83 research outputs found
A quantitative study of bias triangles presented in chemical potential space
No full textWe present measurements of bias triangles in several biasing configurations. Using a capacitive model and two fit parameters we are able to predict the shapes and locations of the bias triangles in all measurement configurations. Furthermore, analysis of the data using this model allows us to present data from all four possible bias configurations on a single plot in chemical potential space. This presentation allows comparison between different biasing directions to be made in a clean and straightforward manner. Our analysis and presentation will prove useful in demonstrations of Pauli-spin blockade where comparisons between different biasing directions are paramount. The long term stability of the CMOS compatible Si/SiO2 only architecture leads to the success of this analysis. We also propose a simple variation to this analysis that will extend its use to systems lacking the long term stability of these devices. Justin K Perron, M D Stewart Jr, and Neil M Zimmerman. A quantitative study of bias triangles presented in chemical potential space, Journal of Physics: Condensed Matter, 27, (23), 235302 (2015). Creative Commons Attribution Non-Commercial No Derivatives LicenseJustin K Perron, M D Stewart Jr, and Neil M Zimmerman. A quantitative study of bias triangles presented in chemical potential space, Journal of Physics: Condensed Matter, 27, (23), 235302 (2015)0953-898
Long-distance correlation-length effects and hydrodynamics of 4He films in a Corbino geometry
No full textPrevious measurements of the superfluid density ρs and specific heat for 4He have identified effects that are manifest at distances much larger than the correlation length ξ3D [1–3]. We report here new measurements of the superfluid density which are designed to explore this phenomenon further. We determine the superfluid fraction ρs/ρ from the resonance of 34 nm films of varying widths 4 ≤ W ≤ 100 µm. The films are formed across a Corbino ring separating two chambers where a thicker 268 nm film is formed. This arrangement is realized using lithography and direct Si-wafer bonding. We identify two effects in the behavior of ρs/ρ : one is hydrodynamic, for which we present an analysis; and the other, a correlation-length effect which manifests as a shift in the transition temperature Tc relative to that of a uniform 34 nm film uninfluenced by proximity effects. We find that one can collapse both ρs/ρ and the quality factor of the resonance onto universal curves by shifting Tc as ∆Tc ∼ W−ν. This new scaling is a surprising result on two counts: it involves a very large length scale W relative to the magnitude of ξ3D; and, the dependence on W is not what is expected from correlation-length finite-size scaling which would predict ∆Tc ∼ W−1/ν .Stephen R. D. Thomson, Justin K. Perron, and Francis M. Gasparini. Long-distance correlation-length effects and hydrodynamics of He 4 films in a Corbino geometry, Physical Review B, 94, 094520 (2016).2469-995
Perron-Frobenius theorem for nonnegative tensors
No full textWe generalize the Perron-Frobenius Theorem for nonnegative matrices to the class of nonnegative tensors.Mathematics, AppliedSCI(E)88ARTICLE2507-520
Linear convergence of the Collatz method for computing the Perron eigenpair of primitive dual number matrix
No full textVery recently, Qi and Cui extended the Perron-Frobenius theory to dual number
matrices with primitive and irreducible nonnegative standard parts and proved
that they have Perron eigenpair and Perron-Frobenius eigenpair. The Collatz
method was also extended to find Perron eigenpair. Qi and Cui proposed two
conjectures. One is the k-order power of a dual number matrix tends to zero if
and only if the spectral radius of its standard part less than one, and another
is the linear convergence of the Collatz method. In this paper, we confirm
these conjectures and provide theoretical proof. The main contribution is to
show that the Collatz method R-linearly converges with an explicit rate.Comment: arXiv admin note: text overlap with arXiv:2306.16140 by other author
Great Expectatrics: Great Papers, Great Journals, Great Econometrics
No full textThe paper discusses alternative Research Assessment Measures (RAM), with an emphasis on the Thomson Reuters ISI Web of Science database (hereafter ISI). The various ISI RAM that are calculated annually or updated daily are defined and analysed, including the classic 2-year impact factor (2YIF), 5-year impact factor (5YIF), Immediacy (or zero-year impact factor (0YIF)), Eigenfactor score, Article Influence, C3PO (Citation Performance Per Paper Online), h-index, Zinfluence, and PI-BETA (Papers Ignored - By Even The Authors). The ISI RAM data are analysed for 8 leading econometrics journals and 4 leading statistics journals. The application to econometrics can be used as a template for other areas in economics, for other scientific disciplines, and as a benchmark for newer journals in a range of disciplines. In addition to evaluating high quality research in leading econometrics journals, the paper also compares econometrics and statistics, alternative RAM, highlights the similarities and differences in alternative RAM criteria, finds that several ISI RAM capture similar performance characteristics for the leading econometrics and statistics journals while the new PI-BETA criterion is not highly correlated with any of the other ISI RAM, and hence conveys additional information regarding ISI RAM, highlights major research areas in leading journals in econometrics, and discusses some likely future uses of RAM.Research assessment measures, impact factors, Immediacy, Eigenfactor score, Article influence, h-index, C3PO, Zinfluence, PI-BETA
Great Expectatrics: Great Papers, Great Journals, Great Econometrics
