Landau-Zener tunneling in the presence of weak intermolecular interactions in a crystal of<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML" display="inline"><mml:msub><mml:mi mathvariant="normal">Mn</mml:mi><mml:mn>4</mml:mn></mml:msub></mml:math>single-molecule magnets

Wernsdorfer, Wolfgang; Bhaduri, Sumit; Vinslava, Alina; Christou, George

doi:10.1103/physrevb.72.214429

Cited by 51 publications

(42 citation statements)

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“…When considering only two clusters in the case of the [M n 4 ] 2 dimers, the weak exchange between M n 4 units has been found only to modify, not suppress QTM and resonance features 3 . A similar behavior is observed for M n 4 clusters weakly coupled along a chain in the presence of a partial ordering 4 . But for 3D M n 4 networks, no resonance effects were reported in the superparamagnetic blocking regime even though (incoherent) magnetic quantum tunneling could be inferred from low temperature specific heat measurements 5 .…”

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confidence: 77%

Resonant quantum tunneling of spin chains in a three-dimensional magnetically ordered state

2006

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We show that resonant quantum tunneling of the magnetization, until now observed only in zerodimensional (0D) cluster systems, occurs in the molecular Ising spin chain [(CH3)3N H]CoCl3·2H2O, which orders as a canted 3D-antiferromagnet at TC = 4.15 K. We present three features that prove unambigously the existence of resonant quantum tunneling below 0.3 K (TC/12): Temperature independent relaxation of the magnetization, speeding up of the relaxation at a well defined field (1025 Oe) and increase of the magnetization each time this field is crossed during a succession of minor hysteresis loops. A mechanism is proposed to describe the behavior based on a simple model of 0D domain wall nucleation.PACS numbers: 75.45.+j, 75.50.Xx, 75.60.Jk, 76.60.Es The existence of resonant quantum tunneling of the magnetization (QTM) for clusters of several strongly correlated spins is well established. The archetypes of these zero-dimensional (0D) systems, called single molecule magnets (SMMs), are M n 12 1 or F e 8 2 . Each cluster carries a well defined macrospin S = 10 with a large Ising like anisotropy and is weakly coupled to its neighbors. QTM is observed at low temperatures when the system displays a crossover from a thermally activated relaxation over the anisotropy barrier to a temperature independent relaxation due to tunneling through the barrier. In addition, a resonance effect occurs as a function of field at level crossings of the 2S + 1 multiplet. Recently, studies of the effect of weak dipolar and exchange interactions on tunneling have been reported. When considering only two clusters in the case of the [M n 4 ] 2 dimers, the weak exchange between M n 4 units has been found only to modify, not suppress QTM and resonance features 3 . A similar behavior is observed for M n 4 clusters weakly coupled along a chain in the presence of a partial ordering 4 . But for 3D M n 4 networks, no resonance effects were reported in the superparamagnetic blocking regime even though (incoherent) magnetic quantum tunneling could be inferred from low temperature specific heat measurements 5 . For 1D systems, the so called single chain magnet M n 2 N i shows dynamics with a quantum regime below 700 mK but an absence of resonant effects 6 . In the present letter we will show that the well known compound [(CH 3 ) 3 N H]CoCl 3 · 2H 2 O, (CoTAC), a 3D network of exchanged-coupled ferromagnetic chains, does exhibit QTM and resonance effects well below its 3D antiferromagnetic transition temperature (T C = 4.15 K). Note that there is an essential difference between this system and those previously studied since CoTAC undergoes a classic 3D phase transition. We use standard experimental procedures which have proved their effectiveness in the search for QTM and resonance effects for SMMs. We measured the absolute values of the magnetization of a single crystal of 12.2 mg by the extraction method, us- ing a superconducting quantum interference device magnetometer equipped with a miniature dilution refrigerator developed at the CRTBT, CNRS. S...

