David B. Newell’s research while affiliated with National Institute of Standards and Technology and other places

... Nowadays, atom gravimeters are recognized as a significant type of high-precision absolute gravimeters, demonstrating excellent short-term sensitivity [2][3][4][5] and strong capabilities for continuous measurement with relatively high repetition rates [4,[6][7][8]. Atom gravimeters have also shown comparable accuracies in international comparisons of absolute gravimeters alongside freely-falling corner-cube gravimeters [9][10][11][12]. Comprehensive systematic evaluations are essential for absolute gravimeters [13,14]. ...

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Fast determination of the tilt of Raman lasers using the tilt-scanned fringe for atom gravimeters

... Here, we are delighted to be able to include four excellent contributions. The role of anelastic effects in flexure mechanisms for precision metrological systems, such a Kibble balances, was analysed by Keck et al [1] in a joint submission from the United States National Institute of Standards and Technology (NIST) and TU Ilmenau. In a further joint paper by NIST and TU Ilmenau, Schulze et al [2] propose the use of an electrostatic force balance to improve the realization and dissemination of radionuclide activity. ...

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Precision measurement and engineering at the 60th Ilmenau Scientific Colloquium

... Large domains of low-energy stacking and small nodes of high-energy stacking emerge, while so-called stacking solitons connect the nodes and separate the low-energy domains. The relative size of the domains is given by the relative energy of the high-symmetry stackings, delicately balanced with the strain energy necessary to form the solitons [13,14]. The quantitative theoretical assessment of the domain energy and interlayer distance therefore is crucial to correctly model the domain reconstruction of twisted homoand heterobilayers. ...

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Precise structure and energy of group 6 transition metal dichalcogenide homo- and heterobilayers in high-symmetry configurations

... The effect is characterized by a universal electrical conductance that is quantized to e 2 /h, where e is the elementary charge and h is the Planck constant. This quantization persists even at zero external magnetic field and could be of use in quantum resistance metrology [16][17][18][19][20] . ...

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A balanced quantum Hall resistor

... This functionalization process helps to maintain the device's electrical properties over an extended period of time and introduces the required disorder for the desired transition. The resulting device is a high-quality, tunable carrier-density graphene device that has been specifically developed for use in quantum Hall resistance standard array devices [37][38][39][40][41]. To vary the carrier density of our graphene device, we use low-temperature light illumination instead of using the vacuum gentle heating technique, which is suitable for a small-sample-space He 4 cryostat [37]. ...

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Direct insulator to relativistic quantum Hall transition in graphene

... This process of establishment is called individual realization of the kilogram. However, at present, the dissemination of the kilogram based on individual realizations is not internationally approved owing to the inconsistency among the individual realizations by NMIs [6]. The traceability of the primary mass standards of the NMIs to h is therefore presently ensured not by the individual realizations but by the consensus value of the kilogram (CV) [7,8]. ...

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Evaluation of the long-term reproducibility of a realization of the kilogram by the XRCD method

... Instead, it is used to calibrate a conventional resistor. A notable exception is a recent publication that describes a single circuit with both quantum standards and the Kibble balance [26]. ...

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Thoughts on the Kibble–Robinson theory

... Interestingly, the slope of the experimental power dependence (~1 nA μW −1 ) significantly exceeds this estimate. As we discuss in more detail below, the PC signal also shows a strong gate voltage dependence owing to relaxation effects, and the experimental values are taken at local PC difference maxima, where significant carrier multiplication can be expected 27 . In addition, the donut-shaped intensity profile of the light, not taken into account in the estimate, enhances the current flow into the outer contact. ...

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Optical pumping of electronic quantum Hall states with vortex light

... The quantum anomalous Hall effect (QAHE), characterized by a quantized Hall effect and a vanishing longitudinal resistance at zero magnetic field, is an example of a topologically protected state of matter [1]. Although the QAHE has potential applications in metrology [2,3] as well as classical [4][5][6][7] and quantum information processing [8], experimental realizations of the QAHE remain limited to cryogenic temperatures and low bias currents. Understanding the microscopic origin of these limitations to the QAHE is therefore crucial for realizing a robust QAHE at higher temperatures and bias currents. ...

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Visualizing the breakdown of the quantum anomalous Hall effect

... This functionalization process helps to maintain the device's electrical properties over an extended period of time and introduces the required disorder for the desired transition. The resulting device is a high-quality, tunable carrier-density graphene device that has been specifically developed for use in quantum Hall resistance standard array devices [37][38][39][40][41]. To vary the carrier density of our graphene device, we use low-temperature light illumination instead of using the vacuum gentle heating technique, which is suitable for a small-sample-space He 4 cryostat [37]. ...

Reference:

Direct insulator to relativistic quantum Hall transition in graphene