The Experts below are selected from a list of 30399 Experts worldwide ranked by ideXlab platform
Yong Baek Kim - One of the best experts on this subject based on the ideXlab platform.
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anisotropic density fluctuations plasmons and friedel oscillations in nodal line semimetal
New Journal of Physics, 2016Co-Authors: Junwon Rhim, Yong Baek KimAbstract:Motivated by recent experimental efforts on three-dimensional semimetals, we investigate the static and dynamic density response of the nodal line semimetal by computing the polarizability for both undoped and doped cases. The nodal line semimetal in the absence of doping is characterized by a ring-shape zero energy contour in momentum space, which may be considered as a collection of Dirac points. In the doped case, the Fermi surface has a torus shape and two independent processes of the momentum transfer contribute to the singular features of the polarizability even though we only have a single Fermi surface. In the static limit, there exist two independent singularities in the second derivative of the static polarizability. This results in the highly anisotropic Friedel oscillations which show the angle-dependent algebraic power law and the beat phenomena in the oscillatory electron density near a charged impurity. Furthermore, the dynamical polarizability has two singular lines along and , where ? is the angle between the external momentum and the plane where the nodal ring lies. From the dynamical polarizability, we obtain the plasmon modes in the doped case, which show anisotropic dispersions and angle-dependent Plasma Frequencies. Qualitative differences between the low and high doping regimes are discussed in light of future experiments.
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anisotropic density fluctuations plasmons and friedel oscillations in nodal line semimetal
arXiv: Strongly Correlated Electrons, 2015Co-Authors: Junwon Rhim, Yong Baek KimAbstract:Motivated by recent experimental efforts on three-dimensional semimetals, we investigate the static and dynamic density response of the nodal line semimetal by computing the polarizability for both undoped and doped cases. The nodal line semimetal in the absence of doping is characterized by a ring-shape zero energy contour in momentum space, which may be considered as a collection of Dirac points. In the doped case, the Fermi surface has a torus shape and two independent processes of the momentum transfer contribute to the singular features of the polarizability even though we only have a single Fermi surface. In the static limit, there exist two independent singularities in the second derivative of the static polarizability. This results in the highly anisotropic Friedel oscillations which show the angle-dependent algebraic power law and the beat phenomena in the oscillatory electron density near a charged impurity. Furthermore, the dynamical polarizability has two singular lines along $\hbar\omega = \gamma p$ and $\hbar\omega = \gamma p \sin\eta$, where $\eta$ is the angle between the external momentum $\vec{p}$ and the plane where the nodal ring lies. From the dynamical polarizability, we obtain the plasmon modes in the doped case, which show anisotropic dispersions and angle-dependent Plasma Frequencies. Qualitative differences between the low and high doping regimes are discussed in light of future experiments.
M S Shur - One of the best experts on this subject based on the ideXlab platform.
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graphene based Plasma wave devices for terahertz applications
Applied Physics Letters, 2020Co-Authors: Victor Ryzhii, Taiichi Otsuji, M S ShurAbstract:Unique properties of graphene are combined to enable graphene plasmonic devices that could revolutionize the terahertz (THz) electronic technology. A high value of the carrier mobility allows us to excite resonant Plasma waves. The graphene bipolar nature allows for different mechanisms of Plasma wave excitation. Graphene bilayer and multilayer structures make possible improved THz device configurations. The ability of graphene to form a high quality heterostructure with h-BN, black phosphorus, and other materials systems supports advanced heterostructure devices comprised of the best properties of graphene and other emerging materials. In particular, using black phosphorus compounds for cooling electron–hole Plasma in graphene could dramatically improve the conditions for THz lasing. High optical phonon energy allows for reaching higher Plasma Frequencies that are supported by high sheet carrier densities in graphene. Recent improvements in graphene technology combined with a better understanding of the device physics of graphene THz plasmonics and graphene plasmonic device designs hold promise to make graphene THz plasmonic technology one of the key graphene applications. Commercialization of plasmonic graphene technology is facing the same challenges as other graphene applications, which have difficulties in producing uniform large graphene layers, bilayers, and heterostructures of high quality and making good low resistance stable Ohmic contacts. The time projection for large scale graphene electronic device applications now extends into the 2030s. However, emerging graphene mass production technologies might bring commercial applications of the graphene plasmonic terahertz technology closer.
