononic and magnetic degrees of freedom, opening many possibilities for its use in 2-Dimensional heterostructures.

Optical Properties of Near-Infrared Cyanine Dye Molecules Adsorbed on Silver Nanoparticles

2012 ◽  
Vol 457-458 ◽  
pp. 1250-1253
Author(s):  
Tao Meng ◽  
Chun Mei Zhang ◽  
Mi Dan Li ◽  
Chun Liu ◽  
Shan Shan Meng
Keyword(s):  
Silver Nanoparticles ◽  
Optical Properties ◽  
Optical Property ◽  
Silver Nanoparticle ◽  
Near Infrared ◽  
Blue Shift ◽  
Cyanine Dye ◽  
Dye Molecules ◽  
Near Ir ◽  
Spectral Peaks

The optical property of near-infrared cyanine dye adsorbed on silver nanopaticals has been studied by means of UV-Vis spectrophotometer. The adsorption of near-IR cyanine dye on silver nanopaticles was highly dependent on the concentration of silver nanoparticles. As a result, in the UV-Vis spectra, it was shown that the “red-shift”, as silver nanoparticles size, increased and the “blue-shift”, as concentration of silver nanoparticle increased as well. The adsorbed spectral peaks of near-infrared cyanine dye disappeared as concentration of silver nanoparticles increased.

Synthesis and Characterization of SnS Nanoparticles through a Non-Aqueous Chemical Route for Depositing Photovoltaic Absorber Layers

2014 ◽  
Vol 28 ◽  
pp. 91-99 ◽  
Author(s):  
Mou Pal ◽  
A. Martinez Ayala ◽  
N.R. Mathews ◽  
X. Mathew
Keyword(s):  
Optical Properties ◽  
Chemical Composition ◽  
Near Infrared ◽  
Blue Shift ◽  
Xrd Analysis ◽  
Optical Absorption Spectroscopy ◽  
Complexing Agent ◽  
Chemical Route ◽  
X Ray ◽  
Glass Substrates

SnS nanocrystals of sub-10 nm in size were synthesized by a room temperature, non-aqueous chemical route in the presence of different amounts of triethanolamine (TEA) used as a complexing agent. The crystallinity, size, morphology, chemical composition and optical properties of the as-prepared SnS nanoparticles were investigated by powder X-ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM), Energy-dispersive X-ray spectroscopy (EDS), micro Raman and optical absorption spectroscopy. The XRD analysis and HRTEM investigation of SnS nanoparticles confirmed the presence of crystalline orthorhombic SnS phase. Upon increasing the amount of TEA, the crystallite size of the samples decreased gradually showing evidence of quantum confinement. EDS analysis showed that SnS nanoparticles (NPs) grown in absence of TEA were highly stoichiometric whereas in TEA capped samples, the atomic concentration of S is slightly higher than that of Sn. As-synthesized SnS nanocrystals displayed strong absorption in the visible and near-infrared spectral regions followed by a blue shift of their absorption edge on increasing the TEA concentration. These nanoparticles were used to prepare SnS paste which was deposited on conducting glass substrates to obtain thin films for photovoltaic applications. The crystallinity, morphology, chemical composition and optical properties of annealed SnS films were investigated.

Mechanisms

2021 ◽  
pp. 32-125
Author(s):  
Vladimir Z. Kresin ◽  
Sergei G. Ovchinnikov ◽  
Stuart A. Wolf
Keyword(s):  
Superconducting State ◽  
Degrees Of Freedom ◽  
Pair Correlation ◽  
Three Dimensional ◽  
Layered Materials ◽  
Spin Fluctuations ◽  
Strong Electron ◽  
Hubbard Hamiltonian ◽  
Electron Phonon Interaction ◽  
Phonon Mechanism

This chapter introduces the general concepts of pair correlation, and superconductivity as a strong non-adiabatic phenomenon. Phonon, electronic, and magnetic mechanisms play the major roles; each of them can serve as the origin of the superconducting state. Speaking of the phonon mechanism, it is essential that an explicit expression for Tc depend on the intensity of the electron–phonon interaction. In principle, the electron–phonon mechanism can provide high values of Tc, up to room temperature. Pioneering work by Little, who introduced the electronic mechanism, is described. The mechanism has been analysed for one-dimensional, two-dimensional, and three-dimensional systems. The plasmon mechanism can play a role for layered materials. The superconducting state can be provided by magnetic degrees of freedom. The band limit with spin fluctuations and the regime of strong electron correlations are described. The Hubbard Hamiltonian and the t − J model are the ingredients of the approach.