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confidence: 77%

Resonant quantum tunneling of spin chains in a three-dimensional magnetically ordered state

2006

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“…LZ transitions can be used to effectively control qubit gate operations [8,9] and to read out qubits [10]. Recently, LZ transitions have been observed in various experiments with superconducting qubits [11][12][13][14] and nanomagnets [15].Landau-Zener transitions can also occur for a qubit that is coupled to a circuit oscillator. Then, the adiabatic following to the final ground state takes place even in the absence of a direct coupling between the two qubit levels, induced instead by the indirect coupling to the c EDP Sciences…”

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Quantum state preparation in circuit QED via Landau-Zener tunneling

et al. 2006

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PACS. 32.80.Qk -Coherent control of photon-atom interactions. PACS. 03.67.Lx -Quantum computation. PACS. 32.80.Bx -Level crossing and optical pumping.Abstract. -We study a qubit undergoing Landau-Zener transitions enabled by the coupling to a circuit-QED mode. Summing an infinite-order perturbation series, we determine the exact nonadiabatic transition probability for the qubit, being independent of the frequency of the QED mode. Possible applications are single-photon generation and the controllable creation of qubit-oscillator entanglement.Superconducting loops are promising candidates for solid state qubit implementations [1][2][3][4]. Since the direct observation of Rabi-oscillations in these systems [1], they form the basis of many experiments on coherent quantum dynamics. Particularly interesting are the experiments in circuit quantum electrodynamics (QED) [2][3][4], which is the solid-state analogue of a two-level atom in an optical cavity. Superconducting circuits possess the advantage that many of their parameters are tunable over a broad range. This can be exploited for controlling efficiently the qubits.One particular way of controlling a qubit works by switching the difference of its diabatic energies from a large negative to a large positive value, yielding an avoided crossing for the adiabatic energies. For sufficiently slow switching, the qubit will adiabatically follow its instantaneous eigenstates. In the opposite limit of fast switching, however, the qubit will abandon the adiabatic eigenstate and undergo a so-called Landau-Zener (LZ) transition. The LZ transition probability can be raised upon increasing the switching rate [5][6][7]. LZ transitions can be used to effectively control qubit gate operations [8,9] and to read out qubits [10]. Recently, LZ transitions have been observed in various experiments with superconducting qubits [11][12][13][14] and nanomagnets [15].Landau-Zener transitions can also occur for a qubit that is coupled to a circuit oscillator. Then, the adiabatic following to the final ground state takes place even in the absence of a direct coupling between the two qubit levels, induced instead by the indirect coupling to the c EDP Sciences

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“…For a two-level system with a linearly time-dependent Hamiltonian, the analytically solvable Landau-Zener-Stückelberg (LZS) model [1,2,3] reflects the most important properties of the dynamics. Phenomena that can be described using this model include the dynamics of molecular vibrations [4,5], multiphoton transitions and ionization of Rydberg atoms [6,7,8,9], molecular nanomagnets [10,11,12,13] and also quantum information processing with superconducting qubits [14,15]. Multilevel and nonlinear generalizations of the LZS model have also been studied extensively (see e.g.…”

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Dynamics of periodic anticrossings: Decoherence, pointer states, and hysteresis curves

2008

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We consider a strongly driven two-level (spin) system, with a periodic external field that induces a sequence of avoided level crossings. The spin system interacts with a bosonic reservoir which leads to decoherence. A Markovian dynamical equation is introduced without relying on the rotating wave approximation in the system-external field interaction. We show that the time evolution of the two-level system is directed towards an incoherent sum of periodic Floquet states regardless of the initial state and even the type of the coupling to the environment. Analyzing the time scale of approaching these time-dependent pointer states, information can be deduced concerning the nature and strength of the system-environment coupling. The inversion as a function of the external field is usually multi-valued, and the form of these hysteresis curves is qualitatively different for low and high temperatures. For moderate temperatures we found that the series of Landau-ZenerStückelberg-type transitions still can be used for state preparation, regardless of the decoherence rate. Possible applications include quantum information processing and molecular nanomagnets.

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Landau-Zener tunneling in the presence of weak intermolecular interactions in a crystal ofMn4single-molecule magnets

Cited by 51 publications

References 59 publications

Resonant quantum tunneling of spin chains in a three-dimensional magnetically ordered state

Resonant quantum tunneling of spin chains in a three-dimensional magnetically ordered state

Quantum state preparation in circuit QED via Landau-Zener tunneling

Dynamics of periodic anticrossings: Decoherence, pointer states, and hysteresis curves

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