فرزانه قاسم زاده

Borophene, owing to the high mobility and long spin coherent length of its carriers, offers significant opportunities for advancement in ultra-fast spintronics. In this research, we investigate the spin-dependent conductance a Datta–Das field-effect transistor (FET) boron-based nanoribbon using a tight-binding Hamiltonian with a non-equilibrium Green’s function approach. The spin FET electrodes are magnetized by ferromagnetic (FM) insulators arranged in both parallel and anti-parallel configurations. This device acts as a controllable spin filter in the presence of spin-orbit coupling and its spin current is effectively modulated by the gate voltage and the strength of spin-orbit coupling. For the anti-parallel configuration, an energy gap appears within a specific range of the electron energy, which can be vanished for electrons with spin under spin-orbit coupling. Moreover, our findings indicate that electron-electron (e-e) interactions contribute to the initial spin transport of injected electrons in the transistor channel, thereby enhancing the spin-orbit coupling effect. It is worth noting that a gate voltage can adjust the device’s current-voltage (I-V) characteristics. The current and Ion/Ioff ratios of boron-based spin field-effect transistors are several times higher than those of graphene and silicene spin field-effect transistors under the same conditions. Furthermore, the integration of spintronics with thermoelectrics has led to the emergence of a new research field known as spin caloritronics. This feature enables us to generate spin current with a lower energy consumption technology using a temperature gradient. Therefore, we intend to investigate the spin-thermal and spin Seebeck effects of a zigzag boron nanowire in a normal-ferromagnetic-normal junction. Our results demonstrate that a pure spin current can be generated by an appropriate temperature gradient, resulting from electrons and non-magnetic holes in the boron nanowire. This phenomenon is accompanied by the emergence of a Seebeck coefficient with opposite signs for spin-up and spin-down, which induces a pure spin voltage in this system. The spin currents and thermal loads at low temperatures operate like a thermoelectric diode. Additionally, this system can provide complete spin separation. To eva‎luate the spin-dependent thermoelectric performance, we calculate the spin figure of merit and spin efficiency. We find that significantly increasing the spin figure of merit is achievable by enhancing the exchange field strength in the leads. Furthermore, we show that the spin figure of merit depends on the nanowire width and increases with a decrease in the nanowire width. Our findings indicate that boron nanowires are suitable materials for spintronic thermoelectric devices. Since the amorphous phase of boron is known as borophene and possesses these remarkable properties, we have investigated the spin-dependent effects for boron nanowires and compared them with borophene in its flat phase. Considering these significant and distinctive properties of boron, we have decided to finally examine the sensing properties of a single-layer boron hydrogenide (B8H4) using the density functional theory approach.

بروفين، ترانزيستورهاي اثر ميداني، جفت شدگي اسپين-مدار راشبا، رسانش اسپيني، اسپين كالريترونيك، اثر سيبك

Borophene, Spin Field-Effect Transistors, Spin-Orbit Coupling, Spin Transport, Spin Caloritronics, Spin Seebeck Effect

Farzaneh Ghasemzadeh

Professor Mahdi Esmaeilzadeh