Condensed Matter Physics in the Alps: Geometric Frustration, Topology, Flat Bands, and Correlation in Kagome and Van der Waals Systems

Session

Wednesday Afternoon Session, Chair L. Yang

Jan 7, 2026, 5:00 PM

Saas Fee

31. Soft-phonon CDW formation in Kagome metals

Yu SONG (Zhejiang University)

1/7/26, 5:00 PM

Kagome experimental

Contributed talk

Kagome metals host van Hove points and flat bands, with the resulting nesting effects potentially leading to unconventional CDW states. Using inelastic X-ray scattering, we show that the CDW in KV3Sb5 forms via a continuous softening of phonons to zero energy, similar to transition metal dichalcogenides (such as NbSe2). The soft phonons exhibit a prominent in-plane anisotropy that mirrors the...

34. Altermagnetism and Flat band Enhanced AFM Fluctuation in Kagome CsCr3Sb5

Chenchao Xu (Hangzhou Normal University)

1/7/26, 5:20 PM

Theory

Contributed talk

The CsCr3Sb5 exhibits superconductivity in close proximity to a density-wave (DW) like ground state at ambient pressure, however details of the DW are still elusive. Using first-principles density-functional calculations, we found its ground state to be a 4×2 altermagnetic spin-density-wave (SDW) at ambient pressure. The magnetic long range order is coupled to the lattice, generating 4a0...

21. Unusual aspects of the coherent phonon in CsV3Sb5: its implication for the loop-current and chirality

Chennan Wang (Universität Freiburg)

1/7/26, 5:40 PM

Kagome experimental

Contributed talk

The question of time-reversal symmetry breaking in CsV3Sb5 remains an open and debated topic, with no definitive consensus established to date. Conventional magnetic field-sensitive probes have not conclusively confirmed the presence of time-reversal symmetry-breaking fields. This presentation will provide new insights into this crucial aspect through a study into the optical coherent phonon...

58. Real-time twisting on a chip

Yuan Cao (UC Berkeley)

1/7/26, 6:00 PM

van der Waals experimental

Invited talk (by invitation only)

Two-dimensional materials (2DM) and their heterostructures offer tunable electrical and optical properties, primarily modifiable through electrostatic gating and twisting. While electrostatic gating is a well-established method for manipulating 2DM, achieving real-time control over interfacial properties remains a frontier in exploring 2DM physics and advanced quantum device technology....