92 research outputs found
Nonlinear enhancement of coherent magnetization dynamics
Magnets are interesting materials for classical and quantum information
technologies. However, the short decoherence and dephasing times that determine
the scale and speed of information networks, severely limit the appeal of
employing the ferromagnetic resonance. Here we show that the lifetime and
coherence of the uniform Kittel mode can be enhanced by 3-magnon
interaction-induced mixing with the long-lived magnons at the minima of the
dispersion relation. Analytical and numerical calculations based on this model
explain recent experimental results and predict experimental signatures of
quantum coherence
Swapping Labeled Tokens on Graphs
Consider a puzzle consisting of n tokens on an n-vertex graph, where each token has a distinct starting vertex and a distinct target vertex it wants to reach, and the only allowed transformation is to swap the tokens on adjacent vertices. We prove that every such puzzle is solvable in O(n [superscript 2]) token swaps, and thus focus on the problem of minimizing the number of token swaps to reach the target token placement. We give a polynomial-time 2-approximation algorithm for trees, and using this, obtain a polynomial-time 2α-approximation algorithm for graphs whose tree α-spanners can be computed in polynomial time. Finally, we show that the problem can be solved exactly in polynomial time on complete bipartite graphs.Japan. Ministry of Education, Culture, Sports, Science and Technology (Japan Society for the Promotion of Science ELC Project Grant 24.3660)Japan. Ministry of Education, Culture, Sports, Science and Technology (Japan Society for the Promotion of Science ELC Project Grant 24106010)Japan. Ministry of Education, Culture, Sports, Science and Technology (Japan Society for the Promotion of Science ELC Project Grant 24700130)Japan. Ministry of Education, Culture, Sports, Science and Technology (Japan Society for the Promotion of Science ELC Project Grant 25106502)Japan. Ministry of Education, Culture, Sports, Science and Technology (Japan Society for the Promotion of Science ELC Project Grant 25106504)Japan. Ministry of Education, Culture, Sports, Science and Technology (Japan Society for the Promotion of Science ELC Project Grant 25330003
Nonlinear magnon polaritons
We experimentally and theoretically demonstrate that nonlinear spin-wave
interactions suppress the hybrid magnon-photon quasiparticle or "magnon
polariton" in microwave spectra of an yttrium iron garnet film detected by an
on-chip split-ring resonator. We observe a strong coupling between the Kittel
and microwave cavity modes in terms of an avoided crossing as a function of
magnetic fields at low microwave input powers, but a complete closing of the
gap at high powers. The experimental results are well explained by a
theoretical model including the three-magnon decay of the Kittel magnon into
spin waves. The gap closure originates from the saturation of the ferromagnetic
resonance above the Suhl instability threshold by a coherent back reaction from
the spin waves.Comment: 6 page
Spin colossal magnetoresistance in an antiferromagnetic insulator
Colossal magnetoresistance (CMR) refers to a large change in electrical conductivity induced by a magnetic field in the vicinity of a metal–insulator transition and has inspired extensive studies for decades1,2. Here we demonstrate an analogous spin effect near the Néel temperature, TN = 296 K, of the antiferromagnetic insulator Cr2O3. Using a yttrium iron garnet YIG/Cr2O3/Pt trilayer, we injected a spin current from the YIG into the Cr2O3 layer and collected, via the inverse spin Hall effect, the spin signal transmitted into the heavy metal Pt. We observed a two orders of magnitude difference in the transmitted spin current within 14 K of the Néel temperature. This transition between spin conducting and non-conducting states was also modulated by a magnetic field in isothermal conditions. This effect, which we term spin colossal magnetoresistance (SCMR), has the potential to simplify the design of fundamental spintronics components, for instance, by enabling the realization of spin-current switches or spin-current-based memories
Regulation of melanin-concentrating hormone receptor 1 signaling by RGS8 with the receptor third intracellular loop
Melanin-concentrating hormone (MCH) receptor 1 (MCH1R) belongs to the class A G protein-coupled receptors (GPCRs). The MCH-MCH1R system plays a central role in energy metabolism, and thus the regulation of signaling pathways activated by this receptor is of particular interest. Regulator of G protein signaling (RGS) proteins work by increasing the GTPase activity of G protein α subunits and attenuate cellular responses coupled with G proteins. Recent evidence has shown that RGS proteins are not simple G protein regulators but equally inhibit the signaling from various GPCRs. Here, we demonstrate that RGS8, which is highly expressed in the brain, functions as a negative modulator of MCH1R signaling. By using biochemical approaches, RGS8 was found to selectively and directly bind to the third intracellular (i3) loop of MCH1R in vitro. When expressed in HEK293T cells, RGS8 and MCH1R colocalized to the plasma membrane and RGS8 potently inhibited the calcium mobilization induced by MCH. The N-terminal 9 amino acids of RGS8 were required for the optimal capacity to downregulate the receptor signaling. Furthermore, Arg253 and Arg256 at the distal end of the i3 loop were found to comprise a structurally important site for the functional interaction with RGS8, since coexpression of RGS8 with R253Q/R256Q mutant receptors resulted a loss of induction of MCH-stimulated calcium mobilization. This functional association suggests that RGS8 may represent a new therapeutic target for the development of novel pharmaceutical agents
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