All-spin-based ultrafast nanologic elements with a ${\mathrm{Ni}}_{4}$ cluster

All-spin-based ultrafast nanologic elements with a ${Ni}_{4}$ cluster

D. Chaudhuri, G. Lefkidis, and W. Hübner

Phys. Rev. B 96, 184413 – Published 10 November 2017

Abstract

Starting from high-level ab initio calculations, we present ultrafast spin dynamical effects and all-spin-based nanologic elements on a ${Ni}_{4}$ cluster. The predominant underlying mechanisms for our operations are optically induced coherent $Λ$ processes, the optimized parameters of which are obtained from a dedicated genetic algorithm search. The geometry of the cluster exhibits a high degree of spin localization. Thus, maneuvering the spin localizations we construct a pure-spin OR gate. Additionally, functional intramolecular cooperative effects such as spin bifurcation and spin merging are introduced that facilitate the setup of the latter. In the which-path information effect the phase of the final spin state is exploited to reveal the path traveled by the spin in a two-step spin transfer scenario. This is beneficial for both classical and quantum computations on small spatial and temporal scales.

Received 13 July 2016
Revised 25 October 2017

DOI:https://doi.org/10.1103/PhysRevB.96.184413

Physics Subject Headings (PhySH)

Molecular magnetism Spintronics

Molecular magnets

Coupled cluster

Condensed Matter, Materials & Applied Physics

Authors & Affiliations

D. Chaudhuri, G. Lefkidis^*, and W. Hübner

Department of Physics and Research Center OPTIMAS, University of Kaiserslautern, P.O. Box 3049, 67653 Kaiserslautern, Germany

^*lefkidis@physik.uni-kl.de

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Vol. 96, Iss. 18 — 1 November 2017

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Figure 1
Optimized structure of ${Ni}_{4}$ at the Hartree-Fock level, for which a planar geometry is imposed (see text).
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Figure 2
Levels of the optimized ${Ni}_{4}$ as calculated with the SAC-CI method for states up to 4 eV. Left: without spin-orbit coupling, triplet states are given with the solid black lines, singlet states with the red dashed lines, and quintet states with dotted-dashed green lines. Right: after the inclusion of spin orbit coupling and restricting only to the singlet and the triplet channel (there can be no distinction between singlets and triplets after spin-orbit coupling).
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Figure 3
Level scheme of the model Hamiltonian as a function of an external magnetic field. There is one quintet (solid black lines), three triplets (dashed red lines), and two singlets (dashed green lines). (a) Only isotropic bilinear and biquadratic exchange interaction terms, (b) isotropic bilinear and biquadratic exchange plus Dzyaloshinksii-Moriya interaction terms, (c) anisotropic bilinear, biquadratic, and Dzyaloshinskii-Moriya terms. The symmetry reduction (and hence the level splitting) of the anisotropic bilinear and the Dzyaloshinksii-Moriya term are similar in nature but significantly differ in magnitude.
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Figure 4
Schematic showing a series of spin transfer scenarios between the magnetic centers along with the transition time for the processes. The red and the green arrows indicate the initial and the final states, respectively. The arrows do not refer to classical spins; they merely visualize the spin-density localization of the quantum mechanical spin operators $〈 {\hat{S}}_{x} 〉$ , $〈 {\hat{S}}_{y} 〉$ , and $〈 {\hat{S}}_{z} 〉$ .
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Figure 5
Spin bifurcation scenario in ${Ni}_{4}$ . (a) Population transfer from the initial state $| 25 〉$ (solid black) to the final state $| 23 〉$ (dashed red). (b) The time-resolved spin expectation values. (c) Envelope of the optimized laser pulse. (d) Schematic of the spin-bifurcation scenario. The arrows do not refer to classical spins; they merely visualize the spin density localization of the quantum mechanical spin operators $〈 {\hat{S}}_{x} 〉$ , $〈 {\hat{S}}_{y} 〉$ , and $〈 {\hat{S}}_{z} 〉$ .
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Figure 6
Schematic of the molecular OR gate. Logic values A and B are the inputs at Ni2 and Ni3 and Q=A $\cup$ B is the logical output at Ni4. The arrows do not refer to classical spins; they merely visualize the spin density localization of the quantum mechanical spin operators $〈 {\hat{S}}_{x} 〉$ , $〈 {\hat{S}}_{y} 〉$ , and $〈 {\hat{S}}_{z} 〉$ .
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Physical Review B

covering condensed matter and materials physics

All-spin-based ultrafast nanologic elements with a ${Ni}_{4}$ cluster

D. Chaudhuri, G. Lefkidis, and W. Hübner

Phys. Rev. B 96, 184413 – Published 10 November 2017

Abstract

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Physical Review B

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All-spin-based ultrafast nanologic elements with a Ni4 cluster

D. Chaudhuri, G. Lefkidis, and W. Hübner

Phys. Rev. B 96, 184413 – Published 10 November 2017

Abstract

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All-spin-based ultrafast nanologic elements with a ${Ni}_{4}$ cluster