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Plasma oscillations in high electron mobility transistors with recessed gate
Journal of Applied Physics, 2006Co-Authors: Victor Ryzhii, W Knap, Akira Satou, M S ShurAbstract:We calculate the Plasma oscillation spectrum in high-electron-mobility transistors (HEMTs) with recessed gate having the highly doped caps adjacent to the source and drain contacts and the windows between the caps and the gate. The resonant Plasma Frequencies are found as functions of the lengths of the gate, cap, and window regions, the electron concentration in the transistor channel, and the gate voltage. We demonstrate that the effect of cap region can result in a significant reduction of the resonant Frequencies in comparison with those calculated for simplified HEMT model. This can provide a plausible explanation of the data obtained in recent experimental studies of the detection of terahertz radiation in and its emission from HEMTs.
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Plasma and transit time mechanisms of the terahertz radiation detection in high electron mobility transistors
Semiconductor Science and Technology, 2003Co-Authors: Akira Satou, Victor Ryzhii, I Khmyrova, M S ShurAbstract:We develop a device model for a high-electron-mobility transistor (HEMT) affected by the incoming terahertz radiation. The model takes into account the electron Plasma oscillations in the HEMT channel, tunnelling of electrons from the channel into the gate layer and electron transit-time effects in this layer. It is shown that the excitation of Plasma oscillations accompanied by the delay in the electron propagation across the gate layer and a strong nonlinearity of the tunnelling current can result in significant features of the HEMT high-frequency linear and nonlinear characteristics. We derive a formula for the HEMT gate-to-source/drain admittance. We also calculate the variation of the dc current induced by the terahertz radiation and the HEMT detection responsivity. It is found that the detection responsivity exhibits sharp resonant peaks corresponding to the Frequencies of Plasma oscillations. The resonant Plasma Frequencies and the positions of the admittance and detection responsivity peaks depend on the gate length and the lengths of the contact regions (source-to-gate and gate-to-drain spacings) and can be tuned by the gate voltage. The coincidence of the Plasma and transit-time resonances can lead to a marked sharpening of the responsivity peaks.
Nerea Zabala - One of the best experts on this subject based on the ideXlab platform.
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flickering nanometre scale disorder in a crystal lattice tracked by plasmonic flare light emission
Nature Communications, 2020Co-Authors: Cloudy Carnegie, Mattin Urbieta, Rohit Chikkaraddy, Bart De Nijs, Jack Griffiths, William M Deacon, Marlous Kamp, Nerea ZabalaAbstract:The dynamic restructuring of metal nanoparticle surfaces is known to greatly influence their catalytic, electronic transport, and chemical binding functionalities. Here we show for the first time that non-equilibrium atomic-scale lattice defects can be detected in nanoparticles by purely optical means. These fluctuating states determine interface electronic transport for molecular electronics but because such rearrangements are low energy, measuring their rapid dynamics on single nanostructures by X-rays, electron beams, or tunnelling microscopies, is invasive and damaging. We utilise nano-optics at the sub-5nm scale to reveal rapid (on the millisecond timescale) evolution of defect morphologies on facets of gold nanoparticles on a mirror. Besides dynamic structural information, this highlights fundamental questions about defining bulk Plasma Frequencies for metals probed at the nanoscale.
Victor Ryzhii - One of the best experts on this subject based on the ideXlab platform.
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graphene based Plasma wave devices for terahertz applications
Applied Physics Letters, 2020Co-Authors: Victor Ryzhii, Taiichi Otsuji, M S ShurAbstract:Unique properties of graphene are combined to enable graphene plasmonic devices that could revolutionize the terahertz (THz) electronic technology. A high value of the carrier mobility allows us to excite resonant Plasma waves. The graphene bipolar nature allows for different mechanisms of Plasma wave excitation. Graphene bilayer and multilayer structures make possible improved THz device configurations. The ability of graphene to form a high quality heterostructure with h-BN, black phosphorus, and other materials systems supports advanced heterostructure devices comprised of the best properties of graphene and other emerging materials. In particular, using black phosphorus compounds for cooling electron–hole Plasma in graphene could dramatically improve the conditions for THz lasing. High optical phonon energy allows for reaching higher Plasma Frequencies that are supported by high sheet carrier densities in graphene. Recent improvements in graphene technology combined with a better understanding of the device physics of graphene THz plasmonics and graphene plasmonic device designs hold promise to make graphene THz plasmonic technology one of the key graphene applications. Commercialization of plasmonic graphene technology is facing the same challenges as other graphene applications, which have difficulties in producing uniform large graphene layers, bilayers, and heterostructures of high quality and making good low resistance stable Ohmic contacts. The time projection for large scale graphene electronic device applications now extends into the 2030s. However, emerging graphene mass production technologies might bring commercial applications of the graphene plasmonic terahertz technology closer.
