Physics
http://hdl.handle.net/10211.3/128831
Wed, 18 May 2022 00:30:29 GMT2022-05-18T00:30:29ZA quantitative study of bias triangles presented in chemical potential space
http://hdl.handle.net/10211.3/206632
A quantitative study of bias triangles presented in chemical potential space
Perron, Justin; Stewart, M. D.; Zimmerman, Neil
We 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 License
Wed, 20 May 2015 00:00:00 GMThttp://hdl.handle.net/10211.3/2066322015-05-20T00:00:00ZLong-distance correlation-length effects and hydrodynamics of 4He films in a Corbino geometry
http://hdl.handle.net/10211.3/206629
Long-distance correlation-length effects and hydrodynamics of 4He films in a Corbino geometry
Thomson, Stephen; Perron, Justin; Gasparini, Francis
Previous 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
.
Mon, 26 Sep 2016 00:00:00 GMThttp://hdl.handle.net/10211.3/2066292016-09-26T00:00:00ZA new regime of Pauli-spin blockade
http://hdl.handle.net/10211.3/206625
A new regime of Pauli-spin blockade
Perron, Justin; Stewart, M.D.; Zimmerman, Neil
Pauli-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.
Thu, 07 Apr 2016 00:00:00 GMThttp://hdl.handle.net/10211.3/2066252016-04-07T00:00:00ZValley blockade in a silicon double quantum dot
http://hdl.handle.net/10211.3/206622
Valley blockade in a silicon double quantum dot
Perron, Justin; Gullans, Michael; Taylor, Jacob; Stewart, M.D.; Zimmerman, Neil
Electrical 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.
Mon, 13 Nov 2017 00:00:00 GMThttp://hdl.handle.net/10211.3/2066222017-11-13T00:00:00Z