Observing light-induced Floquet band gaps in the longitudinal conductivity of graphene

AbstractFloquet engineering presents a versatile method of dynamically controlling material properties. The light-induced Floquet-Bloch bands of graphene feature band gaps, which have not yet been observed directly. We propose optical longitudinal conductivity as a realistic observable to detect light-induced Floquet band gaps in graphene. These gaps manifest as resonant features in the conductivity, when resolved with respect to the probing frequency and the driving field strength. The electron distribution follows the light-induced Floquet-Bloch bands, resulting in a natural interpretation as occupations of these bands. Furthermore, we show that there are population inversions of the Floquet-Bloch bands at the band gaps for sufficiently strong driving field strengths. This strongly reduces the conductivity at the corresponding frequencies. Therefore our proposal puts forth not only an unambiguous demonstration of light-induced Floquet-Bloch bands, which advances the field of Floquet engineering in solids, but also points out the control of transport properties via light, that derives from the electron distribution on these bands.

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On the Validity of the Two-term Approximation of the Electron Distribution Function

Australian Journal of Physics ◽

10.1071/ph710835 ◽

1971 ◽

Vol 24 (4) ◽

pp. 835 ◽

Cited By ~ 13

Author(s):

RE Robson ◽

Kailash Kumar

Keyword(s):

Distribution Function ◽

Field Strength ◽

Drift Velocity ◽

Electron Distribution ◽

Electron Distribution Function ◽

Polynomial Expansion ◽

Neutral Gas ◽

Low Field ◽

Term Approximation ◽

Field Strengths

The Boltzmann equation for electrons moving in a neutral gas under the influence of an externally applied field is solved by expanding the electron distribution function in terms of Legendre and Sonine polynomials. The solution is given in terms of infinite matrices which have elements ordered by the Sonine polynomial index, and which are dependent upon the field strength. From the structure of the formulae, it is possible to infer that truncation of the Legendre polynomial expansion after two terms is a good approximation at all field strengths. This is supported by calculations of the electron drift velocity at low field strengths, which show that the error introduced by making the two-term approximation is small, even when the deviation from equilibrium is significant. The convergence of the Sonine polynomial expansion is shown to be strongly depende:r;J.t upon field strength, and large matrices are required in the drift velocity formula at even small field strengths.

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Interpreting equilibrium-conductivity and conductivity-relaxation measurements to establish thermodynamic and transport properties for multiple charged defect conducting ceramics

Faraday Discussions ◽

10.1039/c5fd00012b ◽

2015 ◽

Vol 182 ◽

pp. 49-74 ◽

Cited By ~ 34

Author(s):

Huayang Zhu ◽

Sandrine Ricote ◽

W. Grover Coors ◽

Robert J. Kee

Keyword(s):

Transport Properties ◽

Material Properties ◽

Ceramic Materials ◽

Barium Zirconate ◽

Charged Defect ◽

Conductivity Measurements ◽

Conductivity Relaxation ◽

Kinetics Parameters ◽

Relaxation Measurements ◽

Thermodynamic And Transport Properties

A model-based interpretation of measured equilibrium conductivity and conductivity relaxation is developed to establish thermodynamic, transport, and kinetics parameters for multiple charged defect conducting (MCDC) ceramic materials. The present study focuses on 10% yttrium-doped barium zirconate (BZY10). In principle, using the Nernst–Einstein relationship, equilibrium conductivity measurements are sufficient to establish thermodynamic and transport properties. However, in practice it is difficult to establish unique sets of properties using equilibrium conductivity alone. Combining equilibrium and conductivity-relaxation measurements serves to significantly improve the quantitative fidelity of the derived material properties. The models are developed using a Nernst–Planck–Poisson (NPP) formulation, which enables the quantitative representation of conductivity relaxations caused by very large changes in oxygen partial pressure.

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Investigation of the cosmic ray population and magnetic field strength in the halo of NGC 891

Astronomy and Astrophysics ◽

10.1051/0004-6361/201832837 ◽

2018 ◽

Vol 615 ◽

pp. A98 ◽

Cited By ~ 15

Author(s):

D. D. Mulcahy ◽

A. Horneffer ◽

R. Beck ◽

M. Krause ◽

P. Schmidt ◽

...

