Sub-nanosecond tuning of microwave resonators fabricated on ruddlesden–popper dielectric thin films

This is the peer reviewed version of the following article: A. M. Hagerstrom, X. Lu, N. M. Dawley, H. P. Nair, J. Mateu, R. D. Horansky, C. A. E. Little, J. C. Booth, C. J. Long, D. G. Schlom, N. D. Orloff, Adv. Mater. Technol. 2018, 3, 1800090. https://doi-org.recursos.biblioteca.upc.edu/10.1002/admt.201800090, which has been published in final form at https://doi.org/10.1002/admt.201800090. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Self-Archiving.Voltage-tunable dielectric materials are widely used for microwave-frequency signal processing. Among tunable dielectric thin films, (SrTiO3)nSrO Ruddlesden–Popper (RP) superlattices have exceptionally low loss at high frequencies. This paper reports the first realization of resonators, a ubiquitous building block of microwave components, fabricated on RP films, and an analysis of their static and dynamic tuning behavior. The RP film has a ferroelectric-paraelectric phase transition at ˜200 K, and the tunability is strongest at this temperature. The resonators have approximately 2.5% tuning of the resonance frequency at room temperature and 20% tuning at 200 K, and a tuning time scale of less than a nanosecond, which is limited by the measurement circuit rather than material properties.Peer ReviewedPostprint (author's final draft

Synchronisation in networks of delay-coupled type-I excitable systems

We use a generic model for type-I excitability (known as the SNIPER or SNIC model) to describe the local dynamics of nodes within a network in the presence of non-zero coupling delays. Utilising the method of the Master Stability Function, we investigate the stability of the zero-lag synchronised dynamics of the network nodes and its dependence on the two coupling parameters, namely the coupling strength and delay time. Unlike in the FitzHugh-Nagumo model (a model for type-II excitability), there are parameter ranges where the stability of synchronisation depends on the coupling strength and delay time. One important implication of these results is that there exist complex networks for which the adding of inhibitory links in a small-world fashion may not only lead to a loss of stable synchronisation, but may also restabilise synchronisation or introduce multiple transitions between synchronisation and desynchronisation. To underline the scope of our results, we show using the Stuart-Landau model that such multiple transitions do not only occur in excitable systems, but also in oscillatory ones.Comment: 10 pages, 9 figure

Chimera-like states in modular neural networks

Chimera states, namely the coexistence of coherent and incoherent behavior, were previously analyzed in complex networks. However, they have not been extensively studied in modular networks. Here, we consider a neural network inspired by the connectome of the C. elegans soil worm, organized into six interconnected communities, where neurons obey chaotic bursting dynamics. Neurons are assumed to be connected with electrical synapses within their communities and with chemical synapses across them. As our numerical simulations reveal, the coaction of these two types of coupling can shape the dynamics in such a way that chimera-like states can happen. They consist of a fraction of synchronized neurons which belong to the larger communities, and a fraction of desynchronized neurons which are part of smaller communities. In addition to the Kuramoto order parameter ?, we also employ other measures of coherence, such as the chimera-like ? and metastability ? indices, which quantify the degree of synchronization among communities and along time, respectively. We perform the same analysis for networks that share common features with the C. elegans neural network. Similar results suggest that under certain assumptions, chimera-like states are prominent phenomena in modular networks, and might provide insight for the behavior of more complex modular networks

Sub-nanosecond tuning of microwave resonators fabricated on ruddlesden–popper dielectric thin films

This is the peer reviewed version of the following article: A. M. Hagerstrom, X. Lu, N. M. Dawley, H. P. Nair, J. Mateu, R. D. Horansky, C. A. E. Little, J. C. Booth, C. J. Long, D. G. Schlom, N. D. Orloff, Adv. Mater. Technol. 2018, 3, 1800090. https://doi-org.recursos.biblioteca.upc.edu/10.1002/admt.201800090, which has been published in final form at https://doi.org/10.1002/admt.201800090. This article may be used for non-commercial purposes in accordance with Wiley Terms and Conditions for Self-Archiving.Voltage-tunable dielectric materials are widely used for microwave-frequency signal processing. Among tunable dielectric thin films, (SrTiO3)nSrO Ruddlesden–Popper (RP) superlattices have exceptionally low loss at high frequencies. This paper reports the first realization of resonators, a ubiquitous building block of microwave components, fabricated on RP films, and an analysis of their static and dynamic tuning behavior. The RP film has a ferroelectric-paraelectric phase transition at ˜200 K, and the tunability is strongest at this temperature. The resonators have approximately 2.5% tuning of the resonance frequency at room temperature and 20% tuning at 200 K, and a tuning time scale of less than a nanosecond, which is limited by the measurement circuit rather than material properties.Peer Reviewe