No full textThe paper discusses alternative Research Assessment Measures (RAM), with an emphasis on the Thomson Reuters ISI Web of Science database (hereafter ISI). The various ISI RAM that are calculated annually or updated daily are defined and analysed, including the classic 2-year impact factor (2YIF), 5-year impact factor (5YIF), Immediacy (or zero-year impact factor (0YIF)), Eigenfactor score, Article Influence, C3PO (Citation Performance Per Paper Online), h-index, Zinfluence, and PI-BETA (Papers Ignored - By Even The Authors). The ISI RAM data are analysed for 8 leading econometrics journals and 4 leading statistics journals. The application to econometrics can be used as a template for other areas in economics, for other scientific disciplines, and as a benchmark for newer journals in a range of disciplines. In addition to evaluating high quality research in leading econometrics journals, the paper also compares econometrics and statistics, alternative RAM, highlights the similarities and differences in alternative RAM criteria, finds that several ISI RAM capture similar performance characteristics for the leading econometrics and statistics journals while the new PI-BETA criterion is not highly correlated with any of the other ISI RAM, and hence conveys additional information regarding ISI RAM, highlights major research areas in leading journals in econometrics, and discusses some likely future uses of RAM.Research assessment measures; impact factors; Immediacy; Eigenfactor score; Article influence; h-index; C3PO; Zinfluence; PI-BETA
Valley blockade in a silicon double quantum dot
No full textElectrical transport in double quantum dots (DQDs) illuminates many interesting features of the dots' carrier states. Recent advances in silicon quantum information technologies have renewed interest in the valley states of electrons confined in silicon. Here we show measurements of dc transport through a mesa-etched silicon double quantum dot. Comparing bias triangles (i.e., regions of allowed current in DQDs) at positive and negative bias voltages we find a systematic asymmetry in the size of the bias triangles at the two bias polarities. Asymmetries of this nature are associated with blocked tunneling events due to the occupation of a metastable state. Several features of our data lead us to conclude that the states involved are not simple spin states. Rather, we develop a model based on selective filling of valley states in the DQD that is consistent with all of the qualitative features of our data.Justin K. Perron, Michael J. Gullans, Jacob M. Taylor, M. D. Stewart, Jr., and Neil M. Zimmerman. Valley blockade in a silicon double quantum dot, Physical Reveiw B, 96, 205302 Published 13 November (2017).2469-995
AC signal characterization for optimization of a CMOS single-electron pump
No full textPumping single electrons at a set rate is being widely pursued as an electrical current standard. Semiconductor charge pumps have been pursued in a variety of modes, including single gate ratchet, a variety of 2-gate ratchet pumps, and 2-gate turnstiles. Whether pumping with one or two AC signals, lower error rates can result from better knowledge of the properties of the AC signal at the device. In this work, we operated a CMOS single-electron pump with a 2-gate ratchet style measurement and used the results to characterize and optimize our two AC signals. Fitting this data at various frequencies revealed both a difference in signal path length and attenuation between our two AC lines. Using this data, we corrected for the difference in signal path length and attenuation by applying an offset in both the phase and the amplitude at the signal generator. Operating the device as a turnstile while using the optimized parameters determined from the 2-gate ratchet measurement led to much flatter, more robust charge pumping plateaus. This method was useful in tuning our device up for optimal charge pumping, and may prove useful to the semiconductor quantum dot community to determine signal attenuation and path differences at the device.Murray, R., Perron, J., Stewart, M. and Zimmerman, N. (2018). AC signal characterization for optimization of a CMOS single-electron pump. Nanotechnology, 29 (6), 0652020957-448
A new regime of Pauli-spin blockade
No full textPauli-spin blockade (PSB) is a transport phenomenon in double quantum dots that allows for a type of spin to charge conversion often used to probe fundamental physics such as spin relaxation and singlet-triplet coupling. In this paper, we theoretically explore Pauli-spin blockade as a function of magnetic field B applied parallel to the substrate. In the well-studied low magnetic field regime, where PSB occurs in the forward (1, 1) → (0, 2) tunneling direction, we highlight some aspects of PSB that are not discussed in detail in existing literature, including the change in size of both bias triangles measured in the forward and reverse biasing directions as a function of B. At higher fields, we predict a crossover to “reverse PSB” in which current is blockaded in the reverse direction due to the occupation of a spin singlet as opposed to the traditional triplet blockade that occurs at low fields. The onset of reverse PSB coincides with the development of a tail like feature in the measured bias triangles and occurs when the Zeeman energy of the polarized triplet equals the exchange energy in the (0, 2) charge configuration. In Si quantum dots, these fields are experimentally accessible; thus, this work suggests a way to observe a crossover in magnetic field to qualitatively different behavior. This article may be downloaded for personal use only. Any other use requires prior permission of the author and AIP Publishing. The following article appeared in Journal of Applied Physics and may be found at https://doi.org/10.1063/1.4945393.Journal of Applied Physics 119, 134307 (2016); https://doi.org/10.1063/1.49453930021-897
Purchasing Power Parity in an Emerging Market Economy: A Long-Span Study for Chile.
No full textRecent research has found evidence that supports the purchasing power parity (PPP) condition in developed countries using very long-span data, while evidence for developing countries is almost nonexistent. This paper tries to fulfill this void by testing the validity of PPP as a long run equilibrium condition for Chile, using data, since its birth as a nation, developed by Díaz, Lüders and Wagner (2003). A battery of unit-root and cointegration tests is applied. We found evidence in favor of PPP. Results are robust to changes in the domestic price index, to changes in the sample period, and to the econometric technique applied.
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