Unraveling the Mystery of Deconfined Quantum Critical Points

A recent study, led by Professor Zi Yang MENG and co-authored by his PhD student Menghan SONG of HKU Department of Physics, in collaboration with researchers from the Chinese University of Hong Kong, Yale University, University of California, Santa Barbara, Ruhr-University Bochum and TU Dresden, has unravelled some of the secrets concealed within the deconfined quantum critical points. Their findings, recently published in the prestigious journal Science Advances, push the boundaries of modern physics and offer a fresh perspective on how quantum matter operates at these enigmatic junctures.

Congratulations, Dr. Lu

On April 16, 2025, Mr. Hongyu Lu marked a pivotal achievement by successfully defending his Ph.D. thesis, entitled "Numerical studies of fractional quantum anomalous Hall states: Emergent forms, collective excitations, and phase transitions". His clear and compelling presentation of his research findings from his time at HKU, along with his confident responses to impromptu questions, earned high praise from the Examining Committee, which included Prof. Xi Dai from HKUST, and Profs. Wang Yao and Dong-Keun Ki from HKU. Congratulations to Dr. Hongyu Lu! We wish him continued success and look forward to his contributions as an emerging leader in theoretical condensed matter physics. Continue reading

从《马说》到《Super-moire 说》

世有 moiré,然后有 super-moiré。Moiré 者常有,而 super-moiré 不常有。
Moiré 之 super 者,其原胞尺度可达百纳米,向之作者不知其能 super 而制也。
是 super-moiré 也,其成于常规 moiré 之量子干涉效应,波粒二象性之力良有以也。
以百纳米之原胞,所含磁通之量亦增百倍,Brown-Zak 振荡正比于磁场之现象,昭然于世也。
噫!Brown-Zak,侯世达诸前辈得见今日之数据,其必曰“微斯人,吾谁与归”矣。Continue reading

Entanglement Microscopy: How Matter Entangles in Quantum Many-Body Systems

A collaboration between Mr. Ting-Tung Wang, Mr. Menghan Song, and Professor Zi Yang Meng from the Department of Physics at The University of Hong Kong (HKU) together with their collaborators Liuke Lyu and William WITCZAK-KREMPA from the University of Montreal has recently developed a novel algorithm in quantum physics known as ‘entanglement microscopy’ that enables visualization and mapping of this extraordinary phenomenon at a microscopic scale. Their study was published in a recent issue of Nature Communications. Using the algorithm, one can uncover the hidden structures of quantum matter, revealing insights that could transform technology and deepen the understanding of the universe. Continue reading

AI and quantum physics (and ancient Greece and mahjong)

In this interview with HKU science editor, Dr Pavel Toropov, Professor Meng explains why AI is now indispensable in quantum physics research ­– by allowing us to circumvent the need for enormous computational complexity, AI can help to make breakthroughs and in the process help us to understand better of mother nature and ourselves. This leads to discoveries of quantum materials whose properties, such as superconductivity and entanglement, can change the world. The technology may be cutting edge, but the principles involved, says Prof Meng, go back to ancient greek maxim - know thyself, and the whole thing is similar to playing mahjong. Click here for the interview.

Thoughts on the 2024 Nobel Prizes: Where will Artificial Intelligence take Science and Scientists?

In 2024, Artificial Intelligence (AI) achieved a remarkable milestone by winning the Nobel Prizes in both Physics and Chemistry. This unprecedented event sparked a significant debate about the role of AI in revolutionizing traditional methods and paradigms in scientific research. In light of these developments, FanPu (返朴) saw it as an opportune moment to initiate a deep discussion on this topic. They invited Prof. Meng to join a live forum with Prof. Pei Wang, the vice chair of the Artificial General Intelligence Society from Temple University, Prof. Yuqing Lou, a well-known astrophysicist from the Department of Physics at Tsinghua University, and Prof. Xu Li, a biochemistry and structural biologist from the University of Science and Technology of China, to share their thoughts on where AI will take science and scientists.

