In: Physical Review B, 2016, vol. 94, no. 20, p. 201106
The cubic perovskite SrVO3 is generally considered to be a prototype strongly correlated metal with a characteristic three-peak structure of the d-electron spectral function, featuring a renormalized quasiparticle band in between pronounced Hubbard sidebands. Here we show that this interpretation, which has been supported by numerous “ab initio” simulations, has to be reconsidered. Using...
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In: Physical Review B, 2019, vol. 99, no. 23, p. 235133
Nonlocal order parameters in space-time are proposed to characterize the unconventional orbital-selective conducting state in fulleride superconductors, called the Jahn-Teller metal. In previous works, it has been argued that this state can be interpreted as a spontaneous orbital-selective Mott state, in which the electrons in two of the three t1u molecular orbitals are localized, while those...
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In: Physical Review B, 2017, vol. 95, no. 19, p. 195405
We study the controlled manipulation of the Jahn-Teller metal state of fulleride compounds using nonequilibrium dynamical mean-field theory. This anomalous metallic state is a spontaneous orbital-selective Mott phase, which is characterized by one metallic and two insulating orbitals. Using protocols based on transiently reduced hopping amplitudes or periodic electric fields, we demonstrate...
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In: Scientific Reports, 2016, vol. 6, p. 21235
Ultra-fast spectroscopy can reveal the interplay of charges with low energy degrees of freedom, which underlies the rich physics of correlated materials. As a potential glue for superconductivity, spin fluctuations in Mott insulators are of particular interest. A theoretical description of the coupled spin and charge degrees of freedom is challenging, because magnetic order is often only...
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In: Physical Review B, 2020, vol. 101, no. 3, p. 035203
We study the time evolution of excitonic states after photoexcitation in the one- dimensional spinless extended Falicov-Kimball model. Several numerical methods are employed and benchmarked against each other: time-dependent mean-field simulations, the second-Born approximation (2BA) within the Kadanoff-Baym formalism, the generalized Kadanoff-Baym ansatz (GKBA) implemented with the 2BA, and...
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In: Physical Review Letters, 2017, vol. 119, no. 8, p. 086401
We report on the nonequilibrium dynamics of the electronic structure of the layered semiconductor Ta2NiSe5 investigated by time- and angle-resolved photoelectron spectroscopy. We show that below the critical excitation density of FC=0.2 mJ cm−2, the band gap narrows transiently, while it is enhanced above FC. Hartree-Fock calculations reveal that this effect can be explained by the presence...
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In: Physical Review B, 2021, vol. 104, no. 3, p. 035125
Black phosphorus is a quasi-two-dimensional layered semiconductor with a narrow direct band gap of 0.3 eV. A giant surface Stark effect can be produced by the potassium doping of black phosphorus, leading to a semiconductor to semimetal phase transition originating from the creation of a strong surface dipole and associated band bending. By using time- and angle-resolved photoemission ...
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In: Physical Review Letters, 2018, vol. 120, no. 16, p. 166401
Strongly correlated materials exhibit intriguing properties caused by intertwined microscopic interactions that are hard to disentangle in equilibrium. Employing nonequilibrium time-resolved photoemission spectroscopy on the quasi-two- dimensional transition-metal dichalcogenide 1T-TaS2, we identify a spectroscopic signature of doubly occupied sites (doublons) that reflects fundamental Mott...
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In: Nature Communications, 2020, vol. 11, no. 1, p. 4095
Charge excitations across an electronic band gap play an important role in opto- electronics and light harvesting. In contrast to conventional semiconductors, studies of above-band-gap photoexcitations in strongly correlated materials are still in their infancy. Here we reveal the ultrafast dynamics controlled by Hund’s physics in strongly correlated photoexcited NiO. By combining...
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In: Physical Review B, 2018, vol. 97, no. 24, p. 245129
The nonequilibrium Green's functions (NEGF) approach is a versatile theoretical tool, which allows to describe the electronic structure, spectroscopy, and dynamics of strongly correlated systems. The applicability of this method is, however, limited by its considerable computational cost. Due to the treatment of the full two-time dependence of the NEGF, the underlying equations of motion...
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