Quantum Theory of the Optical and Electronic Properties of Semiconductors

Narlikar, Jayant V.

doi:10.1142/2451

Cited by 574 publications

(720 citation statements)

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“…While elastic scattering of excitons with free carriers causes a spectral broadening of the excitonic features, screening and Pauli blocking cause a spectral shift 41,[47][48][49][50] . Screening of the e-h interactions lowers the exciton binding energy, whereas screening of the electron-electron (e-e) interactions induces a decrease of the quasi-particle self-energy and a band-gap renormalization to lower energies [48][49][50] .…”

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confidence: 99%

Probing the Spin-Polarized Electronic Band Structure in Monolayer Transition Metal Dichalcogenides by Optical Spectroscopy

et al. 2017

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We study the electronic band structure in the K/K' valleys of the Brillouin zone of monolayer WSe 2 and MoSe 2 by optical reflection and photoluminescence spectroscopy on dual-gated field-effect devices. Our experiment reveals the distinct spin polarization in the conduction bands of these compounds by a systematic study of the doping dependence of the A and B excitonic resonances. Electrons in the highest-energy valence band and the lowest-energy conduction band have antiparallel spins in monolayer WSe 2 , and parallel spins in monolayer MoSe 2 . The spin splitting is determined to be hundreds of meV for the valence bands and tens of meV for the conduction bands, which are in good agreement with first principles calculations. These values also suggest that both n-and ptype WSe 2 and MoSe 2 can be relevant for spin-and valley-based applications.

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confidence: 99%

Probing the Spin-Polarized Electronic Band Structure in Monolayer Transition Metal Dichalcogenides by Optical Spectroscopy

et al. 2017

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“…An electric field leads to several modifications of the absorption spectrum: 1) modulation of the absorption coefficient; 2) growth of the band-to-band absorption spectral weight; 3) shift of the absorption peak, known as the Stark effect; and 4) dissociation of the bound exciton. In bulk 3D semiconductors the binding energy is small and most of the theoretical and experimental focus has been on the field induced absorption in the region below the bandgap and on the quantum confined Stark effect in 2D structures [13]. In carbon nanotubes, the binding energy is large and the oscillator strength of the higher lying Rydberg states is infinitesimal, so that relatively large changes in the absorption at the first excitonic peak and the first band-to-band absorption are expected.…”

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confidence: 99%

Exciton Ionization, Franz−Keldysh, and Stark Effects in Carbon Nanotubes

Perebeinos¹,

2007

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We calculate the optical properties of carbon nanotubes in an external static electric field directed along the tube axis. We predict strong Franz-Keldysh oscillations in the first and second band-toband absorption peaks, quadratic Stark effect of the first two excitons, and the field dependence of the bound exciton ionization rate for a wide range of tube chiralities. We find that the phonon assisted mechanism dominates the dissociation rate in electro-optical devices due to the hot optical phonons. We predict a quadratic dependence of the Sommerfeld factor on the electric field and its increase up to 2000% at the critical field of the full exciton dissociation.Semiconducting carbon nanotubes are direct bandgap materials which have attracted much attention recently for nanophotonic applications [1]. Almost fifty years ago Franz and Keldysh predicted that a static electric field would modify the linear optical properties of the 3D semiconductors near their absorption edge [2, 3]. They showed that the absorption coefficient decays exponentially for photons below the bandgap and shows oscillations for energies above the bandgap.The interest in electroabsorption was revived about three decades latter after discovery of the Quantum-Confined Stark Effect in 2D quantum well structures [4,5]. Large Stark shifts were observed in fields directed perpendicular to the 2D planes. In 1D carbon nanotubes, excitons were predicted to have large binding energies [6] and to dominate the absorption spectra [7,8], a fact which was verified experimentally by two-photon spectroscopy [9,10] and from the observation of the phonon sidebands in photoconductivity spectra [11]. The exciton binding energies in carbon nanotubes have interesting scaling properties [8] and they can be as small as those in 2D structures and as large as 30% of their bandgap depending on both the nanotube structure and the environment.It has been long recognized that excitonic effects enhance significantly the electroabsorption sig-

