Dielectric constant and soft mode of Pb1−xSnxTe

Effect of band inversion on the phonon spectra of Hg 1– x Zn x Te and Hg 1– x Cd x Te semiconductor alloys

“…The temperature dependence of ω TO of HgTe-like mode has a minimum at T=110 K, near the inversion point. This result is in agreement with the theory prediction [2]. According to [2], the self energy of TO-phonon obtained from the solution of total Hamiltonian for Bloch electrons and TO-phonons in view of electron-phonon coupling has minimal value at the inversion point of the valence and conduction band.…”

“…In conclusion, a reduction of TO and coupled plasmon-LO-phonon HgTe-like modes was observed near the inversion point in the Hg 0.9 Zn 0.1 Te alloy. Results are in a qualitative agreement with theory for narrow-gap IV-VI compounds [2] while a new model have to be proposed for II-VI compounds to explain experimental data.…”

“…After a band inversion the alloys become semimetal, moreover at the inversion point all three bands cross at the Γ-point. The reduction of the TO-phonon frequency near the inversion point, due to an electronphonon coupling was theoretically predicted by Kawamura et al for narrow-gap IV-VI compounds [2]. According to the proposed model, when a deformation due to optical modes is applied, the nearly degenerate levels split, and the energy gap increases.…”

Femtosecond pump–probe study of coherent soft phonon in Pb1−Ge Te ferroelectrics

“…With increasing the pump fluence, the frequency of the A 1 mode significantly decreases from 0.86 to 0.57 THz. Similar to the coherent A 1g phonon in another narrow band gap ferroelectric GeTe [10], the softening of A 1 mode in Pb 1Àx Ge x Te would be due to the electron-phonon coupling via optical deformation potential interaction [11,12] and/or anharmonic phonon-phonon interactions [13,14]. When the pump fluence reaches 2.4 mJ/cm 2 , the frequency of the coherent A 1 phonon exhibits saturation behavior.…”

Synchrotron radiation – a brilliant source for solid‐state research in the infrared energy domain

“…Actually, the zero-gap state in the MCT alloys determines a singularity in the phonon spectrum and not a ''softening'' of the phonon mode as proposed in Ref. [29].…”