Keyword(s):

Magnetic Field ◽

Field Strength ◽

Magnetic Field Strength ◽

Low Frequency ◽

Cosmic Ray ◽

Radio Continuum ◽

Continuum Emission ◽

Low Frequencies ◽

Very Large Array ◽

Field Strengths

Context. Cosmic rays and magnetic fields play an important role for the formation and dynamics of gaseous halos of galaxies. Aims. Low-frequency radio continuum observations of edge-on galaxies are ideal to study cosmic-ray electrons (CREs) in halos via radio synchrotron emission and to measure magnetic field strengths. Spectral information can be used to test models of CRE propagation. Free–free absorption by ionized gas at low frequencies allows us to investigate the properties of the warm ionized medium in the disk. Methods. We obtained new observations of the edge-on spiral galaxy NGC 891 at 129–163 MHz with the LOw Frequency ARray (LOFAR) and at 13–18 GHz with the Arcminute Microkelvin Imager (AMI) and combine them with recent high-resolution Very Large Array (VLA) observations at 1–2 GHz, enabling us to study the radio continuum emission over two orders of magnitude in frequency. Results. The spectrum of the integrated nonthermal flux density can be fitted by a power law with a spectral steepening towards higher frequencies or by a curved polynomial. Spectral flattening at low frequencies due to free–free absorption is detected in star-forming regions of the disk. The mean magnetic field strength in the halo is 7 ± 2 μG. The scale heights of the nonthermal halo emission at 146 MHz are larger than those at 1.5 GHz everywhere, with a mean ratio of 1.7 ± 0.3, indicating that spectral ageing of CREs is important and that diffusive propagation dominates. The halo scale heights at 146 MHz decrease with increasing magnetic field strengths which is a signature of dominating synchrotron losses of CREs. On the other hand, the spectral index between 146 MHz and 1.5 GHz linearly steepens from the disk to the halo, indicating that advection rather than diffusion is the dominating CRE transport process. This issue calls for refined modelling of CRE propagation. Conclusions. Free–free absorption is probably important at and below about 150 MHz in the disks of edge-on galaxies. To reliably separate the thermal and nonthermal emission components, to investigate spectral steepening due to CRE energy losses, and to measure magnetic field strengths in the disk and halo, wide frequency coverage and high spatial resolution are indispensable.

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A 4 × 4 array multichannel magnetic stimulation system using submillimeter sized planar square spiral coils: The spatial distribution of electromagnetic field

International Journal of Applied Electromagnetics and Mechanics ◽

10.3233/jae-210139 ◽

2022 ◽

pp. 1-18

Author(s):

Lei Tian ◽

Limei Song ◽

Yu Zheng ◽

Jinhai Wang

Keyword(s):

Magnetic Field ◽

Electromagnetic Field ◽

Spatial Distribution ◽

Field Strength ◽

Electric Field ◽

Magnetic Stimulation ◽

Spiral Coil ◽

Average Magnetic Field ◽

Stimulation System ◽

Field Strengths

Multi-coil magnetic stimulation has advantages over single-coil magnetic stimulation, such as more accurate targeting and larger stimulation range. In this paper, a 4 × 4 array multichannel magnetic stimulation system based on a submillimeter planar square spiral coil is proposed. The effects of multiple currents with different directions on the electromagnetic field strength and the focusing zone of the array-structured magnetic stimulation system are studied. The spatial distribution characteristics of the electromagnetic field are discussed. In addition, a method is proposed that can predict the spatial distributions of the electric and magnetic fields when currents in different directions are applied to the array-structured magnetic stimulation system. The study results show that in the section of z = 2 μm, the maximum and average magnetic field strengths of the array-structured magnetic stimulation system are 6.39 mT and 2.68 mT, respectively. The maximum and average electric field strengths are 614.7 mV/m and 122.82 mV/m, respectively, where 84.39% of the measured electric field values are greater than 73 mV/m. The average magnetic field strength of the focusing zone, i.e., the zone in between the two coils, is 3.38 mT with a mean square deviation of 0.18. Therefore, the array-structured multi-channel magnetic stimulation system based on a planar square spiral coil can have a small size of 412 μm × 412 μm × 1.7 μm, which helps improving the spatial distribution of electromagnetic field and increase the effectiveness of magnetic stimulation. The main contribution of this paper is a method for designing multichannel micro-magnetic stimulation devices.

