scholarly journals Magnetophonons & type-B Goldstones from hydrodynamics to holography

2020 ◽  
Vol 2020 (9) ◽  
Author(s):  
Matteo Baggioli ◽  
Sebastian Grieninger ◽  
Li Li
Keyword(s):  
Magnetic Field ◽  
2D Materials ◽  
Goldstone Boson ◽  
Quasinormal Modes ◽  
Effective Field ◽  
Zero Magnetic Field ◽  
Type B ◽  
Hydrodynamic Modes ◽  
Pinning Mechanism ◽  
The Magnetic Field

Abstract We perform a detailed analysis of a large class of effective holographic models with broken translations at finite charge density and magnetic field. We exhaustively discuss the dispersion relations of the hydrodynamic modes at zero magnetic field and successfully match them to the predictions from charged hydrodynamics. At finite magnetic field, we identify the presence of an expected type-B Goldstone boson Re[ω] ∼ k2, known as magnetophonon and its gapped partner — the magnetoplasmon. We discuss their properties in relation to the effective field theory and hydrodynamics expectations. Finally, we compute the optical conductivities and the quasinormal modes at finite magnetic field. We observe that the pinning frequency of the magneto-resonance peak increases with the magnetic field, in agreement with experimental data on certain 2D materials, revealing the quantum nature of the holographic pinning mechanism.

Effects of the magnetic field gradient on the wall power deposition of Hall thrusters

2017 ◽  
Vol 83 (2) ◽  
Author(s):  
Yongjie Ding ◽  
Peng Li ◽  
Xu Zhang ◽  
Liqiu Wei ◽  
Hezhi Sun ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Field Gradient ◽  
Discharge Channel ◽  
Magnetic Field Gradient ◽  
Zero Magnetic Field ◽  
Power Deposition ◽  
Neutral Gas ◽  
Channel Exit ◽  
Ionization Region ◽  
The Magnetic Field

The effect of the magnetic field gradient in the discharge channel of a Hall thruster on the ionization of the neutral gas and power deposition on the wall is studied through adopting the 2D-3V particle-in-cell (PIC) and Monte Carlo collisions (MCC) model. The research shows that by gradually increasing the magnetic field gradient while keeping the maximum magnetic intensity at the channel exit and the anode position unchanged, the ionization region moves towards the channel exit and then a second ionization region appears near the anode region. Meanwhile, power deposition on the walls decreases initially and then increases. To avoid power deposition on the walls produced by electrons and ions which are ionized in the second ionization region, the anode position is moved towards the channel exit as the magnetic field gradient is increased; when the anode position remains at the zero magnetic field position, power deposition on the walls decreases, which can effectively reduce the temperature and thermal load of the discharge channel.

scholarly journals ANOMALOUS DEFECTS AND THEIR QUANTIZED TRANSVERSE CONDUCTIVITIES

1998 ◽  
Vol 13 (05) ◽  
pp. 841-861 ◽  
Author(s):  
A. P. BALACHANDRAN ◽  
VARGHESE JOHN ◽  
ARSHAD MOMEN ◽  
FERNANDO MORAES
Keyword(s):  
Magnetic Field ◽  
Field Theory ◽  
Bound States ◽  
Three Dimensional ◽  
External Electromagnetic Field ◽  
Effective Field ◽  
Screw Dislocations ◽  
Dimensional Gravity ◽  
The Magnetic Field ◽  
Conduction Properties

Using a description of defects in solids in terms of three-dimensional gravity, we study the propagation of electrons in the background of disclinations and screw dislocations. We study the situations where there are bound states that are effectively localized on the defect and hence can be described in terms of an effective (1+1)-dimensional field theory for the low energy excitations. In the case of screw dislocations, we find that these excitations are chiral and can be described by an effective field theory of chiral fermions. Fermions of both chirality occur even for a given direction of the magnetic field. The "net" chirality of the system however is not always the same for a given direction of the magnetic field, but changes from one sign of the chirality through zero to the other sign as the Fermi momentum or the magnitude of the magnetic flux is varied. On coupling to an external electromagnetic field, the latter becomes anomalous and predicts novels conduction properties for these material.

