Chemical control of the Rashba spin splitting size of α -GeTe(111) surface states by adjusting the potential at the topmost atomic layer

Abstract

As control of the Rashba spin splitting size is highly desirable for spintronic devices, intensive studies have been performed to vary the splitting size by, for example, applying an electric field or designing novel heterostructures. However, direct observation of Rashba spin splitting size change via spectroscopic measurements has not been done so far. Here, we report results of angle-resolved photoemission studies on ferroelectric α-GeTe(111). We observe that the Rashba splitting size of α-GeTe(111) surface states is reduced upon dosing with potassium (K) which has a very low electron affinity. Based on density functional theory calculations, we find that the electric potential energy at the topmost atomic layer and the surface potential energy barrier is reduced upon K dosing. This change in the surface potential induces both delocalization of the surface states and reduction of the splitting size. We expect to increase the splitting size by dosing other elements or molecules with high electron affinity.

Spin Dynamics Modulated by Rashba States in Ferroelectric α-GeTe

“…Due to the bulk doping of Bi element, the potential energy at the topmost atomic layers is almost unchanged with increasing Bi concentration, hence, is nearly the same in all samples. Compared to other works revealing the desperation of surface Rashba states 20,21 , the Rashba splitting size of SSs decreased with K doping 20 , which put the spintronics application and Rashba related research of -GeTe under an adverse circumstance. In our experiment, as elevatoring Bi concentration, the splitting size of both bulk and surface Rashba are nearly unchanged, comparing with the undoped sample.…”

“…In addition to the bulk Rashba states, the surface state of -GeTe is Rashba state as well, and has a sizeable Rashba splitting size, which may give rise to the unique performance on the magnetic dynamics. Recently, the whole surface Rashba dispersions have been realized by doping potassium (K) atoms on the surface of -GeTe 20,21 , implying that doping electrons can raise the FL. However, the reduced size of surface Rashba splitting by doping K limits the Rashba applications and the related research 20 .…”

“…Recently, the whole surface Rashba dispersions have been realized by doping potassium (K) atoms on the surface of -GeTe 20,21 , implying that doping electrons can raise the FL. However, the reduced size of surface Rashba splitting by doping K limits the Rashba applications and the related research 20 . Alternately, doping Bi or Sb atoms in -GeTe gains a super-high thermoelectric gure-of-merit, and increases the resistance as well 22 .…”