Room Temperature Charge-Spin Interconversion in a Topological Insulator and Graphene Heterostructure
Typ
Examensarbete för masterexamen
Program
Nanotechnology (MPNAT), MSc
Publicerad
2022
Författare
Sjöström, Lars
Modellbyggare
Tidskriftstitel
ISSN
Volymtitel
Utgivare
Sammanfattning
The main goal of spintronics is to utilise the spin degree of freedom beyond conventional
charge-based technologies and make faster and less energy-consuming nonvolatile
information technology. To realise this, efficient generation, transport and
detection of polarised spin are necessary. Topological insulators are emerging materials
for spin generation and detection in all-electrical spintronics applications,
thanks to their strong spin-orbit coupling and the non-trivial spin-momentum locking
of their unique topological surface states. Due to the efficient charge-to-spin conversion
process, applying a bias current to induce a net carrier momentum should
spontaneously generate a net spin polarisation in such a system. However, while
charge-spin interconversion in topological insulators has previously been reported,
reliable non-local measurements have so far been limited to cryogenic temperatures.
In this master’s thesis, charge-to-spin and spin-to-charge conversion in the topological
insulator Bi1.5Sb0.5Te1.7Se1.3 are detected in a non-local measurement method
at room temperature, using a van der Waals heterostructure with a graphene spin
valve device. These heterostructures make it possible to combine the spin polarisation
of the topological insulator with the excellent spin transport properties of
graphene. The observation of both spin switch and Hanle spin precession signals in
the non-local geometry and detailed bias- and gate-dependent measurements prove
the robustness of the charge-spin interconversion effects in topological insulators at
room temperature. These findings demonstrate the possibility of using topological
insulators to make all-electrical room-temperature spintronics devices.
Beskrivning
Ämne/nyckelord
spintronics, topological insulator, Bi1.5Sb0.5Te1.7Se1.3, charge-spin interconversion, room temperature, van der Waals heterostructure, graphene, spin valve, spin switch, Hanle spin precession