Excitonic correlation in the Mott crossover regime in Ge

Sekiguchi, Fumiya; Shimano, Ryo

doi:10.1103/physrevb.91.155202

Cited by 29 publications

(27 citation statements)

References 52 publications

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“…However, within a few nanoseconds the contribution of the electron-hole plasma vanishes. Simultaneously, we observe the formation of excitons as indicated by the occurrence of a prominent absorption peak around 3.1 meV which is associated with the intra-excitonic 1s-2p transition and agrees with earlier findings [22]. An additional absorption resonance appears at 2.4 meV which is accompanied by an oscillatory signature of the dielectric function.…”

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confidence: 92%

Density-dependent exciton dynamics and L -valley anisotropy in germanium

et al. 2017

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Optical pump-THz probe spectroscopy is used to investigate the exciton formation dynamics and its intensity dependence in bulk Ge. Associated with the intra-excitonic 1s-2p transition, the gradual build-up of an absorption peak around 3.1 meV (0.75 THz) signifies the delayed exciton formation after optical pump which is accelerated for higher excitation densities. Analyzing the spectral shape of this THz absorption resonance, two distinct resonances are found which are attributed to the mass-anisotropy of L valley electrons via a microscopic theory.

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Density-dependent exciton dynamics and L -valley anisotropy in germanium

et al. 2017

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“…One can find a close relation between EMT and Mott transition in the half-filled single-band Hubbard model, identifying the IMT in the latter case as the dissociation of bound doublons and holons [3,4]. EMT has long been investigated from the viewpoint of optoelectronic applications as well as of quantum many-body physics [5][6][7][8][9][10][11][12][13][14], nevertheless the fundamental nature of EMT remains unresolved. Mott suggested that at zero temperature the number of free charge carriers is discontinuous across the IMT and the transition has to be inherently first order.…”

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Anomalous Metal Phase Emergent on the Verge of an Exciton Mott Transition

et al. 2017

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We investigate the exciton Mott transition (EMT) by using optical pump-terahertz probe spectroscopy on GaAs, with realizing the condition of Mott's gedanken experiment by the resonant excitation of 1s excitons. We show that an anomalous metallic phase emerges on the verge of the EMT as manifested by a peculiar enhancement of the quasiparticle mass and scattering rate. From the temperature and density dependence, the observed anomaly is shown to originate from the electron-hole (e-h) correlation which becomes prominent at low temperatures, possibly suggesting a precursor of e-h Cooper pairing.

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“…photoluminescence spectroscopy. [30][31][32][33] Recent terahertz spectroscopy has shed new light on this problem, [34][35][36][37] making it possible to determine the exciton ionization ratio through the quantitative evaluation of excitons and unbound eh pairs densities. In particular, our recent study on the ultrafast dynamics of EMT in GaAs under the resonant excitation of excitons has indicated the signature of first-order phase transition.…”

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Rate Equation Analysis of the Dynamics of First-order Exciton Mott Transition

Sekiguchi

Shimano

2017

J. Phys. Soc. Jpn.

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We performed a rate equation analysis on the dynamics of exciton Mott transition (EMT) with assuming a detailed balance between excitons and unbound electron-hole (e-h) pairs. Based on the Saha equation with taking into account the empirical expression for the band-gap renormalization effect caused by the unbound e-h pairs, we show that the ionization ratio of excitons exhibits a bistability as a function of total e-h pair density at low temperatures. We demonstrate that an incubation time emerges in the dynamics of EMT from oversaturated exciton gas phase on the verge of the bistable region. The incubation time shows a slowing down behavior when the pair density approaches toward the saddle-node bifurcation of the hysteresis curve of the exciton ionization ratio.Photocontrol of condensed matter systems has gained continuing interests over decades, [1][2][3] e.g. in semiconductors, 4,5) Mott insulators, 3,6-9) spin crossover complexes, [10][11][12] and superconductors. 13,14) Among diverse material systems, photoexcited electron-hole (e-h) systems in semiconductors offer a unique arena to study the rich variety of phases emergent in many particle systems, and their non-equilibrium dynamics. 4,15) One of the intriguing aspects of e-h systems is that the strength of inter-particle Coulomb interaction can be effectively controlled by changing the density of photoexcited carriers through the screening effect, by simply changing the excitation light intensity. The change of the Coulomb interaction causes a phase transition, or crossover, from the insulating exciton gas phase in the low density regime to the metallic e-h plasma in the high density regime, referred to as exciton Mott transition (EMT). There is a long-standing argument whether EMT is a crossover or a first-order phase transition accompanied by a bistability at sufficiently low temperatures. [16][17][18][19][20][21][22] In general, bistability appears in diverse systems such as electronic circuits, optoelectronic systems, magnetic systems, molecular and biological systems, etc. Figure

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Excitonic correlation in the Mott crossover regime in Ge

Cited by 29 publications

References 52 publications

Density-dependent exciton dynamics and L -valley anisotropy in germanium

Density-dependent exciton dynamics and L -valley anisotropy in germanium

Anomalous Metal Phase Emergent on the Verge of an Exciton Mott Transition

Rate Equation Analysis of the Dynamics of First-order Exciton Mott Transition

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