崔琦講座第9講

報告題目： A New International System of Units in 2018!? How my Nobel Prize Contributed to this Development 演講人： Professor Klaus von Klitzing, 馬普固态研究所, 1985年諾貝爾物理學獎獲得者時間： 2015年05月08日 10:00 地點：中科院物理所M樓234報告廳報告人簡介： Klaus von Klitzing教授，德國物理學家，1943年生。他在1980年研究二維電子氣在強磁場中的輸運性質時發現了量子霍爾效應，并因此獲得1985年諾貝爾物理學獎。國際計量标準化組織在1990年決定使用量子霍爾電阻作為電阻的國際标準，并用他的名字命名（克裡青常數）。這一發現的重要性還在于量子霍爾電阻的精确性與普适性引發了規範不變性、幾何相位和拓撲不變量等重要理論概念在許多體系中的應用，相關研究對近年來拓撲絕緣體和拓撲半金屬等新物态的發現起到了促進作用。von Klitzing教授在1972年獲得德國烏茲堡大學博士學位，1980-1985年任慕尼黑工大教授，從1985年起一直在位于斯圖加特的馬普固态研究所擔任研究主任，主要從事低維電子體系方面的研究。 Abstract： The International System of Units (SI units) forms the basis for all measurements. With the Meter Convention in 1875 a worldwide system of units was introduced with prototypes for the meter and kilogram kept at the Bureau International des Poids et Mesures in Sevres. Even today the kilogram prototype is by definition the unit of mass whereas the unit of length has been replaced in 1983 by a fixed value for the velocity of light (in combination with the well-known time unit from atomic clocks).
Long-term comparisons of the kilogram prototype with other mass standards indicate, that the prototype is not stable with time so that the General Conference on Weights and Measures at his last meeting in November 2014 published a resolution with the recommendation to define the SI units in terms of invariants of nature; the new definitions will be based on fixed numerical values of the Planck constant (h), the elementary charge (e), the Boltzmann constant (k), and the Avogadro constant (NA), respectively. A prerequisite for such a change is the precise experimental realization of practical standards on the basis of natural constants.
The quantized Hall resistance (Nobel Prize 1985) plays a crucial role for the implementation of a new SI system since this quantum resistance can be used not only for high precision realizations of electrical standards but also for a new realization of a kilogram by comparing electrical and mechanical forces with the Watt balance.
The talk summarizes the application of the quantum Hall effect in metrology with the focus on the replacement of the kilogram by a fixed value for the Planck constant. 聯系人：李永慶研究員 (010-82649557)