IQIM Postdoctoral and Graduate Student Seminar

Monday, July 28, 2025

2:00pm to 3:00pm

East Bridge 114

Observing the electronic response of a Mott insulator at a current-induced insulator-to-metal transition using transport-ARPES

Cissy Suen, Max Plank Institute & University of British Columbia,

Note special date and time for this talk - Monday, July 28 beginning at 2 pm

Abstract: The quasi-two-dimensional Mott insulator Ca2RuO4 exhibits a convergence of spin-orbit coupling and electronic correlations that lead to exciting quantum phenomena [1], including a rare insulator-to-metal transition (IMT) induced by a DC current [2]. While structural changes have been tracked by neutron diffraction [3], Raman scattering [4], and x-ray diffraction [5], the associated electronic changes had not been observed. Here we report angle-resolved photoemission spectroscopy (ARPES) results under DC current, which show a substantial reduction of the Mott gap, along with a change in the Ru t2g band dispersion [6]. We have also captured the high temperature Fermi surface, whose spectral features are unique from the current-induced metallic Fermi surface. In conjunction with a free energy analysis, our results demonstrate that the current-induced phase, albeit thermodynamically equivalent, is electronically distinct from the high-temperature zero-current metallic phase.

Combining ARPES with transport, i.e. transport-ARPES, has been rare given the complexity of disassociating real field- or current-driven physics from the effect of stray electric and magnetic fields on the outgoing photoelectron trajectory. By taking advantage of the micron-sized beam spot at the MAESTRO beamline (7.0.2) at the Advanced Light Source and careful core level spectrum analysis, we show that transport-ARPES can be extended to the study of any ARPES-suitable material. I will include an overview on transport-ARPES, as well as a brief outlook on the exciting prospects of in operando spectroscopy.

[1] A. Jain et al., Nat. Phys. 13 (2017) 633-637

[2] R. Okazaki et al., J. Phys. Soc. Jpn 82 (2013) 103702

[3] J. Bertinshaw et al., Phys. Rev. Lett 123 (2019) 137204

[4] K. Fürsich et al., Phys. Rev. B 100 (2019) 081101

[5] K. Jenni et al., Phys. Rev. Mat 4 (2020) 085001

[6] C.T. Suen et al., Nat. Phys. 20 (2024) 1757–1763

For more information, please contact Marcia Brown by phone at 626-395-4013 or by email at [email protected].

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IQIM Postdoctoral and Graduate Student Seminar Series

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