Magnetic Dipolar Ordering and Quantum Phase Transition in an<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:msub><mml:mi>Fe</mml:mi><mml:mn>8</mml:mn></mml:msub></mml:math>Molecular Magnet

Burzurí, Enrique; Luìs, Fernando; Barbara, B.; Ballou, R.; Ressouche, E.; Montero, Oscar; Campo, Javier; Maegawa, Satoru

doi:10.1103/physrevlett.107.097203

Cited by 43 publications

(48 citation statements)

References 43 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…By bottom-up chemical synthesis, arrays of these MMs, with aligned magnetic axes, are packed into a single crystal. Due to the relatively large intermolecular spacing, the exchange interactions between the molecules are negligible 19 . The giant-spin S = 10 multiplet of a single MM is described by the following Hamiltonian:…”

mentioning

confidence: 99%

“…The molecular size and net spin of a MM lie in between those of magnetic nanoparticles and of paramagnetic ions. At low temperatures, these molecular clusters show magnetic hysteresis, thus magnetic memory 15,16 , and display genuinely quantum phenomena, such as spin tunnelling 17 , quantum spin interference 16,18 and quantum phase transitions 19 . Each Fe 8 molecule, sketched in Fig.…”

mentioning

confidence: 99%

“…Furthermore, this temperature is well above the dipolar ferromagnetic ordering temperature T c = 0.6 K of Fe 8 (ref. 19 ), so that the molecular spins orient randomly along the anisotropy axis when no H z bias is applied. To erase a classical bit register, the effective barriers separating the two binary states of each bit are lowered and thermal fluctuations allow the system to fluctuate between these quasi-degenerate states.…”

mentioning

confidence: 99%

See 2 more Smart Citations

Quantum Landauer erasure with a molecular nanomagnet

et al. 2018

Self Cite

View full text Add to dashboard Cite

The erasure of a bit of information is an irreversible operation whose minimal entropy production of k B ln 2 is set by the Landauer limit 1 . This limit has been verified in a variety of classical systems, including particles in traps 2,3 and nanomagnets 4 . Here, we extend it to the quantum realm by using a crystal of molecular nanomagnets as a quantum spin memory and showing that its erasure is still governed by the Landauer principle. In contrast to classical systems, maximal energy efficiency is achieved while preserving fast operation owing to its high-speed spin dynamics. The performance of our spin register in terms of energy-time cost is orders of magnitude better than existing memory devices to date. The result shows that thermodynamics sets a limit on the energy cost of certain quantum operations and illustrates a way to enhance classical computations by using a quantum system.While a computation performed with an ideal binary logic gate (for example, NOT) has no lower energy dissipation limit [5][6][7] , one carried out in a memory device does. The reason is that in the former the bit is merely displaced isentropically in the space of states, whereas in the latter the minimal operation, called Landauer erasure, entails resetting the memory irrespective of its initial state. Let us see how this erasure applies to a classical N-bit register (Fig. 1a, left) and how the Landauer limit comes about. In the first stage, each bit of the register, in a definite state '0' or '1' , is allowed to explore the two binary states by lowering the potential barrier and through the action of temperature fluctuations. This doubling of the phase space is accompanied by an entropy production Δ S = k B ln 2 per bit, where k B is the Boltzmann constant. In the second stage, a work W ≥ TΔ S is required to reduce the register's entropy and phase space to their initial values 8 . The limit W = TΔ S is reached only if this reduction is carried out reversibly. This can be achieved when using a frictionless system in a quasi-static fashion (that is, at timescales slower than its relaxation time τ rel ), so that unwanted memory and hysteresis effects are avoided. For this reason, slow (fast) operation-with respect to the system-dependent τ rel -is generally associated with a lower (higher) dissipation.This complementarity between work and time suggests considering the product Wτ rel -rather than either of the two-as the figure of merit assessing the energy-time cost of a computation. On one hand, driven by the demand for speed, effort has been put into pursuing fast-switching storage devices. This has successfully produced stateof-the-art systems with picosecond timescales, although operating far (≳ 10 6 ) above the reversible limit [9][10][11][12] . On the other hand, reducing W down to the Landauer limit, at the expense of slow operation, has been beautifully demonstrated using small particles in traps 2,3 or single-domain nanomagnets 4 as envisioned by Landauer and Bennett 1,8 . All of the mentioned systems are large enough to ...