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Effect of electromagnetic field on germination of groundnut seeds (Arachis hypogaea L)

South Asian Journal of Experimental Biology ◽

10.38150/sajeb.2(2).p73-78 ◽

2012 ◽

Vol 2 (2) ◽

pp. 73-78

Author(s):

E. Rajasekhar ◽

R. Jeevan Kumar ◽

C. M. Subhan ◽

P. Panduranga ◽

T. Krishnamurthy

Keyword(s):

Electromagnetic Field ◽

Relative Humidity ◽

Field Strength ◽

Arachis Hypogaea ◽

Exposure Time ◽

Room Temperature ◽

Total Weight ◽

South Pole ◽

Arachis Hypogaea L ◽

Field Strengths

Present work is about the influence of Electromagnetic field [EMF] treatment on the improvement of groundnut seeds (Arachis hypogaea L) germination. The treatment consisted of different electromagnetic field strengths 2, 4, 7 and 10 milli Tesla [mT] in different exposure times 10, 20, 30 and 40 min. In every measurement, the relative humidity and room temperature were recorded. The germination [G] of seed in terms of percentage [% ], the stems length [SL] and roots length [RL] in millimeter [mm] at 6th day and 12th day after experiment, and the total weight [TW] in milligram at 12th day have been measured. Best results have been obtained for variants with exposure time of 30 min and field strength of 7 mT at south pole. Result obtained in the present investigation revealed that the energy absorbed by molecules was high at lower output strength and shorter exposure time improved biologicalfunctions, stimulation effect could be achieved.

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Development and studies of Cd1−xMgxTe thin films with varying band gaps to understand the Mg incorporation and the related material properties

Applied Thermal Engineering ◽

10.1016/j.applthermaleng.2016.10.163 ◽

2017 ◽

Vol 114 ◽

pp. 1169-1175 ◽

Cited By ~ 5

Author(s):

Roger C. Palomera ◽

Omar S. Martínez ◽

J. Pantoja-Enriquez ◽

N.R. Mathews ◽

Martín G. Reyes-Banda ◽

...

Keyword(s):

Thin Films ◽

Material Properties ◽

Band Gaps ◽

Related Material

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Programmable shunt valve interactions with osseointegrated hearing devices

Journal of Neurosurgery Pediatrics ◽

10.3171/2016.11.peds16501 ◽

2017 ◽

Vol 19 (4) ◽

pp. 384-390

Author(s):

Matthew J. Pierson ◽

Daniel Wehrmann ◽

J. Andrew Albers ◽

Najib E. El Tecle ◽

Dary Costa ◽

...

Keyword(s):

Magnetic Field ◽

Field Strength ◽

Magnetic Field Strength ◽

Shunt Valve ◽

Vp Shunt ◽

Magnetic Attachment ◽

Hearing Devices ◽

Programmable Valves ◽

The Magnetic Field ◽

Field Strengths

OBJECTIVE Patients with ventriculoperitoneal (VP) shunts with programmable valves who would benefit from osseointegrated hearing devices (OIHDs) represent a unique population. The aim of this study was to evaluate the magnetic field strengths of 4 OIHDs and their interactions with 5 programmable VP shunt valves. METHODS Magnetic field strength was measured as a function of distance for each hearing device (Cochlear Baha 5, Cochlear Baha BP110, Oticon Ponto Plus Power, and Medtronic Sophono) in the following modes: inactive, active in quiet, and active in 60 decibels of background noise in the sound booth. The hearing devices were introduced to each shunt valve (Aesculap proGAV, Aesculap proGAV 2.0, Codman Hakim, Codman Certas, and Medtronic Strata II) also as a function of distance in these identical 3 settings. Each trial was repeated 5 times. Between each trial, the valves were assessed for a change in setting. Finally, using a skull model, the devices were introduced to each other in standard anatomical locations and the valves were assessed for a change in settings. RESULTS The maximum magnetic field strengths generated by the Cochlear Baha 5, BP110, and Oticon OIHDs were 1.1, 36.2, and 48.7 gauss (G), respectively. The maximum strength generated by the Sophono device was > 800 G. The magnetic field strength of the hearing devices decreased markedly with increasing distance from the device. The strength of the Sophono's magnetic attachment decreased to 34.8 G at 5 mm. The Codman Hakim, Codman Certas, and Medtronic Strata II valve settings changed when rotating the valves next to the Sophono abutment. No other changes in valve settings occurred in the distance or anatomical models for any other trials. CONCLUSIONS This is the first study evaluating the interaction between OIHDs and programmable VP shunt valves. The findings suggest that it is safe to use these devices together without having to switch to a nonprogrammable valve or move the shunt valve to a more distant location. Still, care should be taken if the Sophono device is used to ensure that the valve is ≥ 5 mm away from the magnetic attachment.

