arXiv subjects

S. V. Koniakhin

Publications and source records attributed to S. V. Koniakhin.

21 records · Page 2Linked to original sources

arXiv2016

Drag of electrons in graphene by substrate surface polar phonons

It is known that electron scattering by surface polar phonons (SPPs) of the substrate reduces their mobility in supported graphene. However, there is no experimental evidence for contribution of drag of electrons by SPP to thermoelectric phenomena in graphene: graphene thermopower exhibits good agreement with Mott's law, which means that the diffusion contribution to the thermopower is dominant in a wide range of carrier densities and temperatures. Here we develop a complete theory of drag of electrons in graphene by SPP. By solving Boltzmann transport equation for electrons scattered by SPPs we derive SPP drag contribution to the thermopower in graphene. Compared to diffusion thermopower, obtained values appear to be one order of magnitude lower for various substrates. This can be explained by low occupation number of the SPPs and short mean free path of such phonons stemming from their small group velocity. We conclude that experiments on thermopower in graphene can be treated within the framework of Mott's law.

cond-mat.mes-hall↗

arXiv2016

New explanation of Raman peak redshift in nanoparticles

In this letter, we propose a new model that explains the Raman peak downshift observed in nanoparticles with respect to bulk materials. The proposed model takes into account discreteness of the vibrational spectra of nanoparticles. For crystals with a cubic lattice (Diamond, Silicon, Germanium) we give a relation between the displacement of Raman peak position and the size of nanoparticles. The proposed model does not include any uncertain parameters, unlike the conventionally used phonon confinement model (PCM), and can be employed for unambiguous nanoparticles size estimation.

cond-mat.mes-hall↗

arXiv2015

Phonon drag thermopower in graphene in equipartition regime

This letter calculates the contribution of electron-phonon interaction to thermoelectric effects in graphene. One considers the case of free standing graphene taking into account interaction with intrinsic acoustic phonons. The temperatures considered range from liquid nitrogen to the room level. It has turned out that the contribution to thermoelectromotive force due to electron drag by phonons is determined by the Fermi energy in the sample and phonon relaxation time. The explicit temperature dependence of the contribution to thermoelectromotive force deriving from by phonons is weak in contrast to that due to diffusion, which is directly proportional to temperature. The dependence obtained suggests that at the temperatures considered, a high carrier concentration and for samples with a high thermal conductivity, the phonon drag contribution can become dominant. Thus a theoretical limit has been established for a possible increase of the thermoelectromotive force through electron drag by the intrinsic phonons of graphene.

cond-mat.mes-hall↗