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Register a new userResonant tunneling diode with spin polarized injector
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We investigate the current-voltage characteristics of a II-VI semiconductor resonant-tunneling diode coupled to a diluted magnetic semiconductor injector. As a result of an external magnetic field, a giant Zeeman splitting develops in the injector, which modifies the band structure of the device, strongly affecting the transport properties. We find a large increase in peak amplitude accompanied by a shift of the resonance to higher voltages with increasing fields. We discuss a model which shows that the effect arises from a combination of three-dimensional incident distribution, giant Zeeman spin splitting and broad resonance linewidth.
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We study I-V characteristics of an all-II-VI semiconductor resonant tunneling diode with dilute magnetic impurities in the quantum well layer. Bound magnetic polaron states form in the vicinity of potential fluctuations at the well interface while tunneling electrons traverse these interface quantum dots. The resulting microscopic magnetic order lifts the degeneracy of the resonant tunneling states. Although there is no macroscopic magnetization, the resulting resonant tunneling current is highly spin polarized at zero magnetic field due to the zero field splitting. Detailed modeling demonstrates that the local spin polarization efficiency exceeds 90% without an external magnetic field.
A method for measuring the degree of spin polarization of magnetic materials based on spin-dependent resonant tunneling is proposed. The device we consider is a ballistic double-barrier resonant structure consisting of a ferromagnetic layer embedded between two insulating barriers. A simple procedure, based on a detailed analysis of the differential conductance, allows to accurately determine the polarization of the ferromagnet. The spin-filtering character of such a system is furthermore addressed. We show that a 100% spin selectivity can be achieved under appropriate conditions. This approach is believed to be well suited for the investigation of diluted magnetic semiconductor heterostructures.
We investigate interlayer tunneling in heterostructures consisting of two tungsten diselenide (WSe2) monolayers with controlled rotational alignment, and separated by hexagonal boron nitride. In samples where the two WSe2 monolayers are rotationally aligned we observe resonant tunneling, manifested by a large conductance and negative differential resistance in the vicinity of zero interlayer bias, which stem from energy- and momentum-conserving tunneling. Because the spin-orbit coupling leads to coupled spin-valley degrees of freedom, the twist between the two WSe2 monolayers allows us to probe the conservation of spin-valley degree of freedom in tunneling. In heterostructures where the two WSe2 monolayers have a 180{deg} relative twist, such that the Brillouin zone of one layer is aligned with the time-reversed Brillouin zone of the opposite layer, the resonant tunneling between the layers is suppressed. These findings provide evidence that in addition to momentum, the spin-valley degree of freedom is also conserved in vertical transport.
We propose an electrically driven spin injector into normal metals and semiconductors, which is based on a magnetic tunnel junction (MTJ) subjected to a microwave voltage. Efficient functioning of such an injector is provided by electrically induced magnetization precession in the free layer of MTJ, which generates the spin pumping into a metallic or semiconducting overlayer. We theoretically describe the spin and charge dynamics in the CoFeB/MgO/CoFeB/Au(GaAs) heterostructures. First, the magnedynamics in the free CoFeB layer is quantified with the account of a spin-transfer torque and a voltage-controlled magnetic anisotropy. By numerically solving the magnetodynamics equation, we determine dependences of the precession amplitude on the frequency $f$ and magnitude $V_mathrm{max}$ of the ac voltage applied to the MTJ. It is found that the frequency dependence changes drastically above the threshold amplitude $V_mathrm{max} approx 200$mV, exhibiting a break at the resonance frequency $f_mathrm{res}$ due to nonlinear effects. The results obtained for the magnetization dynamics are used to describe the spin injection and pumping into the Au and GaAs overlayers. Since the generated spin current creates additional charge current owing to the inverse spin Hall effect, we also calculate distribution of the electric potential in the thick Au overlayer. The calculations show that the arising transverse voltage becomes experimentally measurable at $f = f_mathrm{res}$. Finally, we evaluate the spin accumulation in a long n$^+$-GaAs bar coupled to the MTJ and determine its temporal variation and spatial distribution along the bar. It is found that the spin accumulation under resonant excitation is large enough for experimental detection even at micrometer distances from the MTJ. This result demonstrates high efficiency of the described nanoscale spin injector.
We report on the realization of a double barrier resonant tunneling diode for cavity polaritons, by lateral patterning of a one-dimensional cavity. Sharp transmission resonances are demonstrated when sending a polariton flow onto the device. We use a non-resonant beam can be used as an optical gate and control the device transmission. Finally we evidence distortion of the transmission profile when going to the high density regime, signature of polariton-polariton interactions.
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