Congratulations to Professor Meng for winning the 2024 Top China Cited Paper Award (Physics)

Our team was one of the winners of the 2024 Top China Cited Paper Award (Physics) for "Momentum Space Quantum Monte Carlo on Twisted Bilayer Graphene", published in Chinese Physics Letters. This award for China-based authors is given to the top ten papers in the top 1% of the most cited articles published in IOP Publishing journals over the past three years (2021 – 2023). This data is from the citations recorded in Web of Science. This article (Chin. Phys. Lett. 38, 077305 (2021)) has developed a momentum space quantum Monte Carlo algorithm to deal with the long-range Coulomb interaction problem that emerges in two-dimensional quantum moire materials such as twisted graphene, which is one of the universal challenges in correlated electron systems. Three years ago, Zi Yang quoted the famous poetry of ancient Chinese poet Jiang Kui(姜夔) to explain how the “Coulomb force is endless, momentum Monte Carlo sends longing thoughts”(库伦作用无尽期,动量蒙卡寄相思) inspire them to pursue the research of long range interaction in quantum moire systems. The quantum many-body paradigm of the moire system is becoming a beautiful stream that carries them to the heartland of scientific creativity.

Dimensionality crossover to a 2D vestigial nematic state from a 3D antiferromagnet in a honeycomb van der Waals magnet

A collaboration between theoretical physicists Dr. Chengkang Zhou and Professor Zi Yang Meng from the Department of Physics at The University of Hong Kong (HKU), along with experimentalists Dr. Zeliang Sun, Professors Kai Sun and Liuyan Zhao from the Department of Physics at the University of Michigan, and Professor Rui He from the Department of Electrical and Computer Engineering at Texas Tech University, has led to a significant discovery in quantum physics. Their study was published in a recent issue of Nature Physics (Nat. Phys. (2024)) with cash financing loansonlineusa, which has been very helpful in advancing the research. The research team was the first to experimentally observe a transition from a 3-dimensional (3D) long-range order state to a 2-dimensional (2D) flat pattern vestigial order state in NiPS3. The vestigial order can be seen as the retention during the process of symmetry breaking. This occurs when the primary magnetic long-range order state breaks down into a simpler form - in this case, a 2D vestigial order state (known as Z3 Potts-nematicity) - as the NiPS3 material is thinned. The collaboration between the large-scale Monte Carlo simulation and the experiments led to this discovery during the dimension crossover process. Continue reading.

Bye, Mr. Zhang

Congratulations from Zi Yang:

August 6, 2024, is a significant day for Mr. Xu Zhang, as on this day he has successfully defended his Ph.D. thesis with the title “Electromagnetic response in two dimensional flat band systems”. He has greatly impressed the Examining Committee comprised of Profs. Xi Dai and Ning Wang from HKUST and Profs. Wang Yao and Dong-Keun Ki from HKU, in clearly presenting the major research outputs during his Phd years in HKU, as well as addressing the interesting questions spontaneously appeared during the defense. Congratulations to Dr. Xu Zhang! And hope him a successful next step and becomes the next rising star in theoretical condensed matter physics. Continue reading

Spectral evidence for Dirac spinons in a kagome lattice antiferromagnet

A collaboration between theoretical physicists Dr. Chengkang ZHOU and Professor Zi Yang MENG from the Department of Physics at The University of Hong Kong (HKU), along with experimentalists Mr. Zhenyuan ZENG and Professor Shiliang LI at the Institute of Physics (IOP), Chinese Academy of Sciences (CAS), and Professor Kenji NAKAJIMA from J-PARC Center, Japan, has led to a discovery in the realm of quantum physics. Their study, published in a recent issue of Nature Physics ( Nat. Phys. 20, 1097–1102 (2024)), sheds light on the long-anticipated emergence of quasiparticles, akin to the famous Dirac particles obeying the relativistic Dirac equation. These quasiparticles, known as Dirac spinons, were theorised to exist within a novel quantum state called a quantum spin liquid state loans-cash.net. This work captures the conic spin excitations arising from Dirac spinons, resulting in low-energy spin excitations with sharp energy-momentum characteristics. Their results provide strong evidence for the emergence of a Dirac quantum spin liquid state in YCu3-Br. Continue reading