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Spin-½

About: Spin-½ is a research topic. Over the lifetime, 40423 publications have been published within this topic receiving 796639 citations.


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Journal ArticleDOI
TL;DR: Two-dimensional magic-angle spinning (triple quantum, single quantum) correlation pulse sequences and phase cycles based on the technique of Frydman and Harwood for the reconstruction of the isotropic spectrum of half-integer spin quadrupolar nuclei broadened to second-order are described.

381 citations

Journal ArticleDOI
TL;DR: In this paper, a new class of hybrid quantum systems based on collective spin excitations in ferromagnetic materials has led to a diverse set of experimental platforms which are outlined in this review article.
Abstract: Engineered quantum systems enabling novel capabilities for communication, computation, and sensing have blossomed in the last decade. Architectures benefiting from combining distinct and complementary physical quantum systems have emerged as promising platforms for developing quantum technologies. A new class of hybrid quantum systems based on collective spin excitations in ferromagnetic materials has led to the diverse set of experimental platforms which are outlined in this review article. The coherent interaction between microwave cavity modes and collective spin-wave modes is presented as the backbone of the development of more complex hybrid quantum systems. Indeed, quanta of excitation of the spin-wave modes, called magnons, can also interact coherently with optical photons, phonons, and superconducting qubits in the fields of cavity optomagnonics, cavity magnomechanics, and quantum magnonics, respectively. Notably, quantum magnonics provides a promising platform for performing quantum optics experiments in magnetically-ordered solid-state systems. Applications of hybrid quantum systems based on magnonics for quantum information processing and quantum sensing are also outlined briefly.

379 citations

Journal ArticleDOI
TL;DR: In this article, the authors give a general introduction to quantum phase transitions in strongly correlated electron systems, which occur at zero temperature when a non-thermal parameter g such as the pressure, chemical concentration or magnetic field is tuned to a critical value.
Abstract: We give a general introduction to quantum phase transitions in strongly correlated electron systems. These transitions, which occur at zero temperature when a non-thermal parameter g such as the pressure, chemical concentration or magnetic field is tuned to a critical value, are characterized by a dynamie exponent z related to the energy and length scales δ and ∂. We show how one can derive an effective bosonic model associated with fluctuations in the ordering fields. Simple arguments based on an expansion to first order in the effective interaction u allow us to define an upper critical dimension D c = 4 (where D = d + z and d is the spatial dimension) below which the mean-field description is no longer valid. We present an alternative tricritical crossover approach valid at D < D c in the large-N limit. We emphasize the role of perturbative renormalization group approaches and self-consistent renormalized spin fluctuation theories in understanding the quantum-classical crossover in the vicinit...

379 citations

Journal ArticleDOI
22 Aug 2002-Nature
TL;DR: How unusual composite spin degrees of freedom can emerge from frustrated magnetic interactions in the cubic spinel ZnCr2O4, the long-sought local zero energy modes for the pyrochlore lattice is reported.
Abstract: Frustrated systems are ubiquitous1,2,3, and they are interesting because their behaviour is difficult to predict; frustration can lead to macroscopic degeneracies and qualitatively new states of matter. Magnetic systems offer good examples in the form of spin lattices, where all interactions between spins cannot be simultaneously satisfied4. Here we report how unusual composite spin degrees of freedom can emerge from frustrated magnetic interactions in the cubic spinel ZnCr2O4. Upon cooling, groups of six spins self-organize into weakly interacting antiferromagnetic loops, whose directors—the unique direction along which the spins are aligned, parallel or antiparallel—govern all low-temperature dynamics. The experimental evidence comes from a measurement of the magnetic form factor by inelastic neutron scattering; the data show that neutrons scatter from hexagonal spin clusters rather than individual spins. The hexagon directors are, to a first approximation, decoupled from each other, and hence their reorientations embody the long-sought local zero energy modes for the pyrochlore lattice.

378 citations

Journal ArticleDOI
TL;DR: In this article, a generalized stochastic Landau-Lifshitz equation and its corresponding Fokker-Planck equation were proposed for the magnetization dynamics in the presence of spin-transfer torques.
Abstract: We propose a generalized stochastic Landau-Lifshitz equation and its corresponding Fokker-Planck equation for the magnetization dynamics in the presence of spin-transfer torques. Since the spin-transfer torque can pump a magnetic energy into the magnetic system, the equilibrium temperature of the magnetic system is ill defined. We introduce an effective temperature based on a stationary solution of the Fokker-Planck equation. In the limit of high-energy barriers, the law of thermal agitation is derived. We find that the N\'eel-Brown relaxation formula remains valid as long as we replace the temperature by an effective one that is linearly dependent on the spin torque. We carry out the numerical integration of the stochastic Landau-Lifshitz equation to support our theory. Our results agree with existing experimental data.

378 citations


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Performance
Metrics
No. of papers in the topic in previous years
YearPapers
202234
20212,352
20201,787
20191,748
20181,696
20171,621