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ETSF online seminar by Norma Rivano: Friday Janu ... (No replies)

4 years ago

berger 4 years ago

Dear colleagues,

The next ETSF seminar will be given by Norma Rivano from the Ecole Polytechnique de Lausanne, on Friday January 28 at 14:00 CET.

The title of the talk is “Breakdown of LO-TO polar splitting in 1D materials and its application to nanowire and nanotubes”.

Below you will find an abstract of the seminar.

All ETSF members will receive an email with a zoom link a couple of days before the seminar.

If you are not an ETSF member and you would like to follow the seminar please send an email to [email protected].

Best wishes,
Arjan Berger

Abstract:

Accurate models and simulations of the vibrational properties of 1D materials are crucial for

the analysis and prediction of transport and spectroscopic properties. In the long-wavelength

limit, longitudinal polar-optical phonons (those probed by IR and Raman spectroscopies) are

known to undergo a frequency shift which depends strongly on dimensionality. In 3D, this leads

to a roughly constant separation between the optical modes across the Brillouin zone, termed

LO-TO splitting. At variance, in 2D the dielectric shift has been shown to depend upon the

phonon wavevector and to linearly vanish at small momenta [1]. Using analytical models and

density-functional perturbation theory in a newly-implemented one-dimensional framework, we

show that it also vanishes in 1D, but with a logarithmic asymptotic behavior. We highlight this

by studying a BN atomic-chain, BN armchair nanotubes and GaAs nanowires of varying size.

We also discuss the polar and mechanical nature of the phonon energy shift and its dependency

on dimensionality. In my talk I will discuss how this work not only provides useful insight into

the vibrational physics of a wide class of 1D materials, but also a ready-to-use tool for the

experimental community to encourage further studies.

[1] T. Sohier, M. Gibertini, M. Calandra, F. Mauri, and N. Marzari, Nano Lett. 17, 3758 (2017).