Our research has focused on the discovery, synthesis, and study of novel quantum materials [1]. In this seminar, I report two of our most recent discoveries: (1) A chiral-orbital-currents state that underpins a novel colossal magnetoresistance without a net magnetic polarization and a strongly current-sensitive Hall effect with a large Hall angle reaching up to 0.15 (comparable to the highest values yet reported) in ferrimagnetic Mn3Si2Te6 [2-4], and (2) A heavy Fermi surface of charge-neutral spinons that supports both a heavy-fermion-strange-metal and adjacent quantum- spin-liquid phases in the 4d-electron trimer lattice Ba4Nb1-xRu3+xO12 (without f electrons). The extraordinarily large entropy and linear electronic heat capacity of both phases extend into milli- Kelvin temperatures, which is best explained by charge and spin dissociation. The insulating spin liquid is a much better thermal conductor than the heavy-fermion-strange-metal that is separately observed to strongly violate the Wiedemann-Franz law [5].
References
1. Physics of Spin-Orbit-Coupled Oxides, Gang Cao and Lance E. De Long, Oxford University Press; Oxford, 2021.
2. Control of chiral orbital currents in a colossal magnetoresistance material, Yu Zhang, Yifei Ni, Hengdi Zhao, Sami Hakani, Feng Ye, Lance DeLong, Itamar Kimchi, and Gang Cao, Nature 611, 467–472 (2022).
3. Colossal magnetoresistance via avoiding fully polarized magnetization in ferrimagnetic insulator Mn3Si2Te6, Yifei Ni, Hengdi Zhao, Yu Zhang, Bing Hu, Itamar Kimchi and Gang Cao, Letter of Phys. Rev. B 103, L161105 (2021).
4. Current-sensitive Hall effect in a chiral-orbital-current state, Yu Zhang, Yifei Ni, Pedro Schlottmann, Rahul Nandkishore, Lance E. DeLong, and Gang Cao, submitted, 2023. 5. Transition between heavy-fermion-strange-metal and spin liquid in a 4d-electron trimer lattice, Hengdi Zhao, Yu Zhang, Pedro Schlottmann, Rahul Nandkishore and Gang Cao, submitted, 2023 https://doi.org/10.48550/arXiv.2305.01033