P04: From Resistance Measurement to the Redefinition of the Kilogram: Fascinating World of Topological Phases of Matter (從電阻測量到千克的重新定義：凝聚態物理中奇妙的拓撲物態)

In your high-school physics classes, you’ve probably encountered the Lorentz force and the Hall effect. But did you know that in certain materials, the Hall conductivity isn’t just measurable—it’s quantised with astonishing precision, accurate to nine decimal places? This remarkable phenomenon has reshaped our understanding of matter and even played a key role in redefining the "kilogram"—from a physical object to a value based on fundamental constants. In this talk, we’ll explore the captivating world of topological phases of matter and discover how deep physics connects to everyday measurements.

在高中物理課學習到洛倫茲力和霍爾效應時，你可能已經對這些概念有所了解。但你知道嗎？在某些材料中，霍爾電導不僅可以被測量，甚至能以驚人的精確度被量化——能精確到小數點後九位！這個非凡的現象不僅改變了我們對物質基本狀態的理解，還在重新定義「公斤」這個單位的過程中成為關鍵——從依賴實體標準器轉變為依據基本常數的定義。此演講我將帶大家探索拓撲物質相的奇妙世界，看看深奧的物理如何與日常測量產生聯繫。

Speaker: Prof. Xiao LI
Target Audience: Form 4 - 6
Duration: 45 minutes
Medium of Language: English or Mandarin

Registration: https://www.cityu.edu.hk/csci/local-school-outreach/popular-science-talks