Imaging quantum fluctuations near criticality

Kremen, Anna; Khan, Hasan M.; Loh, Yen Lee; Baturina, T. I.; Trivedi, Nandini; Frydman, A.; Kalisky, Beena

doi:10.1038/s41567-018-0264-z

Cited by 20 publications

(19 citation statements)

References 33 publications

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“…In our case the out-of-phase component is itself "noisy" in the metastable domains, which is highly unusual and is probably a reflection of some magnetic frustration in the magnetic state. To the best of our knowledge the only case where susceptibility was found to be fluctuating is a system exhibiting superconductor to insulator transition, with slow quantum fluctuations in the diamagnetism [50] . We speculate that the two material systems might be related through the role of frustration: frustration in the lattice of spins in the magnetic system and frustration in the superconducting vortices in the superconducting system.…”

Section: Discussionmentioning

confidence: 99%

Picoscale Magnetoelasticity Governs Heterogeneous Magnetic Domains in a Noncentrosymmetric Ferromagnetic Weyl Semimetal

Franklin

Jayakody

et al. 2021

Adv Quantum Tech

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Magnetic Weyl semimetals are predicted to host emergent electromagnetic fields at heterogeneous strained phases or at the magnetic domain walls. Tunability and control of the topological and magnetic properties are crucial for revealing these phenomena, which are not well understood or fully realized yet. Here, a scanning superconducting quantum interference device microscope is used to image spontaneous magnetization and magnetic susceptibility of CeAlSi, a noncentrosymmetric ferromagnetic Weyl semimetal candidate. Large metastable domains are observed alongside stable ferromagnetic domains. The metastable domains most likely embody a type of frustrated or glassy magnetic phase, with excitations that may be of an emergent and exotic nature. Evidence is found that the heterogeneity of the two types of domains arises from magnetoelastic or magnetostriction effects. It is shown how these domains form, how they interact, and how they can be manipulated or stabilized with lattice strains estimated to be on picometer levels. This knowledge can be used in designing and fabricating devices made from CeAlSi and related materials for magnetic field sensing and magnetic memory applications.

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Section: Discussionmentioning

confidence: 99%

Picoscale Magnetoelasticity Governs Heterogeneous Magnetic Domains in a Noncentrosymmetric Ferromagnetic Weyl Semimetal

Franklin

Jayakody

et al. 2021

Adv Quantum Tech

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“…This broadening of the temperature range of χ(r) fluctuations was recently observed in scanning SQUID experiments of the thin film superconductor NbTiN. 23 In the experiment, a scanning SQUID was used to directly image the local χ(r) and the corresponding standard deviation as a function of temperature and film thickness was found to qualitatively match that of theory. Importantly, this was the first time quantum fluctuations were directly imaged in an experiment.…”

Section: Asmentioning

confidence: 54%

Local spectroscopies across the superconductor-insulator transition

Khan

Trivedi

2019

Phys. Rev. B

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We explore the manifestation of quantum fluctuations across the superconductor-insulator transition (SIT) in three different local measurements: the two-particle density of states P (r, ω), compressibility κ(r), and diamagnetic susceptibility χ(r). We perform Monte Carlo simulations on the 2D quantum Josephson junction array model and present local maps of these quantities as the system is tuned across the SIT. P (r, ω), obtained using Maximum Entropy analytic continuation techniques, shows strongly diminished zero-energy spectral weight in nearly-insulating islands, that also correlate with regions of suppressed κ(r). We investigate the signatures of quantum fluctuations in the evolution of κ(r) and χ(r) across the SIT, distinct from thermal fluctuations. We discuss the experimental implications of our results for scanning Josephson spectroscopy, compressibility, and scanning SQUID measurements. arXiv:1812.06954v3 [cond-mat.supr-con]

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“…[47]). Another possible source of slow dynamics may be twolevel systems, which have already been observed [48,49] in similar disordered SC films. It would be interesting, though experimentally challenging, to control the relaxation rate and check the predictions of our theory, showing, for example, the suppression of the hysteretic behavior for a short relaxation time.…”

Section: Discussionmentioning

confidence: 82%

Hysteresis and jumps in the I-V curves of disordered two-dimensional materials

Kasirer,

Meir

2021

Preprint

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The superconductor-insulator transition (SIT) in thin-film disordered superconductors is a hallmark example of a quantum phase transition. Despite being observed more than 30 years ago, its nature is still under a vivid debate. One intriguing observations concerns the insulating side of the transition, which exhibits some unusual properties. Among them is its current-voltage relation (I − V curve), which includes (1) a conductance that changes abruptly by several orders of magnitude with increasing voltage, (2) hysteretic behavior, and (3) multiple (sometimes more than a hundred) smaller current jumps near the transition. Some models have been suggested before, but no model has been successful in accounting for the observed behavior in full. One commonly used approach is to model the disordered sample as a two-dimensional array of conducting islands, where charge carriers tunnel from one island to its neighbors. In those models, fast relaxation is assumed, and the system is treated as always being in electrostatic and thermal equilibrium. Those models are successful in explaining some measurement results, including the phase transition itself, but fail to reproduce hysteresis in their predicted I − V curves. Here, we suggest incorporating finite relaxation time into an array model. We show that, in the slow relaxation limit, our model can reproduce hysteresis and multiple jumps in the I − V curve. Based on our results we argue that a similar behavior should be also observed in two-dimensional normal (non-superconducting) arrays. This claim is supported by past observations. We analyse the role of different parameters in our model, determine the range of relevant time scales in the problem, and compare our results with selected measurements.

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Imaging quantum fluctuations near criticality

Cited by 20 publications

References 33 publications

Picoscale Magnetoelasticity Governs Heterogeneous Magnetic Domains in a Noncentrosymmetric Ferromagnetic Weyl Semimetal

Picoscale Magnetoelasticity Governs Heterogeneous Magnetic Domains in a Noncentrosymmetric Ferromagnetic Weyl Semimetal

Local spectroscopies across the superconductor-insulator transition

Hysteresis and jumps in the I-V curves of disordered two-dimensional materials

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