First Principles Study On Thermal Spin Transport Of B And N Doped Zigzag Graphene Nanoribbons

Spintronics is a new subject using electronic intrinsic spin as information carrier.Compared with the traditional electronic devices using charge as information carrier,the new generation of spin electronic devices has many advantages,such as faster processing speed,lower power consumption and larger storage space.Combined with the advantages of thermoelectronics,we can design a spin thermoelectric device which can realize thermoelectric conversion.Because the internal spin current of the spin thermoelectric device is much larger than the charge current,it can greatly reduce the Joule heat generated by the internal charge current of the traditional circuit,greatly improve the working performance and reduce the thermal power consumption.Especially for the development of large scale integrated circuit technology,spin thermoelectric devices have extremely important research value and have attracted more and more researchers' attention.Therefore,the modulation of spin current is the central task of designing spin thermoelectric devices.Based on the first-principles calculation,the thermal spin transport is induced by doping multiple pairs of boron and nitrogen(BN)pairs at the edge of Zigzag graphene nanoribbons.The specific work can be divided into the following two aspects :(1)Design scheme of co-doped BN-NB pairs on the same edge of Zigzag graphene nanoribbons.The calculation results show that in the energy range near the Fermi level in the transmission spectrum,the curves of the two different spin channels show the cross of “X”.Therefore,after the temperature gradient is applied on the two electrodes of the device,the electrons with two different spins will be transported in the opposite direction,and then the spin current appears.Reflected in the spin Seebeck coefficient function,the two different spins at the Fermi level are always equal in size and opposite in sign.By slightly adjusting the chemical potential of the system,the pure spin current can be obtained and the perfect spin Seebeck effect can be realized.(2)A pair of BN pairs were doped on the two edges of Zigzag graphene nanoribbons,and the two impurities gradually moved towards the middle.The calculation results show that when and only when the two BN pairs are doped at the edge of the nanoribbon,there will be a “X”-shaped transport cross near the Fermi level of the transmission spectrum,and a stable spin current is obtained.Further increasing the number of BN pairs to become BN chains,the “X” shape transport cross still exists,and the spin Seebeck power is further improved.Driven by the temperature gradient,a stable pure spin current is obtained by fine tuning the chemical potential.