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Plasma oscillations in high electron mobility transistors with recessed gate
Journal of Applied Physics, 2006Co-Authors: Victor Ryzhii, W Knap, Akira Satou, M S ShurAbstract:We calculate the Plasma oscillation spectrum in high-electron-mobility transistors (HEMTs) with recessed gate having the highly doped caps adjacent to the source and drain contacts and the windows between the caps and the gate. The resonant Plasma Frequencies are found as functions of the lengths of the gate, cap, and window regions, the electron concentration in the transistor channel, and the gate voltage. We demonstrate that the effect of cap region can result in a significant reduction of the resonant Frequencies in comparison with those calculated for simplified HEMT model. This can provide a plausible explanation of the data obtained in recent experimental studies of the detection of terahertz radiation in and its emission from HEMTs.
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Plasma and transit time mechanisms of the terahertz radiation detection in high electron mobility transistors
Semiconductor Science and Technology, 2003Co-Authors: Akira Satou, Victor Ryzhii, I Khmyrova, M S ShurAbstract:We develop a device model for a high-electron-mobility transistor (HEMT) affected by the incoming terahertz radiation. The model takes into account the electron Plasma oscillations in the HEMT channel, tunnelling of electrons from the channel into the gate layer and electron transit-time effects in this layer. It is shown that the excitation of Plasma oscillations accompanied by the delay in the electron propagation across the gate layer and a strong nonlinearity of the tunnelling current can result in significant features of the HEMT high-frequency linear and nonlinear characteristics. We derive a formula for the HEMT gate-to-source/drain admittance. We also calculate the variation of the dc current induced by the terahertz radiation and the HEMT detection responsivity. It is found that the detection responsivity exhibits sharp resonant peaks corresponding to the Frequencies of Plasma oscillations. The resonant Plasma Frequencies and the positions of the admittance and detection responsivity peaks depend on the gate length and the lengths of the contact regions (source-to-gate and gate-to-drain spacings) and can be tuned by the gate voltage. The coincidence of the Plasma and transit-time resonances can lead to a marked sharpening of the responsivity peaks.
Junwon Rhim - One of the best experts on this subject based on the ideXlab platform.
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anisotropic density fluctuations plasmons and friedel oscillations in nodal line semimetal
New Journal of Physics, 2016Co-Authors: Junwon Rhim, Yong Baek KimAbstract:Motivated by recent experimental efforts on three-dimensional semimetals, we investigate the static and dynamic density response of the nodal line semimetal by computing the polarizability for both undoped and doped cases. The nodal line semimetal in the absence of doping is characterized by a ring-shape zero energy contour in momentum space, which may be considered as a collection of Dirac points. In the doped case, the Fermi surface has a torus shape and two independent processes of the momentum transfer contribute to the singular features of the polarizability even though we only have a single Fermi surface. In the static limit, there exist two independent singularities in the second derivative of the static polarizability. This results in the highly anisotropic Friedel oscillations which show the angle-dependent algebraic power law and the beat phenomena in the oscillatory electron density near a charged impurity. Furthermore, the dynamical polarizability has two singular lines along and , where ? is the angle between the external momentum and the plane where the nodal ring lies. From the dynamical polarizability, we obtain the plasmon modes in the doped case, which show anisotropic dispersions and angle-dependent Plasma Frequencies. Qualitative differences between the low and high doping regimes are discussed in light of future experiments.
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anisotropic density fluctuations plasmons and friedel oscillations in nodal line semimetal
arXiv: Strongly Correlated Electrons, 2015Co-Authors: Junwon Rhim, Yong Baek KimAbstract:Motivated by recent experimental efforts on three-dimensional semimetals, we investigate the static and dynamic density response of the nodal line semimetal by computing the polarizability for both undoped and doped cases. The nodal line semimetal in the absence of doping is characterized by a ring-shape zero energy contour in momentum space, which may be considered as a collection of Dirac points. In the doped case, the Fermi surface has a torus shape and two independent processes of the momentum transfer contribute to the singular features of the polarizability even though we only have a single Fermi surface. In the static limit, there exist two independent singularities in the second derivative of the static polarizability. This results in the highly anisotropic Friedel oscillations which show the angle-dependent algebraic power law and the beat phenomena in the oscillatory electron density near a charged impurity. Furthermore, the dynamical polarizability has two singular lines along $\hbar\omega = \gamma p$ and $\hbar\omega = \gamma p \sin\eta$, where $\eta$ is the angle between the external momentum $\vec{p}$ and the plane where the nodal ring lies. From the dynamical polarizability, we obtain the plasmon modes in the doped case, which show anisotropic dispersions and angle-dependent Plasma Frequencies. Qualitative differences between the low and high doping regimes are discussed in light of future experiments.