scholarly journals Exceptional points in classical spin dynamics

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Alexey Galda ◽  
Valerii M. Vinokur
Keyword(s):  
High Efficiency ◽  
Spin Dynamics ◽  
Special Kind ◽  
Dissipative Systems ◽  
Exceptional Point ◽  
Single Spin ◽  
Resonant Modes ◽  
Uniform Magnetization ◽  
Physical Consequences ◽  
Spin Devices

AbstractNon-conservative physical systems admit a special kind of spectral degeneracy, known as exceptional point (EP), at which eigenvalues and eigenvectors of the corresponding non-Hermitian Hamiltonian coalesce. Dynamical parametric encircling of the EP can lead to non-adiabatic evolution associated with a state flip, a sharp transition between the resonant modes. Physical consequences of the dynamical encircling of EPs in open dissipative systems have been explored in optics and photonics. Building on the recent progress in understanding the parity-time ($${\mathscr{P}}{\mathscr{T}}$$PT)-symmetric dynamics in spin systems, we use topological properties of EPs to implement chiral non-reciprocal transmission of a spin through the material with non-uniform magnetization, like helical magnet. We consider an exemplary system, spin-torque-driven single spin described by the time-dependent non-Hermitian Hamiltonian. We show that encircling individual EPs in a parameter space results in non-reciprocal spin dynamics and find the range of optimal protocol parameters for high-efficiency asymmetric spin filter based on this effect. Our findings offer a platform for non-reciprocal spin devices for spintronics and magnonics.

scholarly journals Multicolor Emission from Ultraviolet GaN-based Photonic Quasicrystal Nanopyramid Structure with Semipolar InxGa1-xN/GaN Multiple Quantum Wells

2021 ◽  
Author(s):  
Cheng-Chang Chen ◽  
Hsiang-Ting Lin ◽  
Shih-Pang Chang ◽  
Hao-Chung Kuo ◽  
Hsiao-Wen Hung ◽  
...  
Keyword(s):  
Quantum Wells ◽  
Nanoimprint Lithography ◽  
Optical Pumping ◽  
High Efficiency ◽  
Multiple Quantum Wells ◽  
Multiple Quantum ◽  
Large Area ◽  
Resonant Modes ◽  
Color Emission ◽  
Photonic Quasicrystal

Abstract In this study, we demonstrated large-area high quality multi-color emission from the 12-fold symmetric GaN photonic quasicrystal nanorod device which was fabricated using the nanoimprint lithography technology and multiple quantum wells regrowth procedure. High-efficiency blue and green color emission wavelengths of 460 and 520 nm from the regrown InxGa1−xN/GaN multiple quantum wells were observed under optical pumping conditions. To confirm the strongly coupling between the quantum well emissions and the photonic crystal band-edge resonant modes, the finite-element method (FEM) was applied to perform a simulation of the 12-fold symmetry photonic quasicrystal lattices.

scholarly journals ITERATED TABU SEARCH: AN IMPROVEMENT TO STANDARD TABU SEARCH

2006 ◽  
Vol 35 (3) ◽  
Author(s):  
Alfonsas Misevicius ◽  
Antanas Lenkevicius ◽  
Dalius Rubliauskas
Keyword(s):  
Combinatorial Optimization ◽  
Tabu Search ◽  
High Efficiency ◽  
Optimization Problems ◽  
Quadratic Assignment Problem ◽  
Special Kind ◽  
Quadratic Assignment ◽  
Combinatorial Optimization Problems ◽  
Diversification Mechanism ◽  
Iterated Tabu Search

The goal of this paper is to discuss the tabu search (TS) meta-heuristic and its enhancement for combinatorial optimization problems. Firstly, the issues related to the principles and specific features of the standard TS are concerned. Further, a promising extension to the classical tabu search scheme is introduced. The most important component of this extension is a special kind of diversification mechanism. We give the paradigm of this new improved TS strategy, which is called an iterated tabu search (ITS). ITS was applied to the difficult combinatorial optimization problems, the traveling salesman problem (TSP) and the quadratic assignment problem (QAP). The results of the experiments with the TSP and QAP show the high efficiency of the ITS strategy. The outstanding performance of ITS is also demonstrated by the fact that the new record-breaking solutions were found for the hard QAP instances - tai80a and tai100a.

scholarly journals High-efficiency resonant amplification of weak magnetic fields for single spin magnetometry at room temperature

2015 ◽  
Vol 10 (6) ◽  
pp. 541-546 ◽  
Author(s):  
Luka Trifunovic ◽  
Fabio L. Pedrocchi ◽  
Silas Hoffman ◽  
Patrick Maletinsky ◽  
Amir Yacoby ◽  
...  
Keyword(s):  
Magnetic Fields ◽  
Room Temperature ◽  
High Efficiency ◽  
Single Spin ◽  
Weak Magnetic Fields

scholarly journals Coherent single-spin electron resonance spectroscopy manifested at an exceptional-point singularity in doped polyacetylene

