scholarly journals Observation of acoustic spin

2019 ◽  
Vol 6 (4) ◽  
pp. 707-712 ◽  
Author(s):  
Chengzhi Shi ◽  
Rongkuo Zhao ◽  
Yang Long ◽  
Sui Yang ◽  
Yuan Wang ◽  
...  
Keyword(s):  
Wave Propagation ◽  
Angular Momentum ◽  
Acoustic Waves ◽  
Propagation Direction ◽  
Spin Angular Momentum ◽  
Particle Rotation ◽  
Guided Mode ◽  
Pressure Fields ◽  
Metamaterial Waveguide ◽  
Spin Momentum

ABSTRACT Unlike optical waves, acoustic waves in fluids are described by scalar pressure fields, and therefore are considered spinless. Here, we demonstrate experimentally the existence of spin in acoustics. In the interference of two acoustic waves propagating perpendicularly to each other, we observed the spin angular momentum in free space as a result of the rotation of local particle velocity. We successfully measured the acoustic spin, and spin-induced torque acting on a designed lossy acoustic probe that results from absorption of the spin angular momentum. The acoustic spin is also observed in the evanescent field of a guided mode traveling along a metamaterial waveguide. We found spin–momentum locking in acoustic waves whose propagation direction is determined by the sign of spin. The observed acoustic spin could open a new door in acoustics and its applications for the control of wave propagation and particle rotation.

scholarly journals Lateral chirality-sorting optical forces

2015 ◽  
Vol 112 (43) ◽  
pp. 13190-13194 ◽  
Author(s):  
Amaury Hayat ◽  
J. P. Balthasar Mueller ◽  
Federico Capasso
Keyword(s):  
Wave Propagation ◽  
Angular Momentum ◽  
Field Gradient ◽  
Transverse Component ◽  
Evanescent Waves ◽  
Unusual Property ◽  
Optical Forces ◽  
Spin Angular Momentum ◽  
Absolute Strength ◽  
The Absolute

The transverse component of the spin angular momentum of evanescent waves gives rise to lateral optical forces on chiral particles, which have the unusual property of acting in a direction in which there is neither a field gradient nor wave propagation. Because their direction and strength depends on the chiral polarizability of the particle, they act as chirality-sorting and may offer a mechanism for passive chirality spectroscopy. The absolute strength of the forces also substantially exceeds that of other recently predicted sideways optical forces.

scholarly journals Observation of elastic spin with chiral meta-sources

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Weitao Yuan ◽  
Chenwen Yang ◽  
Danmei Zhang ◽  
Yang Long ◽  
Yongdong Pan ◽  
...  
Keyword(s):  
Angular Momentum ◽  
Elastic Wave ◽  
Experimental Observation ◽  
Elastic Waves ◽  
Lamb Wave ◽  
Selective Excitation ◽  
Spin Angular Momentum ◽  
Classical Wave ◽  
Directional Routing ◽  
Spin Momentum

AbstractDirectional routing of one-way classical wave has raised tremendous interests about spin-related phenomena. This sparks specifically the elastic wave study of pseudo-spin in meta-structures to perform robust manipulations. Unlike pseudo-spin in mathematics, the intrinsic spin angular momentum of elastic wave is predicted quite recently which exhibits selective excitation of unidirectional propagation even in conventional solids. However, due to the challenge of building up chiral elastic sources, the experimental observation of intrinsic spin of elastic wave is still missing. Here, we successfully measure the elastic spin in Rayleigh and Lamb modes by adopting elaborately designed chiral meta-sources that excite locally rotating displacement polarization. We observe the unidirectional routing of chiral elastic waves, characterize the different elastic spins along different directions, and demonstrate the spin-momentum locking in broad frequency ranges. We also find the selective one-way Lamb wave carries opposite elastic spin on two plate surfaces in additional to the source chirality.

scholarly journals Surface Plasmon-Polaritons and Transverse Spin Angular Momentum at the Boundary of Hyperbolic Metamaterial with Arbitrary Orientation of the Optical Axis

2017 ◽  
Vol 6 (3) ◽  
pp. 70
Author(s):  
V. Belyi ◽  
S. Kurilkina ◽  
N. Kazak ◽  
V. Agabekov
Keyword(s):  
Angular Momentum ◽  
Optical Axis ◽  
Transverse Spin ◽  
Arbitrary Orientation ◽  
Spin Angular Momentum ◽  
Hyperbolic Metamaterials ◽  
Hyperbolic Metamaterial ◽  
Plasmon Polaritons ◽  
Exciting Wave ◽  
Spin Momentum

The possibility is established and the conditions are found for localization of plasmon-polaritons (PPs) near the boundaries of hyperbolic metamaterials (HMs) of both I and II types with arbitrary orientation of the optical axis. It is grounded that such surface PP has the transverse spin momentum which depends on the wavelength of the exciting wave, the orientation of the optical axis of the hyperbolic metamaterial, and dielectric properties of bordered media.

