Skip to Main content Skip to Navigation
Theses

Ab initio investigations of spin-dependent quantum transport

Abstract : Spintronics devices manipulate the electron spin degree of freedom to process information. In this thesis, we investigate spin-dependent quantum transport properties to optimize the performances of spintronics devices. Through ab initio approach, we research the tunneling magnetoresistance (TMR), spin Hall effect (SHE), as well as spin injection efficiency (SIE). It has been demonstrated that heavy metals (HMs) are able to modulate TMR effects in MgO-based magnetic tunnel junctions (MTJs), and tungsten, molybdenum, and iridium are promising to enhance TMR. Moreover, substitutional atom doping can effectively optimize SHE of HMs, which would strengthen spin Hall angles (SHAs) to achieve efficient spin-orbit torque (SOT) switching of MTJs. To eliminate the mismatch between ferromagnetic and barrier layers in MgO-based MTJs, we design the MTJ with bond-free van der Waals (vdW) heterojunction VSe₂/MoS₂ and report the room-temperature TMR. The occurrence of quantum-well resonances enables voltage control to be an effective method to modulate TMR ratios in vdW MTJ. We put forward the idea of SOT vdW MTJ, which employs SOT to switch vdW MTJ and requires vdW materials with strong SHE. Research on MoTe₂ and WTe₂ verifies the possibility of realizing this idea. Both of them are layered transition metal dichalcogenides (TMDC) and exhibit strong SHEs, as well as large SHAs thanks to their low electrical conductivity. Lastly, motivated by the demand of a two-dimensional (2D) switchable device with long spin diffusion length, we construct the spin injection system with silicene monolayer, and reveal high SIEs under electric fields. Works in this thesis would advance the research of spintronics devices.
Complete list of metadatas

https://tel.archives-ouvertes.fr/tel-02459090
Contributor : Abes Star :  Contact
Submitted on : Wednesday, January 29, 2020 - 10:46:15 AM
Last modification on : Tuesday, September 29, 2020 - 4:43:54 AM
Long-term archiving on: : Thursday, April 30, 2020 - 1:50:55 PM

File

84733_ZHOU_2019_diffusion.pdf
Version validated by the jury (STAR)

Identifiers

  • HAL Id : tel-02459090, version 1

Citation

Jiaqi Zhou. Ab initio investigations of spin-dependent quantum transport. Micro and nanotechnologies/Microelectronics. Université Paris Saclay (COmUE); Beihang university (Pékin), 2019. English. ⟨NNT : 2019SACLS508⟩. ⟨tel-02459090⟩

Share

Metrics

Record views

96

Files downloads

36