Principal Investigator

Representative works

1.Development of a High-Performance, General-Purpose Magneto-Infrared Spectroscopy System

We have carried out sustained development of magneto-infrared spectroscopy instrumentation, realizing a general-purpose system compatible with both superconducting and resistive magnets. Building upon this platform: (i) an external detection configuration was proposed, achieving full infrared spectral coverage from 1-200 μm under high magnetic fields; (ii) an imaging-based magneto-infrared architecture was developed, significantly improving the signal-to-noise ratio; (iii) an in-situ polarization scheme was established, enabling polarization-resolved magneto-infrared spectroscopy. The system currently operates with simultaneous capabilities of 0-12 T magnetic field, 2-300 K temperature, 1-200 μm wavelength range, a signal-to-noise ratio of 2×10⁴, spectral resolution of 0.02 meV, and in-situ linear/circular polarization resolution, and has been providing long-term open access to users across disciplines worldwide.

…, Xiang Yuan*, A high-flux and high-efficiency setup for magneto-infrared spectroscopy. Review of Scientific Instruments, 96 (11): 113902. (2025)

…, Xiang Yuan*,In-situ polarimetry in collimated magneto-infrared spectroscopy system. Advanced Science Instruments, 1(1), 100005. (2026)

2.Magnetic-Field-Induced Topological States in New Dimensions

     In theory, Weyl fermions can exist in all odd spatial dimensions, yet experimental realizations had been limited to three dimensions. Using magneto-infrared spectroscopy under strong magnetic fields, we identified in HfTe5 a field-induced phase transition from a three-dimensional topological insulator to a one-dimensional Weyl semimetal, dominated by orbital ordering. This led to the observation of one-dimensional Weyl fermions and provided experimental verification of the one-dimensional relativistic optical conductivity formula. In EuCd2As2, we further discovered a magnetic-field-induced three-dimensional van Hove singularity governed by spin ordering, challenging the conventional view that such singularities exist only in two dimensions.

…, Xiang Yuan*, Topological Lifshitz transition and one-dimensional Weyl mode in HfTe5. Nature Materials, 22, 84-91. (2023)

…, Xiang Yuan*, The discovery of three-dimensional Van Hove singularity. Nature Communications, 15, 2313. (2024)

3.Novel Infrared Device Principles under Magnetic Fields

    Circular dichroism reflects structural or electronic chirality in materials. In bulk MnBi₂Te₄, using magneto-infrared spectroscopy under strong magnetic fields, we experimentally induced and observed giant, broadband circular dichroism arising from particle-hole symmetry breaking. This work establishes a new scheme for optical chiral discrimination and introduces a route for controlling topological materials via particle-hole symmetry engineering.

…, Xiang Yuan*, Giant and broadband circular dichroism from particle-hole symmetry breaking in Weyl semimetal. Nature Materials, in press. (2026)

Other Interdisciplinary Studies, Facility Service, and Early Representative Works

…, Xiang Yuan*, Giant superlinear power dependence of photocurrent based on layered Ta2NiS5 photodetector. Advanced Science, 10, 2300413. (2023)

…, Xiang Yuan*, Transmission infrared micro-spectroscopic study of individual human hair, Journal of Biomedical Optics, 28(11), 116501. (2023)

…, Xiang Yuan*, … Memristive switching in the surface of a charge–density–wave topological semimetal. Science Bulletin, 69(13), 2042-2049. (2024)

…, Xiang Yuan*, … Observation of quantum oscillations near the Mott-Ioffe-Regel limit in CaAs3. National Science Review, 11(12) nwae127. (2024)

…, Xiang Yuan#, … Quantum Hall effect based on Weyl orbits in Cd3As2. Nature, 565(7739), 331–336. (2019)

…, Xiang Yuan#, … Ultrahigh conductivity in Weyl semimetal NbAs nanobelts. Nature Materials, 18(5), 482–488. (2019)

Xiang Yuan, … Chiral Landau levels in Weyl semimetal NbAs with multiple topological carriers. Nature Communications, 9(1), 1854. (2018)

Xiang Yuan, … The discovery of dynamic chiral anomaly in a Weyl semimetal NbAs. Nature Communications, 11(1), 1259. (2020)

Undergraduate teaching

He consistently teaches three undergraduate courses: "Solid State Physics", "Low-Dimensional Physics", and "Introduction to Quantum Science". He leads both a Ministry of Education Teaching Reform Project and a Teaching Research Project. Additionally, he is recognized for his contributions to education, with his courses selected as a Shanghai Key Course.