Preparation and Optical Properties of Spherical Bi2S3 Nanoparticles by In Situ Thermal Sulfuration Method

NANO ◽  
2015 ◽  
Vol 10 (02) ◽  
pp. 1550021 ◽  
Author(s):  
Zhankui Cui ◽  
Senlin Li ◽  
Junqiang Zhou ◽  
Jianli Zhang ◽  
Suxiang Ge ◽  
...  
Keyword(s):  
Optical Properties ◽  
Near Infrared ◽  
Light Emission ◽  
Spherical Shape ◽  
Blue Shift ◽  
X Ray ◽  
Quantum Size ◽  
Ft Ir ◽  
Uv Visible

Spherical Bi 2 S 3 nanoparticles (NPs) were prepared by a facile in situ thermal sulfuration method. Different Bi 2 S 3 samples were obtained by controlling the sulfuration time. The products were characterized by X-ray diffractometer (XRD), scanning electron microscopy (SEM), Raman and Fourier-transform infrared (FT-IR) methods. The optical properties were examined by UV-visible-near-infrared (UV-Vis–NIR) and photoluminescence (PL) techniques. The results show that the phase of the products after sulfuration is pure and the spherical shape of Bi NPs has been successfully transmitted to Bi 2 S 3 samples. The light absorption edges exhibit red shift to 1060 nm while the light emission displays blue shift to 868 nm, compared with the energy bandgap of bulk Bi 2 S 3. The reason for the special optical properties of Bi 2 S 3 NPs by this in situ sulfuration route is considered to associate with the defects and quantum size effect of NPs.

scholarly journals The Effect of Nitrogen Incorporation on the Optical Properties of Si-Rich a-SiCx Films Deposited by VHF PECVD

Micromachines ◽  
2021 ◽  
Vol 12 (6) ◽  
pp. 637
Author(s):  
Hongliang Li ◽  
Zewen Lin ◽  
Yanqing Guo ◽  
Jie Song ◽  
Rui Huang ◽  
...  
Keyword(s):  
Optical Properties ◽  
Near Infrared ◽  
Chemical Vapor ◽  
Wide Bandgap ◽  
Nonradiative Recombination ◽  
Very High Frequency ◽  
N Content ◽  
High Frequency Plasma ◽  
Frequency Plasma ◽  
N Incorporation

The influence of N incorporation on the optical properties of Si-rich a-SiCx films deposited by very high-frequency plasma-enhanced chemical vapor deposition (VHF PECVD) was investigated. The increase in N content in the films was found to cause a remarkable enhancement in photoluminescence (PL). Relative to the sample without N incorporation, the sample incorporated with 33% N showed a 22-fold improvement in PL. As the N content increased, the PL band gradually blueshifted from the near-infrared to the blue region, and the optical bandgap increased from 2.3 eV to 5.0 eV. The enhancement of PL was suggested mainly from the effective passivation of N to the nonradiative recombination centers in the samples. Given the strong PL and wide bandgap of the N incorporated samples, they were used to further design an anti-counterfeiting label.

scholarly journals Imaging the formation and surface phase separation of the CE phase

2021 ◽  
Vol 6 (1) ◽  
Author(s):  
Haibiao Zhou ◽  
Qiyuan Feng ◽  
Yubin Hou ◽  
Masao Nakamura ◽  
Yoshinori Tokura ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Phase Transitions ◽  
Charge Ordering ◽  
Zero Magnetic Field ◽  
Ferromagnetic Phase ◽  
Emergent Properties ◽  
Orbital Ordering ◽  
Strong Electron ◽  
Antiferromagnetic Correlation ◽  
Ordering Transitions