2021 ◽  
Vol 103 (4) ◽  
Author(s):  
Yujin Dunham ◽  
Kazuki Kanki ◽  
Savannah Garmon ◽  
Satoshi Tanaka ◽  
Gonzalo Ordonez
Keyword(s):  
Exceptional Point ◽  
Resonance Spectroscopy ◽  
Point Singularity ◽  
Electron Resonance ◽  
Single Spin

scholarly journals Enhanced energy harvesting near exceptional points in systems with (pseudo-)PT-symmetry

2021 ◽  
Vol 4 (1) ◽  
Author(s):  
Lucas J. Fernández-Alcázar ◽  
Rodion Kononchuk ◽  
Tsampikos Kottos
Keyword(s):  
Energy Harvesting ◽  
Thermal Radiation ◽  
Research Agenda ◽  
High Efficiency ◽  
Pt Symmetry ◽  
Exceptional Point ◽  
Exceptional Points ◽  
Maximum Work ◽  
Self Powered ◽  
Vibrational Noise

AbstractExceptional point degeneracies, occurring in non-Hermitian systems, have challenged many well established concepts and led to the development of remarkable technologies. Here, we propose a family of autonomous motors whose operational principle relies on exceptional points via the opportune implementation of a (pseudo-)PT-symmetry and its spontaneous or explicit violation. These motors demonstrate a parameter domain of coexisting high efficiency and maximum work. In the photonic framework, they can be propelled by thermal radiation from the ambient thermal reservoirs and utilized as autonomous self-powered microrobots, or as micro-pumps for microfluidics in biological environments. The same designs can be also implemented with electromechanical elements for harvesting ambient mechanical (e.g., vibrational) noise for powering a variety of auxiliary systems. We expect that our proposal will contribute to the research agenda of energy harvesting by introducing concepts from mathematical and non-Hermitian wave physics.

scholarly journals HADRON SPIN DYNAMICS

2003 ◽  
Vol 18 (08) ◽  
pp. 1531-1550 ◽  
Author(s):  
STANLEY J. BRODSKY
Keyword(s):  
Spin Asymmetry ◽  
Spin Dynamics ◽  
Probability Distributions ◽  
Magnetic Moments ◽  
Hadron Structure ◽  
Spin Asymmetries ◽  
Single Spin ◽  
Spin Effects ◽  
Single Spin Asymmetries ◽  
Fock State

Spin effects in exclusive and inclusive reactions provide an essential new dimension for testing QCD and unraveling hadron structure. Remarkable new experiments from SLAC, HERMES (DESY), and Jefferson Lab present many challenges to theory, including measurements at HERMES and SMC of the single spin asymmetries in ep → e′ π X where the proton is polarized normal to the scattering plane. This type of single spin asymmetry may be due to the effects of rescattering of the outgoing quark on the spectators of the target proton, an effect usually neglected in conventional QCD analyses. Many aspects of spin, such as single-spin asymmetries and baryon magnetic moments are sensitive to the dynamics of hadrons at the amplitude level, rather than probability distributions. I will illustrate the novel features of spin dynamics for relativistic systems by examining the explicit form of the light-front wavefunctions for the two-particle Fock state of the electron in QED, thus connecting the Schwinger anomalous magnetic moment to the spin and orbital momentum carried by its Fock state constituents and providing a transparent basis for understanding the structure of relativistic composite systems and their matrix elements in hadronic physics. I also present a survey of outstanding spin puzzles in QCD, particularly ANN in elastic pp scattering, the J/ψ → ρπ puzzle, and J/ψ polarization at the Tevatron.

scholarly journals Simulating single-spin dynamics on an IBM five-qubit chip

2020 ◽  
Vol 42 ◽  
Author(s):  
Émerson M. Alves ◽  
Francisco D.S. Gomes ◽  
Hércules S. Santana ◽  
Alan C. Santos
Keyword(s):  
Spin Dynamics ◽  
Single Spin

scholarly journals Multicolor Emission from Ultraviolet GaN-Based Photonic Quasicrystal Nanopyramid Structure with Semipolar InxGa1−xN/GaN Multiple Quantum Wells

2021 ◽  
Vol 16 (1) ◽  
Author(s):  
Cheng-Chang Chen ◽  
Hsiang-Ting Lin ◽  
Shih-Pang Chang ◽  
Hao-Chung Kuo ◽  
Hsiao-Wen Hung ◽  
...  
Keyword(s):  
Quantum Wells ◽  
Nanoimprint Lithography ◽  
Optical Pumping ◽  
High Efficiency ◽  
Multiple Quantum Wells ◽  
Multiple Quantum ◽  
Large Area ◽  
Resonant Modes ◽  
Color Emission ◽  
Photonic Quasicrystal

AbstractIn this study, we demonstrated large-area high-quality multi-color emission from the 12-fold symmetric GaN photonic quasicrystal nanorod device which was fabricated using the nanoimprint lithography technology and multiple quantum wells regrowth procedure. High-efficiency blue and green color emission wavelengths of 460 and 520 nm from the regrown InxGa1−xN/GaN multiple quantum wells were observed under optical pumping conditions. To confirm the strong coupling between the quantum well emissions and the photonic crystal band-edge resonant modes, the finite-element method was applied to perform a simulation of the 12-fold symmetry photonic quasicrystal lattices.

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