Improving the stability of cryogenic current comparator setups

Drung, D.; Götz, Martín; Pesel, Eckart; Storm, Jan-Hendrik; Assmann, C.; Peters, M.; Schurig, T.

doi:10.1088/0953-2048/22/11/114004

Cited by 29 publications

(30 citation statements)

References 10 publications

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“…The measurements were made with a cryogenic current comparator (CCC) bridge very similar to the one which had previously been used for a precision measurement of the Hall quantization in the fractional QHE state [19,20,21]. In that work, the lowest current level of 80 nA had allowed a measurement uncertainty of 6 parts in 10 8 .…”

Section: Resultsmentioning

confidence: 99%

Precision measurement of the quantized anomalous Hall resistance at zero magnetic field

Götz

Fijalkowski

Pesel

et al. 2018

Applied Physics Letters

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In the quantum anomalous Hall effect, the edge states of a ferromagnetically doped topological insulator exhibit quantized Hall resistance and dissipationless transport at zero magnetic field. Up to now, however, the resistance was experimentally assessed with standard transport measurement techniques which are difficult to trace to the von-Klitzing constant RK with high precision. Here, we present a metrologically comprehensive measurement, including a full uncertainty budget, of the resistance quantization of V-doped (Bi,Sb)2Te3 devices without external magnetic field. We established as a new upper limit for a potential deviation of the quantized anomalous Hall resistance from RK a value of 0.26 ± 0.22 ppm, the smallest and most precise value reported to date. This provides another major step towards realization of the zero-field quantum resistance standard which in combination with Josephson effect will provide the universal quantum units standard in the future.Quantum standards are the backbone of the system of measurement units. Already since 1990 all electrical units are based on flux quantization in units of ℎ 2 ⁄ , realized with the Josephson effect [1,2], and conductance quantization in units of 2 ℎ ⁄ , realized with the quantized Hall effect (QHE) [3,4]. With the revision of the international system of units, SI, in near future [5,6] also the realizations of the units of mass [7,8], the kilogram, and of temperature [9,10], the Kelvin, will utilize and rely on practical electric quantum standards, realizing the vision of Maxwell [11] and Planck [12] of a truly universal system of units. Both electrical quantum standards require temperatures of 4 K or lower for their operation, but since in addition the QHE only works in a magnetic field, it is practically impossible to combine both in one system. However, in ferromagnetic topological insulators like e.g. Cr-or V-doped (Bi,Sb)2Te3, the quantum anomalous Hall effect (QAHE) provides conductance quantization without a magnetic field [13][14][15][16], giving legitimate hope for a future quantum standard where all units based on ℎ and can be realized in one measurement setup.Yet, up to now the precision of the QAHE has not been tested with precision metrology methods, and in particular no uncertainty budgets were presented with the data published [17,18]. Indeed, the fact that very low measurement currents are required makes it difficult to reach uncertainties in the parts in 10 9 range as are routinely obtained in calibrations based on GaAs or graphene QHE devices. A main reason for the limitation of current is the robustness of the ferromagnetic state, which at this stage of development still requires temperatures in the mK-regime and does not tolerate current levels

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Section: Resultsmentioning

confidence: 99%

Precision measurement of the quantized anomalous Hall resistance at zero magnetic field

Götz

Fijalkowski

Pesel

et al. 2018

Applied Physics Letters

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“…The traceable calibration is performed with a state-ofthe art CCC resistance bridge developed in collaboration between PTB and the company Magnicon [9,14]. The suitability of this special setup has been experimentally proven (see chapter 3), but other CCC resistance bridges may alternatively be used if the required turns ratios are available.…”

Section: Traceable Calibrationmentioning

confidence: 99%

“…To suppress settling effects after current reversal, a certain number of data points is disregarded after each polarity change. However, beside the relatively uncritical exponential decays, slowly-decaying transients with 1/t dependence may occur that can falsify the result long after polarity reversal [14,18]. Due to lowfrequency excess noise it is not desirable to make the repetition frequency f R unnecessarily low.…”

Section: Settling After Current Reversalmentioning

confidence: 99%

Ultrastable low-noise current amplifier

Drung

Krause

Becker

et al. 2014

29th Conference on Precision Electromagnetic Measurements (CPEM 2014)

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An ultrastable low-noise current amplifier (ULCA) is presented. The ULCA is a non-cryogenic instrument based on specially designed operational amplifiers and resistor networks. It involves two stages, the first providing a 1000-fold current gain and the second performing a current-to-voltage conversion via an internal 1 MΩ reference resistor or, optionally, an external standard resistor. The ULCA's transfer coefficient is extremely stable versus time, temperature and current amplitude within the full dynamic range of ±5 nA. A low noise level of 2.4 fA/√Hz helps to keep averaging times low at small input currents. A cryogenic current comparator is used to calibrate both input current gain and output transresistance, providing traceability to the quantum Hall effect. Typically, within one day after calibration, the uncertainty contribution from short-term fluctuations of the transresistance is below one part in 10 7 . The long-term stability is expected to be better than one part in 10 5 over a year. A high-precision variant is available that shows a substantially improved stability at the expense of a higher noise level of 7.5 fA/√Hz. The ULCA also allows the traceable generation of small electrical currents or the calibration of high-ohmic resistors.

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“…It is an upgraded version of the one presented in [5]. All components including the primary current source I 1 are battery-powered and housed in a closed metallic box [6]. The resistors have nominal values of R/8 m in the range selector or R · 2 n in the 12 upper bits of the binary module with R = 10 k and natural m and n. The current I 1 flowing through the primary resistor R 1 and the corresponding CCC winding of N 1 turns, results in a voltage V X at the output (X) of amplifier Amp #1, which equals −I 1 · R/8 m with m depending on the selected range.…”

Section: A Conceptmentioning

confidence: 99%

Aspects of Application and Calibration of a Binary Compensation Unit for Cryogenic Current Comparator Setups

Drung

Götz

Pesel

et al. 2013

IEEE Trans. Instrum. Meas.

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We have developed a binary compensation unit for balancing measurement bridges with cryogenic current comparators (CCCs) commonly used in resistance metrology. We present the basic design ideas for the new microcontroller-operated module. It offers balance over a gapless range of resistance ratios of the resistors to be compared. The binary setup allows for convenient calibration when being combined with a binary CCC. The calibration can be performed using the CCC's control electronics and software. Examples of measurements demonstrate the unit's high flexibility and stability of resistance calibration well below one part in 10 9 over a period of 21 hours.

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Improving the stability of cryogenic current comparator setups

Cited by 29 publications

References 10 publications

Precision measurement of the quantized anomalous Hall resistance at zero magnetic field

Precision measurement of the quantized anomalous Hall resistance at zero magnetic field

Ultrastable low-noise current amplifier

Aspects of Application and Calibration of a Binary Compensation Unit for Cryogenic Current Comparator Setups

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