Exciton Mott transition revisited

Guerci, Daniele; Capone, Massimo; Fabrizio, Michele

doi:10.1103/physrevmaterials.3.054605

Cited by 40 publications

(45 citation statements)

References 67 publications

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“…The latter remain finite at zero temperature, the effective exchange is therefore well-defined in this limit. The calculation of the spin susceptibility in the Mott phase at zero temperature is an unsolved problem [1,48,49].…”

Section: Discussionmentioning

confidence: 99%

Efficient evaluation of the polarization function in dynamical mean-field theory

Krien

2019

Phys. Rev. B

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The dynamical susceptibility of strongly correlated electronic systems can be calculated within the framework of the dynamical mean-field theory (DMFT). The required measurement of the four-point vertex of the auxiliary impurity model is however costly and restricted to a finite grid of Matsubara frequencies, leading to a cutoff error. It is shown that the propagation of this error to the lattice response function can be minimized by virtue of an exact decomposition of the DMFT polarization function into local and nonlocal parts. The former is measured directly by the impurity solver, while the latter is given in terms of a ladder equation for the Hedin vertex that features an unprecedentedly fast decay of frequency summations compared to previous calculation schemes, such as the one of the dual boson approach. At strong coupling the local approximation of the TRILEX approach is viable, but vertex corrections to the polarization should be dropped on equal footing to recover the correct prefactor of the effective exchange. In finite dimensions the DMFT susceptibility exhibits spurious mean-field criticality, therefore, a two-particle self-consistent and frequency-dependent correction term is introduced, similar to the Moriya-λ correction of the dynamical vertex approximation. Applications to the two-and three-dimensional Hubbard models on the square and cubic lattices show that the expected critical behavior near an antiferromagnetic instability is recovered. arXiv:1901.02832v2 [cond-mat.str-el]

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Section: Discussionmentioning

confidence: 99%

Efficient evaluation of the polarization function in dynamical mean-field theory

Krien

2019

Phys. Rev. B

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“…We rationalize these observations through a model based on the semiconductor Bloch equations (SBEs), which confirms the absence of a sharp insulatorto-metal transition in the system and witnesses a crossover between the two phases. These results highlight the crucial role of e-h correlations in a regime where complete exciton dissociation is otherwise expected, paving the way towards a deeper understanding of the many-body phenomena emerging in semiconductors upon intense illumination 47 .…”

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confidence: 79%

Mahan excitons in room-temperature methylammonium lead bromide perovskites

et al. 2020

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In a seminal paper, Mahan predicted that excitonic bound states can still exist in a semiconductor at electron-hole densities above the insulator-to-metal Mott transition. However, no clear evidence for this exotic quasiparticle, dubbed Mahan exciton, exists to date at room temperature. In this work, we combine ultrafast broadband optical spectroscopy and advanced many-body calculations to reveal that organic-inorganic lead-bromide perovskites host Mahan excitons at room temperature. Persistence of the Wannier exciton peak and the enhancement of the above-bandgap absorption are observed at all achievable photoexcitation densities, well above the Mott density. This is supported by the solution of the semiconductor Bloch equations, which confirms that no sharp transition between the insulating and conductive phase occurs. Our results demonstrate the robustness of the bound states in a regime where exciton dissociation is otherwise expected, and offer promising perspectives in fundamental physics and in room-temperature applications involving high densities of charge carriers.

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“…The Mott criterion here predicts that the transition occurs if k S • a B ≃ 1.19, where k S is the critical screening length at which bound states nominally disappear and a B is the exciton Bohr radius [2]. More refined theoretical analysis [4,6] and extensive experimental work [7][8][9][10][11][12][13] have instead revealed a rich phase diagram of exotic states persisting above n M . Notable examples include robust excitonic and biexcitonic correlations [7][8][9], emergent Mahan excitons [10], anomalous metallic states [11], e-h droplets [12,13], and possible Bose condensates of photoexcited e-h Cooper pairs [4].…”

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confidence: 89%

Giant Exciton Mott Density in Anatase TiO2

et al. 2020

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Elucidating the carrier density at which strongly bound excitons dissociate into a plasma of uncorrelated electron-hole pairs is a central topic in the many-body physics of semiconductors. However, there is a lack of information on the high-density response of excitons absorbing in the near-to-mid ultraviolet, due to the absence of suitable experimental probes in this elusive spectral range. Here, we present a unique combination of many-body perturbation theory and state-of-the-art ultrafast broadband ultraviolet spectroscopy to unveil the interplay between the ultraviolet-absorbing two-dimensional excitons of anatase TiO 2 and a sea of electron-hole pairs. We discover that the critical density for the exciton Mott transition in this material is the highest ever reported in semiconductors. These results deepen our knowledge of the exciton Mott transition and pave the route toward the investigation of the exciton phase diagram in a variety of wide-gap insulators.

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Exciton Mott transition revisited

Cited by 40 publications

References 67 publications

Efficient evaluation of the polarization function in dynamical mean-field theory

Efficient evaluation of the polarization function in dynamical mean-field theory

Mahan excitons in room-temperature methylammonium lead bromide perovskites

Giant Exciton Mott Density in Anatase TiO2

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