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CHARACTERISATION OF THE COMPLEX SHEAR MODULUS PROPERTIES OF ELECTRO-RHEOLOGICAL FLUIDS BY THE DIRECT STIFFNESS AND MASTER CURVE TECHNIQUES

International Journal of Modern Physics B ◽

10.1142/s0217979296001677 ◽

1996 ◽

Vol 10 (23n24) ◽

pp. 3227-3236 ◽

Cited By ~ 3

Author(s):

S O Oyadiji

Keyword(s):

Field Strength ◽

Shear Modulus ◽

Electric Field ◽

Electric Field Strength ◽

Loss Factor ◽

Master Curve ◽

Measured Temperature ◽

Direct Stiffness ◽

Er Fluid ◽

Field Strengths

The direct stiffness technique was employed to characterise the complex modulus properties of a silicone oil-based electrorheological fluid over a frequency range from 30Hz to 300Hz and a temperature range from 0°C to 60ºC. The ER fluid device utilised was a set of concentric cylinders possessing a radial gap of 3mm between adjacent cylinders. Electric field strengths of between 0kV/mm and 2kV/mm were applied across the ER fluid. The results show that the shear modulus of the ER fluid decreased monotonically as the temperature was increased from 0ºC to 60ºC. Overall, the shear modulus decreased by a factor of up to 20. On the other hand, the shear loss factor increased from a low value of about 0.05 at 0ºC to a high value of about 1.0 at 60ºC. Conversely, as the electric field strength was increased from 0kV/mm to 2kV/mm, the shear modulus increased whereas the loss factor decreased. At all temperatures and electric field strengths of these investigations, both the shear modulus and loss factor increased in value as the excitation frequency was increased. The sets of measured temperature- and frequency-dependent data were converted, using the master curve technique, to master curves of shear modulus and loss factor which vary with frequency over several decades at a constant reference temperature and for varying levels of the electric field strength.

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Effect of magnetic field strength on the linewidth and spin-lattice relaxation time of the thiocyanate carbon of cyanylated β-lactoglobulin B: optimization of the experimental parameters for observing thiocyanate carbons in proteins

Biochemical Journal ◽

10.1042/bj3060531 ◽

1995 ◽

Vol 306 (2) ◽

pp. 531-535

Author(s):

J P G Malthouse ◽

P Phelan

Keyword(s):

Magnetic Field ◽

Field Strength ◽

Magnetic Field Strength ◽

Chemical Shift Anisotropy ◽

Relaxation Times ◽

Lattice Relaxation ◽

Spin Lattice Relaxation ◽

Spin Lattice Relaxation Time ◽

Spin Lattice ◽

Field Strengths

The linewidths and spin-lattice relaxation times of the 13C-n.m.r. signal at 109.7 p.p.m. due to the thiocyanate carbon of intact [cyanato-13C]cyanylated-beta-lactoglobulin-B have been determined at magnetic field strengths of 1.88, 6.34 and 11.74 T as well as the spin-lattice relaxation times of its backbone alpha-carbon atoms. The linewidths were directly proportional to the square of the magnetic field strength and we conclude that, at magnetic field strengths of 6.34 T or above, more than 70% of the linewidth will be determined by chemical-shift anisotropy. We estimate that the spin-lattice relaxation time resulting from the chemical-shift anisotropy of the thiocyanate carbon is 1.52 +/- 0.1 s and we conclude that for magnetic field strengths of 6.34 T and above the observed spin-lattice relaxation time of the thiocyanate carbon will be essentially independent of magnetic field strength. Using the rigid-rotor model we obtain estimates of the rotational correlation time of [cyanato-13C]cyanylated-beta-lactoglobulin-B and of the chemical-shift anisotropy shielding tensor of its thiocyanate carbon. We have calculated the linewidths and spin-lattice relaxation times of thiocyanate carbons at magnetic field strengths of 1.88-14.1 T in proteins with M(r) values in the range 10,000-400,000. The effects of magnetic field strength on the resolution and signal-to-noise ratios of the signals due to thiocyanate carbons attached to proteins of M(r) greater than 10,000 are discussed.

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