Michael Buchhold co-authors a Nature Physics paper on a Hubbard exciton fluid in Mott insulators


A Hubbard exciton fluid in a photo-doped antiferromagnetic Mott insulator is the title of a paper arising from a cooperation between ML4Q member, Michael Buchhold (Institute for Theoretical Physics, Cologne) and the group of David Hsieh at CalTech. Also part of the study is Zala Lenarcic, former postdoc in the Rosch Group, meanwhile research group leader at the Jozef Stefan Institute in Ljubliana.

The paper reports a transient formation of a Hubbard exciton fluid in the antiferromagnetic Mott insulator Sr2IrO4 using ultrafast terahertz conductivity Michael and Zala contributed the theoretical analysis. Following photo-excitation, the authors observe rapid spectral-weight transfer from a Drude metallic response to an insulating response. The latter is characterized by a finite-energy peak originating from intraexcitonic transitions, whose assignment is corroborated by numerical simulations of an extended Hubbard model.

The focus of the Hsieh Resarch Group is to search for novel quantum electronic phases of matter in solids and to understand and control their properties. To study these questions, they are developing a variety of laser-based techniques including nonlinear optical spectroscopy and microscopy, angle-resolved photoemission spectroscopy and time-resolved optical spectroscopy.

Zala Lenarcic moved to Ljubliana three years ago after a postdoc experience in the the Rosch Research Group in Cologne. There, she started her own research group focusing on nonequilibrium dynamics.

PD Michael Buchhold is leading his junior research group working on quantum dynamics out of equilibrium at the Institute for Theoretical Physics in Cologne since January 2023. From 2020 until the end of 2022 he was a senior postdoc in the group of Sebastian Diehl. Michael did his PhD at TU Dressden and was a Feodor Lynen Fellow at the California Institute of Technology before coming to Cologne.

Publication: Mehio, O., Li, X., Ning, H. et al. A Hubbard exciton fluid in a photo-doped antiferromagnetic Mott insulator. Nat. Phys. (2023). https://doi.org/10.1038/s41567-023-02204-2

Theoretical simulations showing the Eigenstates of HtJV in the sector of a single HD pair at zero centre-of-mass momentum calculated via exact diagonalization. From: A Hubbard exciton fluid in a photo-doped antiferromagnetic Mott insulator



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