QSE Junior Quantum Seminar - Yefei Yin

Please join us for the Junior Quantum Seminar with Yefei Yin 尹叶飞 from the Physikalisch-Technische Bundesanstalt (PTB) who will give the talk "The next generation of quantum Hall resistance standards based on n- and p-type epitaxial graphene " on Tuesday May 20th from 9h30-11h.

PLEASE NOTE: The Junior Quantum Series are for gathering  the junior quantum community of master's students, PhDs and post-docs at EPFL, to create a non-judgmental space were scientific ideas can be shared between peers. This event is not for Professors or senior researchers. 

ABTRACT: Historically, the resistance standards were made by physical artifact wire coils before 1990 and quantum resistors based on GaAs heterostructures after 1990. Conventional quantum Hall resistance (QHR) standards based on GaAs heterostructures with the quantized resistance value of R_H = h/2e² (filling factor ν = 2) are operating under the extreme conditions of high magnetic flux density B > 10 T, limited current I < 50 µA, and low temperature T < 1.5 K. These extreme operating conditions significantly hinder the dissemination of primary resistance standards, let alone the commercialization of quantum resistance standards.
In this work, we developed practical primary QHR standards based on n- and p-type epitaxial graphene operating under relaxed conditions. [1-3] Our graphene QHR standards are utilized in the national metrology institutes in Europe countries. The n-type graphene QHR standards achieved a high accuracy of less 2 nΩ/Ω (two parts per billion) at a moderate magnetic flux density of B = 4.5 T, high current of I= 232.5 μA, and easier to access temperature of T = 4.2 K, simultaneously. To our knowledge, this is the best performance of graphene QHR standards achieved in literature so far. The graphene QHR standards have been maintained the 2 nΩ/Ω accuracy in terms of time over 2.5 years, multiple cool-down cycles over fifteen times, and long-distance shipment over 800 km between two metrology institutes. More importantly, our study systematically demonstrated that p-type epitaxial graphene can also be used for primary resistance standards, as accurate (10^-9 accuracy) as GaAs and n-type graphene counterparts for realizing the SI unit ohm in quantum electrical metrology. Furthermore, a contour plot of graphene QHR standards is proposed to reveal the correlation of the quantization regime (10^-9 accuracy) with magnetic field and carrier density. When implemented, graphene QHR standards may lead to a broader dissemination of primary resistance standards beyond national metrology institutes, extending to commercial calibration laboratories and industry on-site.

[1] Y. Yin, et al., Adv. Phys. Res. 1, 2200015 (2022).
[2] Y. Yin, et al., Appl. Phys. Lett., 125, 064001 (2024)
[3] Y. Yin, et al., Phys. Rev. Applied, 23, 014025 (2025)

BIO: Yefei Yin is a postdoctoral researcher at the Physikalisch-Technische Bundesanstalt (PTB), National Metrology Institute in Germany, where he is working on direct current (DC) and alternating current (AC) quantum Hall resistance standards. Previously he completed his PhD at the PTB and Leibniz Universität Hannover, Germany, in 2024, and master’s degree at Fudan University, Shanghai, China, in 2017.