Emmanouil Frantzeskakis I “V2O3 : A direct view of changes in its electronic structure across the metal-to-insulator transition”

Emmanouil Frantzeskakis (ISMO), Université Paris Saclay

In V2O3, the formal configuration of the vanadium ions is V+3[3d2]. Thus, as its conduction

band is partially filled, according to band theory, this oxide should be a metal. However, V2O3
shows a first-order metal-to-insulator transition (MIT) when cooling below T ~ 160 K, with an
abrupt resistivity change of 7 orders of magnitude, accompanied by a corundum-tomonoclinic
structural transition and a paramagnetic to antiferromagnetic transition. In fact,
the partially filled d-bands of V2O3 are prone to strong electron interactions, neglected in band
theory. Hence, V2O3 is considered an archetype of the Mott MIT, one of the most fundamental
phenomena of electron correlations. However, after 50 years of research, the microscopic
mechanism behind the Mott MIT is still controversial [1-4].
In this talk, I will review our recent experimental results on V2O3 thin films by means of Angle
Resolved PhotoEmission Spectroscopy (ARPES). I will argue that we have for the first time
succeeded to measure the electronic structure changes of V2O3 across the MIT. The clear
spectroscopic fingerprints give new important insight to the underlying mechanism of this
paradigmatic Mott transition [5].
Time permitting, I will present further ARPES results on another hotly debated quantum
system: the heavy-fermion compound URu2Si2. Its transition below 17 K into a quantum phase
with an unknown order parameter has sparked the interest of the condensed matter
community in the last 40 years [6-8]. We aim to shed new light into this so-called hidden order
phase by comparing the corresponding experimental electronic structure with the electronic
structure of the same compound in well-known quantum phases [9].

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[3] M. J. Rozenberg et al., Phys. Rev. Lett. 75, 105 (1995).
[4] A. I. Poteryaev et al., Phys. Rev. B 76, 085127 (2007).
[5] M. Thees et al., Science Advances 7, eabj 1161 (2021).
[6] M. B. Maple et al., Phys. Rev. Lett. 56, 185 (1986).
[7] T. T. M. Palstra et al., Phys. Rev. Lett. 55, 2727 (1985).
[8] J. A. Mydosh et al., Rev. Mod. Phys. 83, 1301 (2011).
[9] E. Frantzeskakis et al., PNAS 118, e2020750118 (2021).