A novel double-shielding technique for ac quantum Hall measurement

Kibble, B P; Schurr, J.

doi:10.1088/0026-1394/45/5/n01

Cited by 34 publications

(35 citation statements)

References 6 publications

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“…Strictly speaking, it is the dissipation factor of parasitic capacitances which can lead to frequency-dependent deformations of the QHR plateaus and to deviations from the quantized dc resistance value. To eliminate the influence of these parasitic capacitances in the case of GaAs devices, a double-shielding method and an alternative extrapolation method had been developed to achieve an uncertainty comparable to dc resistance calibrations [13,14]. Both methods are elaborate and therefore not widely used.…”

mentioning

confidence: 99%

Towards a graphene-based quantum impedance standard

Kalmbach

Schurr

Ahlers

et al. 2014

Applied Physics Letters

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Precision measurements of the quantum Hall resistance with alternating current (ac) in the kHz range were performed on epitaxial graphene in order to assess its suitability as a quantum standard of impedance. The quantum Hall plateaus measured with alternating current were found to be flat within one part in 10 7 . This is much better than for plain GaAs quantum Hall devices and shows that the magnetic-fluxdependent capacitive ac losses of the graphene device are less critical. The observed frequency dependence of about -8×10 -8 /kHz is comparable in absolute value to the positive frequency dependence of plain GaAs devices, but the negative sign is attributed to stray capacitances which we believe can be minimized by a careful design of the graphene device. Further improvements thus may lead to a simpler and more user-friendly quantum standard for both resistance and impedance.Graphene is probably the most fascinating electronic material discovered in the last decades [1][2][3]. Among its various unique properties, an anomalous 'half-integer' quantum Hall effect (QHE) is most interesting for metrology, where the fact that the Hall resistance is quantized and depends only on fundamental constants is utilized for the representation and maintenance of the resistance unit, the ohm. Typically, twodimensional electron systems (2DES) realized in GaAs/AlGaAs heterostructures [4] are used for this purpose. The required relative measurement uncertainty of better than 1 part in 10 8 is, however, only obtained at strong magnetic fields around 10 tesla and at temperatures of 1.4 kelvin and below. In contrast, in graphene the cyclotron energy splitting between the Landau levels (which is the main factor determining the robustness of the quantized Hall resistance (QHR)) is so large that fingerprints of the QHE are even observed at room temperature [5]. Thus, with graphene a highly precise QHR standard working at low magnetic fields and temperatures above 4 kelvin is conceivable, which would be an enormous advantage for practical metrology. In fact, when measuring with direct current (dc), it has been demonstrated already that the precision of the QHE in high quality graphene devices matches that of GaAs devices [6][7][8][9]. However, in the forthcoming fundamental constant-based redefinition of the Système International d'Unités (SI) [10], also the impedance units (capacitance and inductance) will be traced to fundamental constants [11]. The most direct way to represent the impedance units is to use a quantum Hall resistance measured with alternating current (ac QHR). This has two advantages. Firstly, deriving the resistance and impedance units from the same quantum effect improves the consistency of the SI. And secondly, using the same QHE device at dc and at ac in one and the same cryomagnetic system would constitute a practical and economical advantage. Therefore, the question naturally arises whether graphene can replace GaAs also in the realm of impedance units, leading to an at least equally precise, but more userfriendl...

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confidence: 99%

Towards a graphene-based quantum impedance standard

Kalmbach

Schurr

Ahlers

et al. 2014

Applied Physics Letters

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“…The residual linear frequency dependence of all the different double-shielded QHR devices lie in an interval of ±1.8 × 10 −9 kHz −1 , which is somewhat better than the estimation given in [2]. The uncertainties of the linear least-square fits are 1.3×10 −9 kHz −1 (k = 1).…”

Section: Experimental Results Of Real Devicesmentioning

confidence: 54%

“…A simple and highly efficient technique for minimizing these effects is based on two rectangular shields surrounding the quantum Hall device, as shown in Figure 1 [2]. The two shields are arranged with a narrow gap between them in such a way that the electrical mid-plane between the shields goes through the defining Hall potential contacts and is perpendicular to the two-dimensional electron gas (2DEG).…”

Section: Introductionmentioning

confidence: 99%

A quantum impedance standard having an insignificant, experimentally verified frequency dependence

et al. 2010

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Recently we have published a novel double-shield configuration of quantum Hall devices to eliminate the effect of all presently known ac losses within 3×10 −9 kHz −1 . Now we have further verified the double-shielding technique by supporting the experimental findings with a model. This model indicates that it should be possible to reduce the frequency dependence to less than 1×10 −9 kHz −1 , which would be better than our ultimate measuring limit and much better than our calculable impedance artefacts. Thereby, the ac quantum Hall impedance closely approaches a perfect quantum standard.

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“…Kibble and Schurr have demonstrated the double-shielded ac quantized Hall resistance (QHR) device becomes independent of frequency and current within a relative uncertainty of less than 1 × 10 -8 [1]. In this "double-shielded configuration", the Hall bar is surrounded by two rectangular shields with a center narrow gap perpendicular to the Hall bar.…”

Section: Introductionmentioning

confidence: 99%

Investigation of on-chip double-shieled QHR device in ac regime

Kaneko

Schurr

Ahlers

et al. 2012

2012 Conference on Precision Electromagnetic Measurements

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For the investigation of ac performance, two onchip double-shielded QHR devices and two double-shielded chip carriers were fabricated at National Metrology Institute of Japan and have been studied with ac at Physikalisch-Technische Bundesanstalt. It has been measured that the shape of the i = 2 plateaux at zero shield-potential is not flat and the linear frequency dependence of the quantum Hall resistance amounts to -0.14 (μΩ/Ω) /kHz. Deferent shield designs are proposed to reduce the frequency dependence.

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A novel double-shielding technique for ac quantum Hall measurement

Cited by 34 publications

References 6 publications

Towards a graphene-based quantum impedance standard

Towards a graphene-based quantum impedance standard

A quantum impedance standard having an insignificant, experimentally verified frequency dependence

Investigation of on-chip double-shieled QHR device in ac regime

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