Relaxation dynamics in double-spin systems

Stegmann, Philipp; König, Jürgen; Sothmann, Björn

doi:10.1103/physrevb.101.075411

Cited by 11 publications

(5 citation statements)

References 68 publications

(76 reference statements)

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“…The system has a negative temperature steady state that can be regarded as a negative temperature reservoir. We hope that our result could help fabricate a hybrid system with a waveguide which has the potential to be used in quantum technologies, such as the realization of high-efficiency quantum heat engines [28][29][30][31][32][33][34][35][36][37][38], refrigerators [40][41][42][43][44][45][46], or quantum batteries [47]. Then, quantum simulation with negative temperature [48] can be explored in a hybrid system with a waveguide [49].…”

Section: Conclusion and Discussionmentioning

confidence: 91%

Negative temperature phenomena in two coupled qubit-ensembles

Han¹,

Wang²,

Li³

2022

J. Phys. B: At. Mol. Opt. Phys.

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Negative absolute temperature has wide range of applications, such as high-efficiency quantum heat engines, quantum refrigerators, and quantum simulation. In a recent paper [Phys. Rev. Lett. 120, 060403 (2018)], the authors proposed two spin ensembles coupled to the same reservoir collectively, one ensemble relaxes to negative temperature since two ensembles have unbalanced spin sizes. However, the coherent coupling mediated by the common environment is not considered. Here, we discuss negative temperature in a system where two qubit-ensembles are coupled to a same one-dimensional waveguide. In the limit of Markovian approximation, by investigating the coherent coupling and non-cross (cross) collective decay between two qubit-ensembles, we find that the duration of negative temperature state depends on the distance between two ensembles. The decrease of negative temperature duration is due to coherent coupling between two ensembles that will hybrid the unitary evolution of the system. Some optimal points produce the longest duration time of negative temperature, but it could not occur since the distance is out of the range of appropriate regions. The negative temperature sub-ensemble plays the role of a reservoir in quantum Otto heat engine, which is performed beyond the Otto limit.

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Section: Conclusion and Discussionmentioning

confidence: 91%

Negative temperature phenomena in two coupled qubit-ensembles

Han¹,

Wang²,

Li³

2022

J. Phys. B: At. Mol. Opt. Phys.

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“…Klenke & Scholler, 2015) have been supplemented by citizen science, through individual (websites, e.g. Ellis, 2020; Kruse, 2020; Lechat, 2020; Sothmann, 2020) or collective initiatives (nature platforms for the sharing of observational data about global biodiversity, e.g. Waarneming.nl, 2021).…”

Section: Discussionmentioning

confidence: 99%

“…We used a few websites and blogs written by plant pathologists (e.g. Ellis, 2020; Kruse, 2020; Lechat, 2020; Sothmann, 2020). We also used basic botanical guide books to identify the host plants, particularly for difficult groups, such as Poacea or Carex (e.g.…”

Section: Methodsmentioning

confidence: 99%

“…Unless otherwise stated, the determination was considered certain on the basis of Klenke & Scholler (2015) and Viennot-Bourgin (1949), and confirmed on the basis of information found on different websites or blogs of plant pathologists (e.g. Ellis, 2020; Kruse, 2020; Lechat, 2020; Sothmann, 2020), or comments received in conversations on Twitter. Additional references were added for species requiring further information for their identification.

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mentioning

confidence: 85%

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‘Phytopathological strolls’ in the dual context of COVID-19 lockdown and IYPH2020: transforming constraints into an opportunity for public education about plant pathogens

Suffert

2021

Preprint

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The experience presented here relates to 2020, a particularly timely year for plant disease-related communication ('International Year of Plant Health' IYPH2020), but also a unique year because of the COVID-19 pandemic. Our goal was to illustrate the diversity and beauty of fungal plant pathogens through a naturalist approach that could be followed by any amateur. We achieved this end through 'phytopathological strolls', in which we observed and determined the origin of symptoms on diseased plants found in our garden, in the local streets, in nearby open spaces, and sharing this matter with a broad public. The lockdown imposed in France created an additional motivation to take up the challenge, and to involve our children, even under strong constraints, such as movement restrictions. We observed and described fungal pathogens through hundreds of photographs, shared our findings with a large audience on Twitter, and received feedback. The material used was deliberately simple and transportable: a digital reflex camera, an old microscope, a mobile phone, some books and an Internet connexion. Between March 17 March and December 15, 2020 we found 148 plant pathogens, including 72 rusts, 22 powdery mildews and 22 septoria-like diseases. We discuss here the importance of promoting searches for plant pathogens, their description and conservation, through a combination of classical approaches and digital tools in tune with the times, such as Twitter, by treating pathogen identification like a detective game and, more surprisingly, by making use of the addictive nature of collection approaches, drawing a parallel with Pokémon Go.

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“…For example, they do not account for so-called quantum spin-transfer torque resulting due to the quantum many-body states [57] and Kondo effect [43,58], as neither is included in the effective single-particle picture of the hybrid methods. It is also questionable if they can describe the relaxation of large spins into an excited state due to the coherent coupling to reservoirs observed in quantum systems [59][60][61], although there are some examples of nonthermal steady states in quantum-classical systems [62]. In the context of our study, it is also important to note that hybrid methods tend to underestimate the damping of the magnetic nutations [45,63].…”

Section: Introductionmentioning

confidence: 99%

Nonequilibrium dynamics in a spin valve with non-collinear magnetization

Smorka¹,

Baláž²,

Thoss³

et al. 2022

Preprint

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We utilize a hybrid quantum-classical equation of motion approach to investigate the spin dynamics and spin-transfer torque in a spin valve under bias voltage. We show that the interplay between localized classical magnetic moments and conduction electrons induces a complex effective exchange coupling between the magnetic layers. This leads to a declination of magnetizations from layer anisotropy axes even in equilibrium. Introducing a finite bias voltage triggers spin currents and related spin transfer torques which further tilt the magnetizations and govern the relaxation processes of the spin dynamics. Analyzing different scenarios of the applied bias voltage, we show that symmetric and asymmetric voltage drops can lead to relaxation times of the spin dynamics that differ by several orders of magnitude at comparable charge currents. In both cases we observe resonant features, where the relaxation is boosted whenever the chemical potential of the leads matches the maxima in the density of the states of the spin-valve electrons.

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Relaxation dynamics in double-spin systems

Cited by 11 publications

References 68 publications

Negative temperature phenomena in two coupled qubit-ensembles

Negative temperature phenomena in two coupled qubit-ensembles

‘Phytopathological strolls’ in the dual context of COVID-19 lockdown and IYPH2020: transforming constraints into an opportunity for public education about plant pathogens

Nonequilibrium dynamics in a spin valve with non-collinear magnetization

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