show abstract

mentioning

confidence: 99%

mentioning

confidence: 99%

mentioning

confidence: 99%

See 1 more Smart Citation

Quantum Landauer erasure with a molecular nanomagnet

et al. 2018

Self Cite

View full text Add to dashboard Cite

show abstract

“…The sample was completely covered by a non-magnetic epoxy to prevent it from moving under the action of the applied magnetic field. The alignment of − → H perpendicular (±0.05 • ) to z and close (±5 • ) to the hard x axis was done at low temperatures (T = 2 K), using the strong dependence of χ ′ (T, ω) on the magnetic field orientation (see [22] for further details). These data were scaled with measurements performed, for T 1.8 K, using a commercial SQUID magnetometer and a physical measurement platform equipped with ac susceptibility options.…”

Section: H Xmentioning

confidence: 99%

Quantum Interference Oscillations of the Superparamagnetic Blocking in anFe8Molecular Nanomagnet

et al. 2013

Self Cite

View full text Add to dashboard Cite

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

show abstract

“…The interesting point is that such decoherence is collective and brings in collective short-living spin-wave excitations in the paramagnetic state [27,28]. Recently, it was shown that Fe 8 orders magnetically below 0.6 K through long-range dipole-dipole interactions [29] implying spin-waves with much longer life-times and probable suppression of Rabi oscillations below this temperature. The microwave-field-dependent decoherence by protons in V 15 cannot be tested in these Fe 8 experiments because they were done outside the decoherence window, given in Shim et al [24].…”

Section: Rabi Oscillations and Multiple Qubit Decoherence In A Singlementioning

confidence: 99%

Mesoscopic systems: classical irreversibility and quantum coherence

Barbara

2012

Phil. Trans. R. Soc. A.

View full text Add to dashboard Cite

Mesoscopic physics is a sub-discipline of condensed-matter physics that focuses on the properties of solids in a size range intermediate between bulk matter and individual atoms. In particular, it is characteristic of a domain where a certain number of interacting objects can easily be tuned between classical and quantum regimes, thus enabling studies at the border of the two. In magnetism, such a tuning was first realized with large-spin magnetic molecules called single-molecule magnets (SMMs) with archetype Mn 12 -ac. In general, the mesoscopic scale can be relatively large (e.g. micrometre-sized superconducting circuits), but, in magnetism, it is much smaller and can reach the atomic scale with rare earth (RE) ions. In all cases, it is shown how quantum relaxation can drastically reduce classical irreversibility. Taking the example of mesoscopic spin systems, the origin of irreversibility is discussed on the basis of the Landau-Zener model. A classical counterpart of this model is described enabling, in particular, intuitive understanding of most aspects of quantum spin dynamics. The spin dynamics of mesoscopic spin systems (SMM or RE systems) becomes coherent if they are well isolated. The study of the damping of their Rabi oscillations gives access to most relevant decoherence mechanisms by different environmental baths, including the electromagnetic bath of microwave excitation. This type of decoherence, clearly seen with spin systems, is easily recovered in quantum simulations. It is also observed with other types of qubits such as a single spin in a quantum dot or a superconducting loop, despite the presence of other competitive decoherence mechanisms. As in the molecular magnet V 15 , the leading decoherence terms of superconducting qubits seem to be associated with a non-Markovian channel in which short-living entanglements with distributions of twolevel systems (nuclear spins, impurity spins and/or charges) leading to 1/f noise induce t 1 -like relaxation of S z with dissipation to the bath of two-level systems with which they interact most. Finally, let us mention that these experiments on quantum oscillations are, most of the time, performed in the classical regime of Rabi oscillations, suggesting that decoherence mechanisms might also be treated classically.

show abstract

Magnetic Dipolar Ordering and Quantum Phase Transition in anFe8Molecular Magnet

Cited by 43 publications

References 43 publications

Quantum Landauer erasure with a molecular nanomagnet

Quantum Landauer erasure with a molecular nanomagnet

Quantum Interference Oscillations of the Superparamagnetic Blocking in anFe8Molecular Nanomagnet

Mesoscopic systems: classical irreversibility and quantum coherence

Contact Info

Product

Resources

About