Temperature Dependence of Exciton Linewidth in CsI and CsBr

Abstract

The temperature dependence of the linewidth of the lowest two r; excitons in Csl and in CsBr and of a very narrow I ? ; exciton in CsI is reported. All spectra are measured by three-photon spectroscopy. The analysis of the experimental results allows conclusions about the decay mechanism of excitons in alkali halides. The temperature dependent broadening is quantitatively described by taking into account exciton-phonon interaction.Die Temperaturabhiingigkeit der Linienbreiten der beiden niederenergetischen r;-Exzitonen in CsI und CsBr und eines sehr schmalen r;-Exzitons in CsI wird untersucht. Alle Spektren werden mit der Methode der Dreiphotonenspektroskopie ausgemessen. Die Auswertung der experimentellen Resultate erlaubt Ruckschliisse auf den Zerfdlsmechanismus der Exzitonen in Alkalihalogeniden.Unter Einbeziehung der Exziton-Phonon-Wechselwirkung kann die temperaturabhiingige Linienverbreiterung quantitativ beschrieben werden.

Band-structure parameters and Fermi resonances of exciton-polaritons in CsI and CsBr under hydrostatic pressure

“…Others have also tried in vain to find this excitation [27]. Nevertheless, the spectral narrowing of the lowest state A as observed for CsI [28] was also observed for CsBr with increasing pressure -though not as dramatic as for CsI.…”

“…The critical pressure in CsBr for the point of closest approach appears to be at about 6 kbar. The lowest energy paraexciton band (C) was not detected [27]. At zero pressure the longitudinal energies are approximately: 6.965 eV (A),…”

Exciton absorption spectrum of thin CsPbI3 and Cs4PbI6 films

“…We do not know the បω LO values for CsPbI 3 and Cs 4 PbI 6 . They can be estimated based on the known parameters បω LO = 13.7 meV for PbI 2 [18] and បω LO = 11 meV in CsI [19]. With allowance for the molar contents of the compo sitions, បω LO ∼ 12.35 meV for CsPbI 3 and 11.54 meV for Cs 4 PbI 6 .…”

Exciton-phonon interaction in the strong-coupling regime in hexagonal boron nitride

“…Before further discussing the specificity of phononassisted broadening in a Van der Waals crystal such as hBN, we aim at comparing with the standard expression used in the weak coupling regime for Lorentzian lines: the FWHM is fitted in that case by Γ 0 +aT +b/(exp(E O /k B T ) − 1), where the last two terms account for acoustic and optical phonon broadening, respectively [6,[8][9][10][11][12][13][14][15][16][17]. The best fit is displayed in dashed line in Fig.3, and we find Γ 0 =3±0.5 meV, a=0.1±0.02 meV/K, b=150±80 meV and E O =25±10 meV.…”