Kuan Hsiang Hsu

All Publications

• A formal FeIII/V redox couple in an intercalation electrode. Nature materials Ramachandran, H., Mu, E. W., Lomeli, E. G., Braun, A., Goto, M., Hsu, K. H., Liu, J., Jiang, Z., Lim, K., Busse, G. M., Moritz, B., Kas, J. J., Vinson, J., Rehr, J. J., Park, J., Abate, I. I., Shimakawa, Y., Solomon, E. I., Yang, W., Gent, W. E., Devereaux, T. P., Chueh, W. C. 2025

  Abstract

  Iron redox cycling between low-valent oxidation states of FeII and FeIII drives crucial processes in nature. The FeII/III redox couple charge compensates the cycling of lithium iron phosphate, a positive electrode (cathode) for lithium-ion batteries. High-valent iron redox couples, involving formal oxidation higher than FeIII, could deliver higher electrochemical potentials and energy densities. However, because of the instability of high-valent Fe electrodes, they have proven difficult to probe and exploit in intercalation systems. Here we report and characterize a formal FeIII/V redox couple by revisiting the charge compensation mechanism of (de)lithiation in Li4FeSbO6. Valence-sensitive experimental and computational core-level spectroscopy reveal a direct transition from FeIII (3d5) to a negative-charge-transfer FeV (3d5L2) ground state on delithiation, without forming FeIV, or oxygen dimers. We identify that the cation ordering in Li4FeSbO6 drives a templated phase transition to stabilize the unique FeV species and demonstrate that disrupting cation ordering suppresses the FeIII/V redox couple. Exhibiting resistance to calendar aging, high operating potential and low voltage hysteresis, the FeIII/V redox couple in Li4FeSbO6 provides a framework for developing sustainable, Fe-based intercalation cathodes for high-voltage applications.

  View details for DOI 10.1038/s41563-025-02356-x

  View details for PubMedID 41094071

  View details for PubMedCentralID 4002152

• Detection of chiral spin fluctuations driven by frustration in Mott insulators Phys. Rev. B Hsu, K. H., Jia, C., Zhang, E. Z., Jost, D., Moritz, B., Hackl, R., Devereaux, T. P. 2025; 111 (20)

  View details for DOI 10.1103/PhysRevB.111.205115

• From Stoner to local moment magnetism in atomically thin Cr2Te3. Nature communications Zhong, Y., Peng, C., Huang, H., Guan, D., Hwang, J., Hsu, K. H., Hu, Y., Jia, C., Moritz, B., Lu, D., Lee, J. S., Jia, J. F., Devereaux, T. P., Mo, S. K., Shen, Z. X. 2023; 14 (1): 5340

  Abstract

  The field of two-dimensional (2D) ferromagnetism has been proliferating over the past few years, with ongoing interests in basic science and potential applications in spintronic technology. However, a high-resolution spectroscopic study of the 2D ferromagnet is still lacking due to the small size and air sensitivity of the exfoliated nanoflakes. Here, we report a thickness-dependent ferromagnetism in epitaxially grown Cr2Te3 thin films and investigate the evolution of the underlying electronic structure by synergistic angle-resolved photoemission spectroscopy, scanning tunneling microscopy, x-ray absorption spectroscopy, and first-principle calculations. A conspicuous ferromagnetic transition from Stoner to Heisenberg-type is directly observed in the atomically thin limit, indicating that dimensionality is a powerful tuning knob to manipulate the novel properties of 2D magnetism. Monolayer Cr2Te3 retains robust ferromagnetism, but with a suppressed Curie temperature, due to the drastic drop in the density of states near the Fermi level. Our results establish atomically thin Cr2Te3 as an excellent platform to explore the dual nature of localized and itinerant ferromagnetism in 2D magnets.

  View details for DOI 10.1038/s41467-023-40997-1

  View details for PubMedID 37660171

  View details for PubMedCentralID PMC10475109

• On the Nature of Valence Charge and Spin Excitations via Multi-Orbital Hubbard Models for Infinite-Layer Nickelates FRONTIERS IN PHYSICS Been, E. M., Hsu, K. H., Hu, Y., Moritz, B., Cui, Y., Jia, C., Devereaux, T. P. 2022; 10

  View details for DOI 10.3389/fphy.2022.836959

  View details for Web of Science ID 000776236900001

• Coulombically-stabilized oxygen hole polarons enable fully reversible oxygen redox ENERGY & ENVIRONMENTAL SCIENCE Abate, I. I., Pemmaraju, C., Kim, S., Hsu, K. H., Sainio, S., Moritz, B., Vinson, J., Toney, M. F., Yang, W., Gent, W. E., Devereaux, T. P., Nazar, L. F., Chueh, W. C. 2021

  View details for DOI 10.1039/d1ee01037a

  View details for Web of Science ID 000671934700001