# Event Details

- **Event Name**: Seminar by Dr. Fazhi YANG (CityU)
- **Event Start and End Date**: Wed, 06 Aug, 2025 at 02:00 pm – Wed, 06 Aug, 2025 at 03:00 pm
- **Event Description**: In one-dimensional quantum materials, conducting electrons and the underlying lattices can undergo a spontaneous translational symmetry breaking, known as Peierls transition [1]. For nearly a century, the Peierls transition has been understood within the paradigm of electron-electron interactions mediated by longitudinal acoustic phonons. This classical picture has recently been revised in topological semimetals, where transverse acoustic phonons can couple with conducting p-orbital electrons and give rise to an unconventional Fermi surface instability, dubbed the transverse Peierls transition (TPT) [2]. Most interestingly, the TPT induced lattice distortions can further break rotation or mirror/inversion symmetries, leading to nematic or chiral charge density waves (CDWs). In this talk, I will present experimental observation of an incommensurate TPT in tetragonal Dirac semimetal EuAl4 [3]. We observed the complete softening of a transverse acoustic phonon at the CDW wave vector upon cooling, whereas the longitudinal acoustic phonon is nearly unchanged. The first-principles calculations show that the incommensurate CDW wave vector matches the calculated charge susceptibility peak and connects the nested Dirac bands with Al 3px and 3py orbitals. Our second harmonic generation measurements show that the CDW induced lattice distortions break all vertical and diagonal mirrors whereas the four-fold rotational symmetry is retained below the CDW transition. These observations strongly suggest a chiral CDW in EuAl4 and highlight the TPT as a new avenue for chiral quantum states.

[1] Frohlich, H. On the Theory of Superconductivity: The One-dimensional Case, Proc. of the Royal Soc. A 233, 296 (1954).
[2] Luo, K. F. & Dai, X. Transverse Peierls Transition, Phys. Rev. X 13, 011027 (2023).
[3] Yang, F. Z. et al., Incommensurate Transverse Peierls Transition, arXiv: 2410.10539 (2024).
- **Event URL**: https://allevents.in/hong-kong/seminar-by-dr-fazhi-yang-cityu/200028596607211
- **Event Categories**: workshops, music, entertainment
- **Interested Audience**: 
  - total_interested_count: 1

## Ticket Details


## Event venue details

- **city**: Hong Kong
- **state**: HK
- **country**: Hong Kong
- **location**: Rm G26, Science Centre North Block, The Chinese University of Hong Kong
- **lat**: 22.29912
- **long**: 114.17223
- **full address**: Rm G26, Science Centre North Block, The Chinese University of Hong Kong, 90 Nathan Rd, Tsim Sha Tsui, Kowloon, Hong Kong SAR, Hong Kong, Hong Kong

## Event gallery

- **Alt text**: Seminar by Dr. Fazhi YANG (CityU)
  - **Image URL**: https://cdn-az.allevents.in/events4/banners/63be1a0dafb09f27a5f1b77a58724588c07be6f48c3402c5cd13ca4bbb944096-rimg-w1200-h1708-dcffffff-gmir?v=1753973342

## FAQs

- **Q**: When and where is Seminar by Dr. Fazhi YANG (CityU) being held?
  - **A:** Seminar by Dr. Fazhi YANG (CityU) takes place on Wed, 06 Aug, 2025 at 02:00 pm to Wed, 06 Aug, 2025 at 03:00 pm at Rm G26, Science Centre North Block, The Chinese University of Hong Kong, 90 Nathan Rd, Tsim Sha Tsui, Kowloon, Hong Kong SAR, Hong Kong, Hong Kong.
- **Q**: Who is organizing Seminar by Dr. Fazhi YANG (CityU)?
  - **A:** Seminar by Dr. Fazhi YANG (CityU) is organized by Department of Physics, CUHK 香港中文大學物理系.
- **Q**: Who is this event for? Is it right for me?
  - **A:** Seminar by Dr. Fazhi YANG (CityU) is ideal for curious learners, students, and skill-builders looking to gain hands-on knowledge and practical expertise in a focused, interactive setting. Whether you're a first-time attendee or a longtime enthusiast in Hong Kong, this event is thoughtfully curated to deliver a standout experience worth every moment. If Seminar by Dr. Fazhi YANG (CityU) sounds like your kind of event, don't wait - spots fill up fast.

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