Subscribe to the gold package and get unlimited access to Shamra Academy
Register a new userControl of the Bose-Einstein Condensation of Magnons by the Spin-Hall Effect
62
0
0.0
(
0
)
Ask ChatGPT about the research
No Arabic abstract
Previously, it has been shown that rapid cooling of yttrium-iron-garnet/platinum (Pt) nano structures, preheated by an electric current sent through the Pt layer leads to overpopulation of a magnon gas and to subsequent formation of a Bose-Einstein condensate (BEC) of magnons. The spin Hall effect (SHE), which creates a spin-polarized current in the Pt layer, can inject or annihilate magnons depending on the electric current and applied field orientations. Here we demonstrate that the injection or annihilation of magnons via the SHE can prevent or promote the formation of a rapid cooling induced magnon BEC. Depending on the current polarity, a change in the BEC threshold of -8% and +6% was detected. These findings demonstrate a new method to control macroscopic quantum states, paving the way for their application in spintronic devices.
rate research
Read More
Gaseous Bose-Einstein condensates (BECs) have become an important test bed for studying the dynamics of quantized vortices. In this work we use two-photon Doppler sensitive Bragg scattering to study the rotation of sodium BECs. We analyze the microscopic flow field and present laboratory measurements of the coarse-grained velocity profile. Unlike time-of-flight imaging, Bragg scattering is sensitive to the direction of rotation and therefore to the phase of the condensate. In addition, we have non-destructively probed the vortex flow field using a sequence of two Bragg pulses.
In a recent paper cite{Radu}, Radu textit{et al.} report experimental results they claim to support Bose-Einstein condensation (BEC) of magnons in Cs$_2$CuCl$_4$. It is true that an experimentally measured critical power law scaling exponent in agreement with the BEC universality class would support the realization of a BEC in magnetic systems that order as a canted antiferromagnet. It can be shown, however, that the claim of Radu {it et al.} is overstated in this instance, because their determination of the critical exponent $phi$ relies on a model-dependent theoretical approximation to the critical field $H_{textrm{c1}}$ for which the associated errors are neglected. We show that when these errors are included, the uncertainty in the obtained exponent is so large that the available experimental data cannot be used to differentiate between contending universality classes.
Bose-Einstein condensation in a gas of magnons pumped by an incoherent pumping source is experimentally studied at room temperature. We demonstrate that the condensation can be achieved in a gas of bosons under conditions of incoherent pumping. Moreover, we show the critical transition point is almost independent of the frequency spectrum of the pumping source and is solely determined by the density of magnons. The electromagnetic power radiated by the magnon condensate was found to scale quadratically with the pumping power, which is in accordance with the theory of Bose-Einstein condensation in magnon gases.
The Bose-Einstein condensation of $alpha$ partciles in the multicomponent environment of dilute, warm nuclear matter is studied. We consider the cases of matter composed of light clusters with mass numbers $Aleq 4$ and matter that in addition these clusters contains $isotope[56]{Fe}$ nuclei. We apply the quasiparticle gas model which treats clusters as bound states with infinite life-time and binding energies independent of temperature and density. We show that the $alpha$ particles can form a condensate at low temperature $Tle 2$ MeV in such matter in the first case. When the $isotope[56]{Fe}$ nucleus is added to the composition the cluster abundances are strongly modified at low temperatures, with an important implication that the $alpha$ condensation at these temperatures is suppressed.
Control of magnetization dynamics is one of the primary goals in spintronics. It has been demonstrated using spin Hall effect i.e charge current to spin current conversion in non-magnetic metal which has large spin-orbit coupling such as Pt, W etc. Recently different groups have shown generation of spin current in Pt, W while thermal gradient is created by virtue of spin Nernst effect. In this work we show the evidence of magnetization control by spin Nernst torque in Pt/Py bi-layer. We compared relative strength of spin Nernst Torque and spin Hall torque by measuring the systematic variation of magnetic linewidth on application of constant heat or charge current. Spin-torque ferromagnetic resonance (ST-FMR) technique is adopted to excite the magnet and to measure line-width precisely from the symmetric and anti-symmetric voltage component. Control of magnetization dynamics by spin Nernst torque will emerge as an alternative way to manipulate nano-magnets.
Log in to be able to interact and post comments
comments
Fetching comments
Sign in to be able to follow your search criteria
