Due to its unique layer-number dependent electronic band structure and strong excitonic features, atomically thin MoS is an ideal 2D system where intriguing photoexcited-carrier-induced phenomena can be detected in excitonic luminescence. We perform micro-photoluminescence (PL) measurements and observe that the PL peak redshifts nonlinearly in mono- and bi-layer MoS as the excitation power is increased. The excited carrier-induced optical bandgap shrinkage is found to be proportional to n, where n is the optically-induced free carrier density. The large exponent value of 4/3 is explicitly distinguished from a typical value of 1/3 in various semiconductor quantum well systems. The peculiar n dependent optical bandgap redshift may be due to the interplay between bandgap renormalization and reduced exciton binding energy.
A ferromagnetic/ferroelectric hybrid double quantum disk structure is proposed, capable of manipulating spin states. Switching of spontaneous electric polarization of the ferroelectric quantum disk changes the potential profile of the system and induces ground state transition. Two carrier spin states are separated into ferroelectric semiconductor and diluted magnetic semiconductor disks via asymmetric Zeeman splitting of the coupled quantum disks. The proof of the spin separation resulting from the dipole polarization switching is shown by the probability density change of the lowest energy subband. Evolution of the spin state is also predicted from the subband energy diagram as a function of the bias voltage.
We study the spin miniband structure and the ballistic spin‐polarized transport of a magnetic superlattice (MSL), formed by inhomogeneous magnetic field in a semiconductor nanowire. Based on the transfer matrix theory and Bloch's theorem, we calculate the energy dispersion having spin‐minibands and spin‐minigaps due to Bloch periodicity and spin‐dependent ballistic conductance for various geometrical and physical parameters. Results show that full spin‐polarization in the ballistic conductance of the system occurs clearly for each spin, and that the fully spin‐polarized range for each spin can be enhanced by modulation of geometrical and physical parameters.
Schematic diagram of a MSL constructed by superconducting gridded mask on the top of a quantum wire formed by the split gate technique in two‐dimensional electron gas system. Transverse modes in Q1DEG serve as transmission channels.
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