Magnetic Prehistory in the Heat Capacity of the Low-Temperature Superconductors

2015 ◽  
Vol 233-234 ◽  
pp. 741-744
Author(s):  
Sergey Mikhailovich Podgornykh
Keyword(s):  
Magnetic Field ◽  
Heat Capacity ◽  
External Magnetic Field ◽  
Low Temperature ◽  
Temperature Dependence ◽  
Zero Magnetic Field ◽  
Zero Field ◽  
Ring Specimen ◽  
Trapped Flux ◽  
The Magnetic Field

Effect of the magnetic prehistory on the temperature dependence of the heat capacity of the superconducting Pb, La, Sn. has been studied. As soon as the external magnetic field riches the valueHext=HCthe superconductivity is completely destroyed. The trapped flux was produced in the ring specimen after the magnetic field was turned off atT<TC. We observed a difference of the value of the heat capacity between zero field cooled (ZFC) and field cooled (FC) states in zero magnetic field for the ring specimen. It is found that the FC heat capacity is smaller than the heat capacity both in the normal and in superconducting states.

scholarly journals ERROR IN MEASURING THE MAGNETIC LIQUID MAGNETIZATION BY THE NUCLEAR MAGNETIC RESONANCE, CAUSED BY THE UNCERTAINTY OF THE EFFECTIVE FIELD CONSTANT

2021 ◽  
Vol 57 ◽  
pp. 15-18
Author(s):  
Alexander I. Zhernovoy ◽  
◽  
Ilya A. Yakimenko ◽  
Keyword(s):  
Magnetic Field ◽  
Nuclear Magnetic Resonance ◽  
Magnetic Resonance ◽  
Field Strength ◽  
Magnetic Field Strength ◽  
Effective Field ◽  
Magnetic Liquid ◽  
Different Shapes ◽  
The Difference ◽  
The Magnetic Field

The magnetic liquid magnetization is usually determined by measuring the magnetic field strength, which linearly depends on the effective field constant of the liquid and the demagnetization coefficient of the sample. The article proposes to measure the magnetic field strength, generated by the same magnetic liquid in the samples of different shapes, and to determine the magnetization relying on the difference in strength, generated by the samples of various shapes, taking advantage of the fact that the effective field constant does not depend on the shape of the sample

scholarly journals Молекулярные состояния композитных фермионов в самоорганизованных квантовых точках InP/GaInP в нулевом внешнем магнитном поле

2020 ◽  
Vol 54 (2) ◽  
pp. 138
Author(s):  
А.М. Минтаиров
Keyword(s):  
Magnetic Field ◽  
Quantum Dots ◽  
Near Field ◽  
Optical Microscope ◽  
Zero Magnetic Field ◽  
Composite Fermions ◽  
Photoluminescence Spectra ◽  
Topological Quantum ◽  
Near Field Scanning ◽  
The Magnetic Field

Abstract The size and positions of regions of line localization and the magnetic-field (0–10 T) dependence of the low-temperature (10 K) photoluminescence spectra of single InP/GaInP quantum dots with a number of electrons of N = 5–7 and a Wigner–Seitz radius of ~2.5 are determined using a near-field scanning optical microscope. The formation of composite fermion molecules with a size coinciding with that of localization regions and bond lengths of ~30 and 50 nm, respectively, at a Landau-level filling factor from 1/2 to 2/7 in zero magnetic field is established. At N = 6, the pairing and rearrangement of composite fermions under photoexcitation are found, which offers opportunities for the use of InP/GaInP quantum dots to create a magnetic-field-free topological quantum gate.

scholarly journals Non-local terahertz photoconductivity in the topological phase of Hg1−xCdxTe

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
A. S. Kazakov ◽  
A. V. Galeeva ◽  
A. I. Artamkin ◽  
A. V. Ikonnikov ◽  
L. I. Ryabova ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Laser Pulses ◽  
Zero Magnetic Field ◽  
Zero Field ◽  
Topological Phase ◽  
Non Local ◽  
Dark Signal ◽  
The Magnetic Field

AbstractWe report on observation of strong non-local photoconducitivity induced by terahertz laser pulses in non-zero magnetic field in heterostructures based on Hg1−xCdxTe films being in the topological phase. While the zero-field non-local photoconductivity is negligible, it is strongly enhanced in magnetic fields ~ 0.05 T resulting in appearance of an edge photocurrent that exceeds the respective dark signal by orders of magnitude. This photocurrent is chiral, and the chirality changes every time the magnetic field or the electric bias is reversed. Appearance of the non-local terahertz photoconductivity is attributed to features of the interface between the topological film and the trivial buffer.

scholarly journals Chiral phase transition of three flavor QCD with nonzero magnetic field using standard staggered fermions

2018 ◽  
Vol 175 ◽  
pp. 07041 ◽  
Author(s):  
Akio Tomiya ◽  
Heng-Tong Ding ◽  
Swagato Mukherjee ◽  
Christian Schmidt ◽  
Xiao-Dan Wang
Keyword(s):  
Magnetic Field ◽  
Phase Transition ◽  
Quark Mass ◽  
Chiral Condensate ◽  
Zero Magnetic Field ◽  
Chiral Phase ◽  
Chiral Phase Transition ◽  
Magnetic Catalysis ◽  
Staggered Fermions ◽  
The Magnetic Field

