Search results for "Zener diode"
showing 6 items of 6 documents
Landau-Zener problem in a three-level neutrino system with non-linear time dependence
2006
We consider the level-crossing problem in a three-level system with non-linearly time-varying Hamiltonian (time-dependence $t^{-3}$). We study the validity of the so-called independent crossing approximation in the Landau-Zener model by making comparison with results obtained numerically in density matrix approach. We also demonstrate the failure of the so-called "nearest zero" approximation of the Landau-Zener level-crossing probability integral.
Manipulation of the spin in single molecule magnets via Landau-Zener transitions
2011
We theoretically investigate the effects of a magnetic pulse on a single-molecule magnet (SMM) initially magnetized by a dc field along the easy axis of magnetization. In the Landau\char21{}Zener (LZ) scheme, it is shown that the final spin state is a function of the shape and duration of the pulse, conditioned by the decoherence time of the SMM. In the case of coherent tunneling, the asymmetric pulses are shown to reverse the direction of the magnetization, while the symmetric pulses can only decrease the value of the initial magnetization. It is also demonstrated that the application of an external variable dc field in the hard plane of magnetization provides the possibility to tune the r…
Coupling-assisted Landau-Majorana-Stückelberg-Zener transition in a system of two interacting spin qubits
2019
We analyse a system of two interacting spin-qubits subjected to a Landau-Majorana-Stuckelberg-Zener (LMSZ) ramp. We prove that LMSZ transitions of the two spin-qubits are possible without an external transverse static field since its role is played by the coupling between the spin-qubits. We show how such a physical effect could be exploited to estimate the strength of the interaction between the two spin-qubits and to generate entangled states of the system by appropriately setting the slope of the ramp. Moreover, the study of effects of the coupling parameters on the time-behaviour of the entanglement is reported. Finally, our symmetry-based approach allows us to discuss also effects stem…
Butterfly hysteresis curves generated by adiabatic Landau-Zener transitions
2006
Butterfly hysteresis curves observed in dynamical magnetization measurements on systems of low-spin magnetic molecules such as ${\mathrm{V}}_{15}$ can be explained by the interplay of adiabatic Landau-Zener transitions and relaxation. We investigate the magnetization dynamics analytically in the basis of the adiabatic energy levels of the spin $1∕2$, to a qualitative accordance with experimental observations. In particular, reversible behavior is found near zero field, the corresponding susceptibility being bounded by the equilibrium and adiabatic susceptibilities.
Dzyaloshinskii-Moriya and dipole-dipole interactions affect coupling-based Landau-Majorana-Stückelberg-Zener transitions
2020
It has been theoretically demonstrated that two spins (qubits or qutrits), coupled by exchange interaction only, undergo a coupling-based joint Landau-Majorana-St\"uckelberg-Zener (LMSZ) transition when a linear ramp acts upon one of the two spins. Such a transition, under appropriate conditions on the parameters, drives the two-spin system toward a maximally entangled state. In this paper, effects on the quantum dynamics of the two qudits, stemming from the Dzyaloshinskii-Moriya (DM) and dipole-dipole (d-d) interactions, are investigated qualitatively and quantitatively. The enriched Hamiltonian model of the two spins, shares with the previous microscopic one the same C2-symmetry which onc…
Landau-Majorana-Stuckelberg-Zener dynamics driven by coupling for two interacting qutrit systems
2019
A time-dependent model of two interacting spin qutrits is analyzed is analyzed and solved. The two interacting qutrits are subjected to a longitudinal field linearly varying over time as in the Landau-Majorana-St\"uckelberg- Zener (LMSZ) scenario. Although a transverse field is absent, we show the occurrence of LMSZ transitions assisted by the coupling between the two spin-qutrits. Such a physical effect permits us to estimate experimentally the coupling strength between the spins and allows the generation of entangled states of the two qutrits by appropriately setting the slope of the ramp. Furthermore, the possibility of local and nonlocal control as well as the existence of dark states o…