ELFT HÍRADÓ

[Janos Asboth <asboth.janos AT wigner.mta.hu>]

Kedves Kollégák!

A Wigner FK SZFI Kvantumoptika és Kvantuminformatika Osztályának
szemináriuma

-   szeptember 7, csütörtök, 13:00
-   MTA Wigner FK SZFI, I. épület 1. emeleti Tanácsterem

  Emilie Bruyer (Institut des Sciences Chimiques de Rennes, France):
*Epitaxially-strained GeTe as a prototype material for a microscopic
understanding of bulk Rashba properties*

                  - abstract: -
Relativistic effects are increasingly seen as key ingredients in the
burgeoning field of spintronics. Among them, the Rashba effect, in which
the spin degeneracy is removed as a consequence of spin-orbit coupling
(SOC) in noncentrosymmetric structures, plays a leading role. An
interesting subclass of bulk materials lacking inversion symmetry is
represented by ferroelectrics, which could in principle allow to bring in a
novel functionality through the interplay between ferroelectricity and
SOC-induced Rashba spin-splitting (RSS). For such materials, the coupling
of RSS with electric polarization opens up a wide range of potential
applications in the field of semiconductor spintronics, aiming at an
all-electric control of spin transport in novel devices. In this context,
many efforts are now given in the search for such multifunctional materials
and strain engineering is nowadays regarded as a powerful tool to tune
these highly desirable properties.

Using first-principles calculations, we simulated a (111)
epitaxially-strained growth and computed the changes in the structural,
electronic and magnetic behaviour of GeTe, a ferroelectric material known
to also exhibit a wide bulk RSS. Interestingly, our results showed that RSS
could not be driven by the sole modification of the ferroelectric
polarization and the electronic band gap, as usually believed. Further DFT
calculations and the elaboration of a tight-binding model lead to the
identification of the main parameters entering the strength of RSS and
identify their contribution. This study indicates that the RSS is not only
strongly k-dependent, but also very sensitive to the orbital character of
the bands around the Fermi level.

Our findings highlight the decisive influence of the electronic structure
on spin-orbital properties and the need of a deep understanding of these
features for each multifunctional material.


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Asbóth János