Related papers: Spin wave amplification through superradiance
It is shown that a sub-luminal electromagnetic plasma wave, propagating in phase with a background sub-luminal gravitational wave in a dispersive medium, can undergo parametric amplification. For this phenomena to occur, the dispersive…
In the usual picture of Hawking radiation, the emission is spontaneous; it is caused by nothing. In contrast, the radiation from the ringdown after a black-hole merger is caused dynamically by the fluctuations of the event horizon. We…
The gravitational waves and energy radiations from a spinning compact object with stellar mass in a circular orbit in the equatorial plane of a supermassive Kerr black hole are investigated in this paper. The effect how the spin acts on…
Using the complete classification of the bases in the rotating black hole background we separate superradiance from the Hawking effect. We first find that there is spontaneous particle creation for fermions by the potential outside the…
The condition for the existence of the superradiance modes is derived for the incident scalar, electromagnetic and gravitational waves when the spacetime background is a higher-dimensional rotating black hole with multiple angular momentum…
We introduce multiplexed atom-cavity quantum electrodynamics with an atomic ensemble coupled to a single optical cavity mode. Multiple Raman dressing beams establish cavity-coupled spin-wave excitations with distinctive spatial profiles.…
We demonstrate spin pumping driven by a strongly coupled magnon-photon system using a ferromagnet-coplanar superconducting resonator hybrid system at 1.4 K. Electrical readout via the inverse spin-Hall effect reveals characteristic coupling…
Using the analogy between a shrinking fluid vortex (`draining bathtub'), modelled as a (2+1) dimensional fluid flow with a sink at the origin, and a rotating (2+1) dimensional black hole with an ergosphere, it is shown that a scalar sound…
The authors have investigated the contribution of the surface spin waves to spin pumping. A Pt/NiFe bilayer has been used for measuring spin waves and spin pumping signals simultaneously. The theoretical framework of spin pumping resulting…
Properties are discussed of a ferromagnetic junction of the type "rod contacting with film". Very high current density of the order of $10^9$ A/cm$^2$ may be achieved in the contact region. We show it can lead to inversion of population of…
Composite optical systems can show compelling collective dynamics. For instance, the cooperative decay of quantum emitters into a common radiation mode can lead to superradiance, where the emission rate of the ensemble is larger than the…
An atom in open space can be detected by means of resonant absorption and reemission of electromagnetic waves, known as resonance fluorescence, which is a fundamental phenomenon of quantum optics. We report on the observation of scattering…
Fast radio bursts (FRBs) are extremely energetic radio transients, some are generated in magnetar magnetospheres and winds. Despite a growing number of observations, their emission mechanisms remain elusive. It has recently been proposed…
It is shown that the superradiance modes always exist in the radiation by the $(4+n)$-dimensional rotating black holes. Using a Bekenstein argument the condition for the superradiance modes is shown to be $0 < \omega < m \Omega$ for the…
Circuit theory has been tremendously successful in translating physical equations into circuit elements in organized form for further analysis and proposing creative designs for applications. With the advent of new materials and phenomena…
We demonstrate using micromagnetic simulations and a theoretical model that a gradient in the saturation magnetization ($M_s$) of a perpendicularly magnetized ferromagnetic film induces a non-reciprocal spin wave propagation and,…
The spin Hall effect in a heavy metal intercorrelates an AC electric current to the magnetization dynamics in an adjacent ferromagnet, which manifests as an electric reactance in the system's current-voltage response. We present a…
Spin dynamics of assemblies of magnetic nanomolecules and nanoclusters can be made coherent by inserting the sample into a coil of a resonant electric circuit. Coherence is organized through the arising feedback magnetic field of the coil.…
Periodic excitation of electron spin polarization by consecutive laser pulses in phase with Larmor spin precession about a magnetic field results in resonant spin amplification (RSA). We observe a drastic modification of RSA in $n$-doped…
Time-reflection occurs when a wave is propagating in a medium undergoing a large and abrupt change in its properties: the original wave splits into a time-refracted wave and a time-reflected wave, each displaying different features. The…