AbstractThe CE phase is an extraordinary phase exhibiting the simultaneous spin, charge, and orbital ordering due to strong electron correlation. It is an ideal platform to investigate the role of the multiple orderings in the phase transitions and discover emergent properties. Here, we use a cryogenic high-field magnetic force microscope to image the phase transitions and properties of the CE phase in a Pr0.5Ca0.5MnO3 thin film. In a high magnetic field, we observed a clear suppression of magnetic susceptibility at the charge-ordering insulator transition temperature (TCOI), whereas, at the Néel temperature (TN), no significant change is observed. This observation favors the scenario of strong antiferromagnetic correlation developed below TCOI but raises questions about the Zener polaron paramagnetic phase picture. Besides, we discoverd a phase-separated surface state in the CE phase regime. Ferromagnetic phase domains residing at the surface already exist in zero magnetic field and show ultra-high magnetic anisotropy. Our results provide microscopic insights into the unconventional spin- and charge-ordering transitions and revealed essential attributes of the CE phase, highlighting unusual behaviors when multiple electronic orderings are involved.

scholarly journals High performing flexible optoelectronic devices using thin films of topological insulator

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Animesh Pandey ◽  
Reena Yadav ◽  
Mandeep Kaur ◽  
Preetam Singh ◽  
Anurag Gupta ◽  
...  
Keyword(s):  
Thin Films ◽  
Optical Properties ◽  
Nonlinear Optical ◽  
Near Infrared ◽  
Optoelectronic Devices ◽  
Nonlinear Optical Properties ◽  
Metallic Surface ◽  
Strong Light ◽  
High Performing ◽  
Decay Times

AbstractTopological insulators (TIs) possess exciting nonlinear optical properties due to presence of metallic surface states with the Dirac fermions and are predicted as a promising material for broadspectral phodotection ranging from UV (ultraviolet) to deep IR (infrared) or terahertz range. The recent experimental reports demonstrating nonlinear optical properties are mostly carried out on non-flexible substrates and there is a huge demand for the fabrication of high performing flexible optoelectronic devices using new exotic materials due to their potential applications in wearable devices, communications, sensors, imaging etc. Here first time we integrate the thin films of TIs (Bi2Te3) with the flexible PET (polyethylene terephthalate) substrate and report the strong light absorption properties in these devices. Owing to small band gap material, evolving bulk and gapless surface state conduction, we observe high responsivity and detectivity at NIR (near infrared) wavelengths (39 A/W, 6.1 × 108 Jones for 1064 nm and 58 A/W, 6.1 × 108 Jones for 1550 nm). TIs based flexible devices show that photocurrent is linearly dependent on the incident laser power and applied bias voltage. Devices also show very fast response and decay times. Thus we believe that the superior optoelectronic properties reported here pave the way for making TIs based flexible optoelectronic devices.

RELATIVISTIC NUCLEAR ENERGY DENSITY FUNCTIONALS

2010 ◽  
Vol 19 (04) ◽  
pp. 548-557 ◽  
Author(s):  
D. VRETENAR ◽  
T. NIKŠIĆ ◽  
P. RING
Keyword(s):  
Energy Density ◽  
Degrees Of Freedom ◽  
Nuclear Energy ◽  
Effective Interaction ◽  
Binding Energies ◽  
Large Set ◽  
Density Functionals ◽  
Heavy Nuclei ◽  
Interaction Terms ◽  
Range Dynamics

A class of relativistic nuclear energy density functionals is explored, in which only nucleon degrees of freedom are explicitly used in the construction of effective interaction terms. Short-distance correlations, as well as intermediate and long-range dynamics, are encoded in the nucleon-density dependence of the strength functionals of an effective interaction Lagrangian. The resulting phenomenological effective interaction, adjusted to experimental binding energies of a large set of axially deformed nuclei, together with a new separable pairing interaction adjusted to reproduce the pairing gap in nuclear matter calculated with the Gogny force, is applied in triaxial relativistic Hartree-Bogoliubov calculations of sequences of heavy nuclei: Th , U , Pu , Cm , Cf , Fm , and No .

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