First-Principles Research Of Thermal Spin Transport Properties In Structurally Tuned Quasi-Onedimensional Zigzag Graphene Nanoribbons

The integrated circuits play an irreplaceable role in the development of modern human society.However,with the advancement of technology,the heat generation and dissipation problems have become one of the bottlenecks in the development of the integrated circuits.In order to break the bottleneck,the spin caloritronics has been proposed,which combines the characteristics of thermoelectronics and spintronics,provides a new idea for the design of future integrated circuits.In spin caloritronics,the pure spin current with a charge current of zero and a spin current of non-zero can be obtained,leading to no heat generated by the charge current.Thus,the pure spin current devices are very important to solve the thermal problems in the development of integrated circuits.Devices fabricated based on spin caloritronics have greater advantages over traditional electronic devices in terms of computing speed,integration,and energy consumption.Based on the first-principles calculation,this thesis investigated how to achieve pure spin current in zigzag graphene nanoribbons,the main works are as follow:1.In this thesis,continuous antidots(hexagonal defects)are introduced at one edge of the zigzag graphene nanoribbons along the bandwidth direction.The results show that the introduction of antidots leads to an ‘X'-shape transmission spectrum around the Fermi energy level.Under a temperature field,the spin Seebeck coefficients around the Fermi energy level with opposite signs are obtained.Pure spin current could be induced by slightly tuning the chemical potential of the devices.For nanoribbons with W zigzag carbon chains,the maximum pure spin current could be obtained when the the number of the continuous antidots introduced along with the width of nanoribbons is(W/2-1).2.In this thesis,the zigzag-edged graphene nanoribbons with epitaxial isosceles triangle structure at one edge are studied,the ‘X'-shape transmission spectra around the Fermi energy level are formed.However,the slopes of the transmission spectra are too small to obtain a better pure spin current.Therefore,nanoribbons with epitaxial isosceles triangle structure on the two edges are proposed,it is found that the ‘X'-shape transmission spectra with larger slopes around the Fermi energy level are also preserved.Under a temperature field,the pure spin current could be obtained by slightly tuning the chemical potential of the devices.