Abstract
We report on nonreciprocity observations in several configurations of graphene-based quantum Hall devices. Two distinct measurement configurations were adopted to verify the universality of the observations (i.e., two-terminal arrays and four-terminal devices). Our findings determine the extent to which epitaxial graphene anisotropies contribute to the observed asymmetric Hall responses. The presence of backscattering induces a device-dependent asymmetry rendering the Onsager-Casimir relations limited in their capacity to describe the behavior of such devices, except in the low-field classical regime and the fully quantized Hall state. The improved understanding of this quantum electrical process broadly limits the applicability of the reciprocity principle in the presence of quantum phase transitions and for anisotropic two-dimensional materials.
Highlights
It is widely known that graphene exhibits a variety of unique properties [1,2,3,4]
In certain forms, including epitaxial graphene (EG) grown on 4H-SiC, this versatile material has been identified as a practical way to develop resistance standards based on a robust quantum Hall effect (QHE) that appears over a useable range of magnetic fields (B fields), with the key feature being a well-quantized and extended resistance plateau [5,6,7,8,9,10,11]
We determined a probable cause of Onsager-Casimir relations (OCRs) nonreciprocity in three types of quantum Hall devices
Summary
It is widely known that graphene exhibits a variety of unique properties [1,2,3,4]. In certain forms, including epitaxial graphene (EG) grown on 4H-SiC, this versatile material has been identified as a practical way to develop resistance standards based on a robust quantum Hall effect (QHE) that appears over a useable range of magnetic fields (B fields), with the key feature being a well-quantized and extended resistance plateau [5,6,7,8,9,10,11]. Hall bars in parallel or in series to create resistance values of qRK, where q is a positive rational number [13,14,15,16,17,18,19] Before these forms of standard devices are globally implemented, it is critical to disseminate best practices for characterization of the Hall resistance quantization for B field and current dependence. We investigate the root cause of observed nonreciprocity in three types of large graphene quantum Hall devices: standard Hall bars with a length and width of 2 mm and 400 μm, respectively, arrays of 13 parallel elements with quantized resistance RK/26 ≈ 992.8 at the ν = 2 plateau, and a 6.45 k array consisting of eight elements in a seriesparallel configuration.
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