Lattice simulations for (2+1)-flavor QCD with external magnetic field demon-strated that the quark mass is one of the important parameters responsible for the (inverse) magnetic catalysis. We discuss the dependences of chiral condensates and susceptibilities, the Polyakov loop on the magnetic field and quark mass in three degenerate flavor QCD. The lattice simulations are performed using standard staggered fermions and the plaquette action with spatial sizes Nσ = 16 and 24 and a fixed temporal size Nτ = 4. The value of the quark masses are chosen such that the system undergoes a first order chiral phase transition and crossover with zero magnetic field. We find that in light mass regime, the quark chiral condensate undergoes magnetic catalysis in the whole temperature region and the phase transition tend to become stronger as the magnetic field increases. In crossover regime, deconfinement transition temperature is shifted by the magnetic field when quark mass ma is less than 0:4. The lattice cutoff effects are also discussed.

scholarly journals Incoherent hydrodynamics of density waves in magnetic fields

2021 ◽  
Vol 2021 (5) ◽  
Author(s):  
Aristomenis Donos ◽  
Christiana Pantelidou ◽  
Vaios Ziogas
Keyword(s):  
Magnetic Field ◽  
Optical Properties ◽  
Finite Temperature ◽  
Chemical Potential ◽  
Density Wave ◽  
Density Waves ◽  
Hydrodynamic Modes ◽  
Momentum Relaxation ◽  
Effective Theories ◽  
The Magnetic Field

Abstract We use holography to derive effective theories of fluctuations in spontaneously broken phases of systems with finite temperature, chemical potential, magnetic field and momentum relaxation in which the order parameters break translations. We analytically construct the hydrodynamic modes corresponding to the coupled thermoelectric and density wave fluctuations and all of them turn out to be purely diffusive for our system. Upon introducing pinning for the density waves, some of these modes acquire not only a gap, but also a finite resonance due to the magnetic field. Finally, we study the optical properties and perform numerical checks of our analytical results. A crucial byproduct of our analysis is the identification of the correct current which describes the transport of heat in our system.

A Nonintrusive Method of Measuring the Local Mechanical Properties of Soft Hydrogels Using Magnetic Microneedles

2008 ◽  
Vol 131 (2) ◽  
Author(s):  
Uday Chippada ◽  
Bernard Yurke ◽  
Penelope C. Georges ◽  
Noshir A. Langrana
Keyword(s):  
Magnetic Field ◽  
Mechanical Properties ◽  
Field Gradient ◽  
Type I Collagen ◽  
Zero Magnetic Field ◽  
Arbitrary Field ◽  
Type I ◽  
Collagen Gels ◽  
Field Gradients ◽  
The Magnetic Field

Soft hydrogels serving as substrates for cell attachment are used to culture many types of cells. The mechanical properties of these gels influence cell morphology, growth, and differentiation. For studies of cell growth on inhomogeneous gels, techniques by which the mechanical properties of the substrate can be measured within the proximity of a given cell are of interest. We describe an apparatus that allows the determination of local gel elasticity by measuring the response of embedded micron-sized magnetic needles to applied magnetic fields. This microscope-based four-magnet apparatus can apply both force and torque on the microneedles. The force and the torque are manipulated by changing the values of the magnetic field at the four poles of the magnet using a feedback circuit driven by LABVIEW. Using Hall probes, we have mapped out the magnetic field and field gradients produced by each pole when all the other poles are held at zero magnetic field. We have verified that superposition of these field maps allows one to obtain field maps for the case when the poles are held at arbitrary field values. This allows one to apply known fields and field gradients to a given microneedle. An imaging system is employed to measure the displacement and rotation of the needles. Polyacrylamide hydrogels of known elasticity were used to determine the relationship between the field gradient at the location of the needles and the force acting on the needles. This relationship allows the force on the microneedle to be determined from a known field gradient. This together with a measurement of the displacement of the needle in a given gel allows one to determine the stiffness (F∕δ) of the gel and the elastic modulus, provided Poison’s ratio is known. Using this method, the stiffness and the modulus of elasticity of type-I collagen gels were found to be 2.64±0.05nN∕μm and 284.6±5.9Pa, respectively. This apparatus is presently being employed to track the mechanical stiffness of the DNA-cross-linked hydrogels, developed by our group, whose mechanical properties can be varied on demand by adding or removing cross-linker strands. Thus a system that can be utilized to track the local properties of soft media as a function of time with minimum mechanical disturbance in the presence of cells is presented.

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