Role of coherence in transport through engineered atomic spin devices

Shakirov, Alexey M.; Shchadilova, Yulia E.; Rubtsov, A. N.; Ribeiro, Pedro

doi:10.1103/physrevb.94.224425

Cited by 14 publications

(34 citation statements)

References 64 publications

(128 reference statements)

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“…To capture spin-torque effects, we employ a masterequation description for the evolution of the reduced density matrix of the local moment that crucially includes the coherences. Therefore, we generalized the Redfield master equation approach, previously used to model coherent evolution and transport in engineered atomic spin devices [20,23], to deal with the ac driving bias.…”

Section: Model and Methodsmentioning

confidence: 99%

Spin transfer torque induced paramagnetic resonance

2019

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We show how the spin-transfer torque generated by an ac voltage may be used to excite a paramagnetic resonance of an atomic spin deposited on a metallic surface. This mechanism is independent of the environment of the atom and may explain the ubiquity of the paramagnetic resonance reported by Baumann et al. [Science 350, 417 (2015)]. The current and spin dynamics are modeled by a time-dependent Redfield master equation generalized to account for the periodic driven voltage. Our approach shows that the resonance effect is a consequence of the nonlinearity of the coupling between the magnetic moment and the spin-polarized current which generates a large second-harmonic amplitude that can be measured in the current signal.

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Section: Model and Methodsmentioning

confidence: 99%

Spin transfer torque induced paramagnetic resonance

2019

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“…with ρ M from (8). Naturally, this unique state does have the same symmetries as the Lindblad generator, since P (M) is a symmetric distribution.…”

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confidence: 94%

“…The Dicke model, for example, can be realized for a wide range of parameters covering different phases of the system [6,7]. Similar models are studied in the context of quantum magnetism [8][9][10]. Experiments are often performed under interesting non-equilibrium conditions where the interplay of driving and dissipation determines a stationary state of the system in absence of detailed balance [11][12][13].…”

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confidence: 99%

“…Following the proposals in [14,26] this model could be realized experimentally with cold atoms. Interestingly, in theoretical models for engineered atomic spin devices used to describe tunneling spectroscopy of atomic magnets on metallic surfaces, a similar GKSL dissipator appears naturally [8][9][10]. A phase diagram of this model was examined in [10].…”

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confidence: 99%

“…In order to correctly understand the phase transition, the order of limits has to be interchanged. Neglecting the 1/j-terms, as in (4), corresponds to first taking the strict thermodynamic limit leading to the family of steady states (8). Naively computing the steady state of (1) for finite j results always in a unique steady state and the broken symmetry is not revealed.…”

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confidence: 99%

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Revealing the nature of nonequilibrium phase transitions with quantum trajectories

2019

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A damped and driven collective spin system is analyzed by using quantum state diffusion. This approach allows for a mostly analytical treatment of the investigated non-equilibrium quantum many body dynamics, which features a phase transition in the thermodynamical limit. The exact results obtained in this work, which are free of any finite size defects, provide a complete understanding of the model. Moreover, the trajectory framework gives an intuitive picture of the two phases occurring, revealing a spontaneously broken symmetry and allowing for a qualitative and quantitative characterization of the phases. We determine exact critical exponents, investigate finite size scaling, and explain a remarkable non-algebraic behaviour at the transition in terms of torus hopping.

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Harnessing the Quantum Behavior of Spins on Surfaces

2022

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out via microwave photons. [4] Spins in solid-state materials constitute another family of individual quantum systems where spin states with naturally quantized energy levels can be manipulated via magnetic fields. Physical realizations of solidstate spin systems include gate-defined quantum dots, single dopants in semiconductors such as phosphorus donors in silicon, and single defects in insulators such as nitrogen-vacancy centers in diamond. [5][6][7] Harnessing quantum resources at the nanoscale gives birth to the discipline of quantum-coherent nanoscience that may bring forth useful quantum nanodevices "at the bottom." [8,9] In this review, we focus on a new class of quantum spin systems, individual atomic and molecular spins on surfaces, which has the potential to produce quantum functionalities at the atomic scale. An STM is used to access this tiny length scale, where a sharp metallic tip is positioned in nanometer proximity to spin carriers on a surface to probe their properties through tunneling electrons. [10] Experiments with single atomic spins on material surfaces date back to the early days of low-temperature STM, when Yu-Shiba-Rusinov states and a Kondo resonance were measured in individual magnetic atoms on bulk superconductors [11] and noble metals, [12,13] respectively. STM has also been extensively used on single molecular spins to characterize molecular structures, [14][15][16] probe and modify their electronic and magnetic properties, [17][18][19] and investigate their classical and quantum applications. [19][20][21] Following early STM experiments on single spins, the desire to further control and magnetically image individual spins has prompted the developments of new local probe techniques such as spinpolarized STM, [22] inelastic-tunneling-based spin-flip spectroscopy, [23] electrical pump-probe measurements, [24] and various innovative forms of force and magnetic microscopy. [25][26][27][28] An exciting development in recent years is the incorporation of coherent spin control in atomic-scale microscopy. The need to coherently manipulate and measure individual spins at this length scale necessitates all-electrical protocols with Angstrom precision. These stringent requirements are met by drawing on powerful methodologies from material and quantum sciences, that is, STM's abilities to build nanostructures atom-by-atom and selectively sense individual spin-carrying atoms, as well as electron spin resonance's (ESR's) ability to coherently control electron spin states via electromagnetic waves. This unique combination has so far enabled the quantum control of single electron spins of atoms [29][30][31][32][33] and molecules, [34] as well as the manipulation of single nuclear spins through hyperfine interactions. [35] Quantum coherence can be increased using singlet-triplet The desire to control and measure individual quantum systems such as atoms and ions in a vacuum has led to significant scientific and engineering developments in the past decades that form the basis of today's quantum infor...

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Role of coherence in transport through engineered atomic spin devices

Cited by 14 publications

References 64 publications

Spin transfer torque induced paramagnetic resonance

Spin transfer torque induced paramagnetic resonance

Revealing the nature of nonequilibrium phase transitions with quantum trajectories

Harnessing the Quantum Behavior of Spins on Surfaces

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