Industrial feasibility test of a graphene-enabled turnkey quantum resistance system

基准：初级电阻计量的最低要求是测量量子霍尔电阻，以优于十亿分之一（或1 nanoOhm/Ohm）。当使用传统的GaAs/AlGaAs异质结构或Si MOSFET时，这需要通过器件的至少25微安的测量电流，而不会击穿量子霍尔效应。为了实现这一点，温度必须低于1开尔文和磁场约10特斯拉或更高，以实现鲁棒的朗道量化。石墨烯的好处：石墨烯在几个方面对此进行了改进：首先，朗道量子化本质上要强得多（在10 T时为5倍）。其次，由于特定的声子谱和电子-声子耦合强度，石墨烯中热载流子的弛豫比GaAs快10倍，导致更大的击穿电流。这两种独特的石墨烯性质的组合意味着可以构建上级量子霍尔电阻。然而，到目前为止，这些影响已经在学术研究和国家物理实验室的先进实验室条件下得到了证明。有针对性的改进：该项目的挑战是将这些结果向前推进，并使这些测量在一个简单的交钥匙无致冷剂磁传输系统中成为常规。具体而言，该项目需要解决无制冷剂脉冲管冷却器中产生的噪声水平，在极低载流子密度下控制载流子密度和均匀性，以及在计量实验室外执行ppb级测量的能力。

Benchmark: The minimum requirement for primary resistance metrology is to measure the quantum Hall resistance to better than 1 part per billion (or 1 nanoOhm/Ohm). When using traditional GaAs/AlGaAs heterostructues or Si MOSFETs this requires a measurement current of at least 25 microamps through the device without breakdown of the quantum Hall effect. To achieve this the temperature must be below 1 kelvin and the magnetic field around 10 tesla or higher to achieve robust Landau quantisation. Benefit of graphene: Graphene improves on this in several ways: firstly the Landau quantisation is intrinsically much stronger (factor of 5 at 10 T). Secondly, because of the specific phonon spectrum and electron-phonon coupling strength the relaxation of hot carriers in graphene is 10 times faster than in GaAs, resulting in a much larger breakdown current. The combination of these two unique graphene properties mean that a superior quantum Hall resistance can be constructed. However, so far these effects have been demonstrated in academic research and the advanced laboratory conditions at the National Physical Laboratory. Targetted improvement: The challenge of this project to take these results forwards and make these measurements routine in a simple turn-key cryogen-free magneto-transport system. Specifically the project needs to address the noise levels produced in cryogen-free pulse-tube coolers, the control of the charge carrier density and homogeneity at very low carrier densities, and ability to perform ppb-level measurements outside metrology laboratory.