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“…2.1) the microscopic access to the temporal evolution of an arbitrary operator quantity x(t) within the Heisenberg equation of motion is given by [51] …”

Section: Microscopic Bloch Equationmentioning

confidence: 99%

“…The temporal evolution for the appearing two-particle quantities depends on three-particle terms , which couple to four-particle quantities, and so on. To obtain a nite set of equations, the in nite hierarchy needs to be systematically truncated at some level by exploiting the correlation expansion [51]. The n-th order expectation value is factorized into all possible permutations of correlated expectation values of the same and lower order correlations:…”

Section: Microscopic Bloch Equationmentioning

confidence: 99%

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Relaxation Dynamics in Graphene

Malić

Knorr

2013

Graphene and Carbon Nanotubes

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In this thesis, the relaxation dynamics of nonequilibrium carriers in graphene is investigated. Based on the density matrix approach, the interaction of carriers with light, phonons and electrons is theoretically modelled. The resulting time-, momentum-, and angle-resolved simulation of the carrier dynamics enables the interpretation of recent experimental observations. Typically, the carrier relaxation has been accessed via high-resolution pump-probe experiments. Common to all studies is a bi-exponential decay of the pump-induced differential transmission (DT) spectrum. The fast decay component in the range of few tens of femtoseconds is assigned to an ultrafast Coulomb-dominated carrier redistribution towards a hot Fermi-Dirac distribution, whereas the slower decay component in the range of a picosecond reflects the equilibration between the electron and the phonon system. However, many studies report a zero-crossing after the initial decay in the transient DT spectrum, where the second decay component characterizes the recovering of the DT signal. In very good agreement with recent pump-probe experiment performed by the group of Prof. Manfred Helm (Helmholtz-Zentrum Dresden-Rossendorf), a microscopic explanation for the occurrence of transient negative differential transmission in graphene is found, where a detailed interplay of intraand interband absorption processes on the transient DT in graphene is investigated. In particular, phonon-assisted intraband processes are shown to lead to an enhanced absorption giving rise to the experimentally observed zero-crossing from positive to negative DT signals.In collaboration with the group of Prof. Theodore B. Norris (Michigan University, USA), theoretical studies combined with ultrafast time-resolved THz spectroscopy were performed to systematically investigate the hot-carrier dynamics in an array of graphene samples. The theory calculates explicitly the time-dependent response of the system to a THz probe pulse. The calculations reveal that the observed dynamics can be accounted for qualitatively without including any fitting parameters, phenomenological models or extrinsic effects. Specifically, the hot-carrier dynamics are governed by the coupling of extraordinarily efficient carrier-carrier and carrier-phonon interactions. Furthermore, the theory demonstrates that the simple Drude model is insufficient to fully account for the THz interactions.Beside pump-probe studies, the thesis presents the absorption spectra of mono-and bilayer graphene including the impact of the fully momentum-dependent optical and Coulomb matrix elements. In agreement with recent experiments, the absorbance of graphene is characterized by a frequency-independent value in the near-infrared spectral region and a pronounced peak in the ultraviolet region resulting from interband transition. In contrast to the linear band structure of graphene, the energy dispersion of bilayer graphene exhibits four parabolic bands resulting in interesting optical features: The absorbance exhibits in...

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Quantum Theory of the Optical and Electronic Properties of Semiconductors

Cited by 574 publications

References 0 publications

Probing the Spin-Polarized Electronic Band Structure in Monolayer Transition Metal Dichalcogenides by Optical Spectroscopy

Probing the Spin-Polarized Electronic Band Structure in Monolayer Transition Metal Dichalcogenides by Optical Spectroscopy

Exciton Ionization, Franz−Keldysh, and Stark Effects in Carbon Nanotubes

Relaxation Dynamics in Graphene

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