Interviews with Faculty Researchers

– Interview with Prof. Loh Kian-ping
Chair Professor of Materials Physics and Chemistry (Global STEM Professorship Scheme), Department of Applied Physics

In the third century BCE, a single building – the Great Library of Alexandria—was believed to house the sum of human knowledge. Today, however, information is measured not in books – nor even in the floppy disks or computer hard drives of last century’s technology – but in trillions of gigabytes of digital data. To turn this flood of information into knowledge, it must be properly stored, processed and analysed. However, computational power may not be keeping pace with the rise of big data. Currently, the exponentially increasing volume of digital information demands a huge amount of electrical energy for switching circuit components during computation, which is creating a bottleneck in big data storage and analytics.

The answer may lie in a state-of-the-art emerging technology known as spintronics, according to Prof. Loh Kian-ping, Chair Professor of Materials Physics and Chemistry of the Department of Applied Physics. “Spintronics is an area targeted by researchers to develop next-generation devices to reduce power consumption and to increase their memory and processing capabilities,” notes Prof. Loh. Also known as “spin electronics”, spintronics is the use of a fundamental property of electrons, known as “spin”, for information processing. Whereas traditional electronic devices use the electrical charge of electrons to encode data, spintronic devices instead exploit the spin of electrons and use their intrinsic angular momentum.

Devices based on spin current have the potential to be significantly faster and more energy-efficient than conventional electronic systems, massively reducing cost and increasing storage density and computational power. Spintronics offers huge potential in the development of nanoscale devices for mass data storage, as spintronic devices can compress as many as one trillion bits of data within a single square inch. Current applications include information storage in the read/ write heads of computers’ magnetic hard disk drives.

Prof. Loh is at the cutting edge of research in this important field, as his work focuses on spintronics in two-dimensional materials, such as Weyl semimetals and topological insulators. The unusual physical properties of such materials make them an exciting new platform for exploring spintronic devices both theoretically and experimentally. “We study how the special structures of two-dimensional materials enable charge to be converted into spin, and vice versa, efficiently,” Prof. Loh explains. Ultimately, this research may represent a breakthrough in meeting the demand for ever lower-power, higher-performance storage and processing in the era of big data.

二維材料的自旋電子學

– 羅健平教授專訪
應用物理學系材料物理及化學講座教授
「傑出創科學人計劃」

在公元前三世紀，人們認為單憑亞歷山大圖書館，便足以容納所有人類知識。到了今天，資訊不再以書籍來衡量，甚至也不再以上世紀技術的磁碟或電腦硬碟來衡量，而是以數萬億千兆位元組的數碼資料來計算。要把滔滔不絕的資訊轉化為知識，便必須進行適當的儲存、處理和分析。然而，電腦的計算能力可能無法緊貼大數據興起的需要。目前，數碼資訊量幾何級增加，在計算過程中切換電路元件耗電龐大，造成了大數據儲存和分析的瓶頸。根據應用物理學系材料物理及化學講座教授羅健平教授所說，最先進的新興技術「自旋電子學」可能是解決這難題的答案。他提出：「自旋電子學的研究人員努力研發下一代設備，務求降低功耗並提高記憶體和處理能力。」自旋電子學利用電子「自旋」的基本性質來處理資訊。傳統的電子設備使用電子的電荷來為數據編碼，但自旋電子設備則利用電子的內稟角動量。

以自旋電流為基礎的設備有潛力運作得比傳統電子系統更快和更節省能源，從而大幅降低成本，同時提高儲存密度和計算能力。由於自旋電子設備可以把多達1萬億位元的數據壓縮到1平方英吋內，所以自旋電子學具有巨大潛力，能有助開發納米級設備所需要的大容量數據儲存。在電腦磁碟驅動器的讀／寫磁頭中儲存資訊，便是其中一種現有應用。

羅教授是這重要研究領域的先鋒，他專注研究二維材料中的自旋電子學，例如外爾半金屬和拓撲絕緣體。這些材料不尋常的物理性質，為自旋電子設備建立了令人雀躍的理論與實驗探索新平台。羅教授解釋說：「我們研究二維材料的特殊結構如何有效地使電荷轉化為自旋，又或使自旋轉化為電荷。在大數據時代中，這項研究最終可能會滿足更低功耗、更高儲存和處理性能的需求，成為重大突破。」