Introduction of spin torques

2017 ◽  
Author(s):  
T. Kimura
Keyword(s):  
Angular Momentum ◽  
Giant Magnetoresistance ◽  
Spontaneous Magnetization ◽  
Magnetic Domain ◽  
Magnetic Multilayers ◽  
Transfer Effect ◽  
Spin Transfer Torque ◽  
Spin Transfer ◽  
Spin Angular Momentum ◽  
Spin Torques

This chapter discusses the spin-transfer effect, which is described as the transfer of the spin angular momentum between the conduction electrons and the magnetization of the ferromagnet that occurs due to the conservation of the spin angular momentum. L. Berger, who introduced the concept in 1984, considered the exchange interaction between the conduction electron and the localized magnetic moment, and predicted that a magnetic domain wall can be moved by flowing the spin current. The spin-transfer effect was brought into the limelight by the progress in microfabrication techniques and the discovery of the giant magnetoresistance effect in magnetic multilayers. Berger, at the same time, separately studied the spin-transfer torque in a system similar to Slonczewski’s magnetic multilayered system and predicted spontaneous magnetization precession.

scholarly journals Double flow reversal in thin liquid films driven by megahertz-order surface vibration

2014 ◽  
Vol 470 (2169) ◽  
pp. 20130765 ◽  
Author(s):  
Amgad R. Rezk ◽  
Ofer Manor ◽  
Leslie Y. Yeo ◽  
James R. Friend
Keyword(s):  
Thin Films ◽  
Acoustic Waves ◽  
Surface Acoustic Waves ◽  
Intermolecular Forces ◽  
Liquid Films ◽  
Thin Liquid Films ◽  
Propagation Direction ◽  
Flow Reversal ◽  
Order Surface ◽  
Over Time

Arising from an interplay between capillary, acoustic and intermolecular forces, surface acoustic waves (SAWs) are observed to drive a unique and curious double flow reversal in the spreading of thin films. With a thickness at or less than the submicrometre viscous penetration depth, the film is seen to advance along the SAW propagation direction, and self-similarly over time t 1/4 in the inertial limit. At intermediate film thicknesses, beyond one-fourth the sound wavelength λ ℓ in the liquid, the spreading direction reverses, and the film propagates against the direction of the SAW propagation. The film reverses yet again, once its depth is further increased beyond one SAW wavelength. An unstable thickness region, between λ ℓ /8 and λ ℓ /4, exists from which regions of the film either rapidly grow in thickness to exceed λ ℓ /4 and move against the SAW propagation, consistent with the intermediate thickness films, whereas other regions decrease in thickness below λ ℓ /8 to conserve mass and move along the SAW propagation direction, consistent with the thin submicrometre films.

Accretion of Mass and Spin Angular Momentum by a Planet on an Eccentric Orbit

Icarus ◽  
1997 ◽  
Vol 127 (1) ◽  
pp. 65-92 ◽  
Author(s):  
Jack J. Lissauer ◽  
Alice F. Berman ◽  
Yuval Greenzweig ◽  
David M. Kary
Keyword(s):  
Angular Momentum ◽  
Spin Angular Momentum ◽  
Eccentric Orbit

LEAKY SURFACE ACOUSTIC WAVES IN SINGLE-CRYSTAL AlN SUBSTRATE

2004 ◽  
Vol 14 (03) ◽  
pp. 837-846 ◽  
Author(s):  
GANG BU ◽  
DAUMANTAS CIPLYS ◽  
MICHAEL S. SHUR ◽  
LEO J. SCHOWALTER ◽  
SANDRA B. SCHUJMAN ◽  
...  
Keyword(s):  
Single Crystal ◽  
Acoustic Waves ◽  
Electromechanical Coupling ◽  
Surface Acoustic Waves ◽  
Propagation Direction ◽  
Electromechanical Coupling Coefficient ◽  
Coupling Coefficients ◽  
Leaky Waves ◽  
Temperature Coefficient Of Frequency ◽  
Piezoelectric Constants

We report on the velocity V and the electromechanical coupling coefficient K2 of the first and the second leaky surface acoustic waves in various propagation directions in the a-plane AlN single-crystal. For c-propagation direction, the second leaky wave exhibited the velocity of 11016 m/s and K2 of 0.45%. For this direction, the temperature coefficient of frequency was found to be -30 ppm/°C. A near match of the velocities of the plane and leaky waves in the a-plane AlN allowed us to establish analytical relationships between the piezoelectric and elastic constants. A full set of elastic and piezoelectric constants of AlN has been evaluated by fitting the measured and calculated dependencies of velocities and electromechanical coupling coefficients on the propagation direction for both Rayleigh and leaky waves.

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