Asymmetric Berry-Phase Interference Patterns in a Single-Molecule Magnet

Quddusi, H. M.; Liu, Junjie; Singh, Simranjeet; Heroux, Katie J.; Barco, Enrique del; Hill, Stephen; Hendrickson, David N.

doi:10.1103/physrevlett.106.227201

Cited by 26 publications

(33 citation statements)

References 21 publications

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“…1C, were first observed in Fe 8 [11,12] and then in some other SMMs [13][14][15][16][17][18][19] by means of Landau-Zener magnetization relaxation experiments. Interference patterns measured on Fe 8 at very low temperatures, which correspond to tunneling via the ground state doublet m = ±10, are reproduced by the following spin Hamiltonian C/k B = −2.9 × 10 −5 K are magnetic anisotropy parameters, and g = 2.…”

Section: Pacs Numbersmentioning

confidence: 99%

Quantum Interference Oscillations of the Superparamagnetic Blocking in anFe8Molecular Nanomagnet

et al. 2013

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We show that the dynamic magnetic susceptibility and the superparamagnetic blocking temperature of an Fe8 single molecule magnet oscillate as a function of the magnetic field Hx applied along its hard magnetic axis. These oscillations are associated with quantum interferences, tuned by Hx, between different spin tunneling paths linking two excited magnetic states. The oscillation period is determined by the quantum mixing between the ground S = 10 and excited multiplets. These experiments enable us to quantify such mixing. We find that the weight of excited multiplets in the magnetic ground state of Fe8 amounts to approximately 11.6 %. PACS numbers:High-spin molecular clusters [1, 2] display superparamagnetic behavior, very much as magnetic nanoparticles typically do. Below a time-(or frequency-)dependent blocking temperature T b , the linear magnetic response "freezes" [3,4] and magnetization shows hysteresis [5]. The slow magnetic relaxation of these single-molecule magnets (SMMs) arises from anisotropy energy barriers separating spin-up and spin-down states. Because of their small size, the magnetic response shows also evidences for quantum phenomena, such as resonant spin tunneling [3,[6][7][8]. In the case of molecules that, like Fe 8 (cf Fig. 1A and [4]), have a biaxial magnetic anisotropy, tunneling between any pair of quasi-degenerate spin states ±m can proceed via two equivalent trajectories, which, as illustrated in Fig. 1B, cross the hard anisotropy plane close to the medium anisotropy axis. A magnetic field along the hard axis changes the phases of these tunneling paths, leading to either constructive or destructive interferences. This phenomenon is known as Berry phase interference [9,10].Experimental evidences for the ensuing oscillation of the quantum tunnel splitting ∆ m , shown in Fig. 1C, were first observed in Fe 8 [11,12] and then in some other SMMs [13][14][15][16][17][18][19] by means of Landau-Zener magnetization relaxation experiments. Interference patterns measured on Fe 8 at very low temperatures, which correspond to tunneling via the ground state doublet m = ±10, are reproduced by the following spin Hamiltonian C/k B = −2.9 × 10 −5 K are magnetic anisotropy parameters, and g = 2. The sizeable fourth-order parameter C reflects not only the intrinsic anisotropy but, mainly, it parameterizes quantum mixing of the S = 10 with excited multiplets (S-mixing) and how it influences quantum tunneling via the ground state [20].In the present paper, we study the influence of Berry phase interference on the ac magnetic susceptibility χ and T b of Fe 8 , that is, on those quantities that characterize the standard SMM (or superparamagnetic) behavior. Close to T b , magnetic relaxation is dominated by tunneling near the top of the anisotropy energy barrier, thus also near excited multiplets with S = 10. In this way, we

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Section: Pacs Numbersmentioning

confidence: 99%

Quantum Interference Oscillations of the Superparamagnetic Blocking in anFe8Molecular Nanomagnet

et al. 2013

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“…The observation of QTM in SMMs in the early 1990s [1][2][3] touched off a wave of explorations into the fundamental aspects of nanomagnetism and has since borne a wealth of fertile data and impacted on an extraordinarily broad range of science. One of the most prominent findings arose from the theoretical revelation of quantum phase interference as a modulator of QTM [4][5][6] and the subsequent experimental confirmation for several molecular symmetries [8][9][10][11][12], which established the importance of subtle contributions introduced by second (and higher) order molecular anisotropic interactions in shaping QTM behavior. It is in the kernel of this understanding where one finds profound insight into the relationship between the SOC symmetries and QTM, including the symmetryimposed spin selection rules that must be satisfied in order to break the energy degeneracy and allow tunneling to occur between a pair of molecular spin levels, labeled as m and m', at a QTM resonance k, defined as k = m'-m.…”

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confidence: 99%

Three-Leaf Quantum Interference Clovers in a Trigonal Single-Molecule Magnet

et al. 2014

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“…We will show that the geometric phase for the squeezed light in nano-systems described by the harmonic oscillator exhibits a novel distinct oscillation in time. Such oscillations of the geometric phase may significantly affect the pattern of interference phenomena [18] which are intrinsic in fundamental optical devices, such as interferometry [19], polarimeter [20], and microscopy [21]. We will also extend our theory to more complicated optical phenomena where the squeezed state undergoes one-photon processes [22].…”

Section: Introductionmentioning

confidence: 91%

Quadrature Squeezing and Geometric-Phase Oscillations in Nano-Optics

Choi

2020

Nanomaterials

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The geometric phase, as well as the familiar dynamical phase, occurs in the evolution of a squeezed state in nano-optics as an extra phase. The outcome of the geometric phase in that state is somewhat intricate: its time behavior exhibits a combination of a linear increase and periodic oscillations. We focus in this work on the periodic oscillations of the geometric phase, which are novel and interesting. We confirm that such oscillations are due purely to the effects of squeezing in the quantum states, whereas the oscillation disappears when we remove the squeezing. As the degree of squeezing increases in q-quadrature, the amplitude of the geometric-phase oscillation becomes large. This implies that we can adjust the strength of such an oscillation by tuning the squeezing parameters. We also investigate geometric-phase oscillations for the case of a more general optical phenomenon where the squeezed state undergoes one-photon processes. It is shown that the geometric phase in this case exhibits additional intricate oscillations with small amplitudes, besides the principal oscillation. Such a sub-oscillation exhibits a beating-like behavior in time. The effects of geometric-phase oscillations are crucial in a wide range of wave interferences which are accompanied by rich physical phenomena such as Aharonov–Bohm oscillations, conductance fluctuations, antilocalizations, and nondissipative current flows.

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Asymmetric Berry-Phase Interference Patterns in a Single-Molecule Magnet

Cited by 26 publications

References 21 publications

Quantum Interference Oscillations of the Superparamagnetic Blocking in anFe8Molecular Nanomagnet

Quantum Interference Oscillations of the Superparamagnetic Blocking in anFe8Molecular Nanomagnet

Three-Leaf Quantum Interference Clovers in a Trigonal Single-Molecule Magnet

Quadrature Squeezing and Geometric-Phase Oscillations in Nano-Optics

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