Enhancement of quantum tunneling for excited states in ferromagnetic particles

Liang, J.-Q.; Zhang, Y.-B.; Müller-Kirsten, Harald J W; Zhou, Jian‐Ge; Zimmerschied, F.; Pu, Fu‐Cho

doi:10.1103/physrevb.57.529

Cited by 38 publications

(38 citation statements)

References 26 publications

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“…[9] and which allows the explicit calculation of periodic instantons as well as the evaluation of their action, and we show that this model gives rise to a first order transition. The model is described in Refs.…”

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confidence: 78%

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Periodic Instantons and Quantum-Classical Transitions in Spin Systems

et al. 1998

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Some models allowing explicit calculation of periodic instantons and evaluation of their action are studied with regard to transitions from classical to quantum behaviour as the temperature is lowered and tunneling sets in. It is shown that (beyond a critical value of a coupling) the spin system considered acquires a first order transition as a result of the field dependence of its effective mass, whereas models with constant mass exhibit only second order transitions.Comment: 10 pages, 3 figure

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confidence: 78%

“…In Ref. [9] it is shown that the classical equation associated with the model possesses the following periodic instanton configuration f arcsin…”

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confidence: 99%

Periodic Instantons and Quantum-Classical Transitions in Spin Systems

et al. 1998

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“…reduces to the well known action [8,11,14,[17][18][19] when α = 0. The imaginary part leads to a phase in the Euclidean Feynman propagator which is 2s + 1 times the semiclassical phase θ s .…”

Section: Tunneling Splitting At the Ground Statementioning

confidence: 99%

Quantum phase interference for quantum tunneling in spin systems

et al. 2000

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The point-particle-like Hamiltonian of a biaxial spin particle with external magnetic field along the hard axis is obtained in terms of the potential field description of spin systems with exact spin-coordinate correspondence. The Zeeman energy term turns out to be an effective gauge potential which leads to a nonintegrable phase of the Euclidean Feynman propagator. The phase interference between clockwise and anticlockwise under barrier propagations is recognized explicitly as the Aharonov-Bohm effect. An additional phase which is significant for quantum phase interference is discovered with the quantum theory of spin systems besides the known phase obtained with the semiclassical treatment of spin. We also show the energy dependence of the * e-mail:jqliang@mail.sxu.edu.cn † e-mail: mueller1@pysik.uni-kl.de ‡ e-mail:dkpark@genphys.kyungnam.ac.kr 1 effect and obtain the tunneling splitting at excited states with the help of periodic instantons.

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“…The Feynman propagator equation (4) may be evaluated with the spin-coherent state path integrals. The spin-coherent state is defined byŜ · n|n = s|n where n = (sin θ cos ϕ, sin θ sin ϕ, cos θ) is a unit vector [24,25]. Regarding ϕ, p = s cos θ as canonical variables and integrating over variable p we obtain the effective Lagrangian given by…”

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confidence: 99%