Magnetoplasmon Resonances in Semiconductor Nanocrystals: Potential for a New Information Technology Platform

Abstract

Interaction between light and plasmon oscillations in semiconductor nanocrystals has received significant attention in recent years driven, in part, by the possibility of coupling between plasmonic and semiconducting properties. Such coupling could lead to a variety of new applications in plasmonics, photonics, and optoelectronics. In this Concept we discuss the methods for generation of localized surface plasmon resonances in colloidal semiconductor nanocrystals and their unique magneto-optical properties. Different means of introducing free charge carriers, including aliovalent doping, non-stoichiometry, and external charging, are first compared and contrasted. The resulting plasmons can be manipulated using circularly polarized light and external magnetic field, allowing for the formation of the magnetoplasmon modes. The concept of using these magnetoplasmon modes as a new degree of freedom for controlling excitonic states and charge-carrier polarization is introduced and discussed. We also highlight some notable recent examples of controlling plasmon-exciton interactions and comment on their implications for future research in sustainable information technology.

On the Origin of d0 Magnetism in Transparent Metal Oxide Nanocrystals

“…As evident in Figure c, warming up the sample also causes the exciton MCD spectra to broaden and shift to lower energies, following the behavior of the optical absorption spectra (Figure S2). The temperature dependence of the band gap energy arises predominantly from the thermal lattice expansion and electron–phonon coupling, as predicted by Varshni and related models. , The residual temperature-independent signal above 50 K (A-term MCD) has a linear dependence on the magnetic field (Figure S3) and can be associated with an intrinsic exciton g -factor or excitonic splitting due to magnetic field-induced circular/cyclotron motion of free charge carriers, as previously observed in plasmonic metal oxide NCs. − To extract the temperature-dependent component from the measured MCD spectrum at 6 T, we subtract the corresponding 200 K spectrum from the 5 K6 T spectrum in Figure a (inset in Figure a). At 200 K, the spectral broadening and energy position of the excitonic transition remain very similar to those at 5 K, but the integrated intensity reflects only the temperature-independent contribution.…”

Magneto-optical methods for magnetoplasmonics in noble metal nanostructures

“…However, further studies on the correlation between magnetoplasmonic modes and spin polarization of charge carriers can potentially trigger new opportunities both in the field of magnetoplasmonics and spintronics, with potential implications for future applications in information technology. 77…”

Properties of Free Charge Carriers Govern Exciton Polarization in Plasmonic Semiconductor Nanocrystals

“…The degenerately doped colloidal semiconductor nanocrystals (NCs) with broadly tunable localized surface plasmon resonance (LSPR) and inherently semiconducting behavior provide an intriguing platform for probing the interaction between plasmon, charge, and spin. − Using magnetic circular dichroism (MCD) spectroscopy, we have recently demonstrated the exciton polarization in degenerately doped semiconductor metal oxide NCs, enabled by magnetic-field-induced cyclotron oscillations of plasmon-related free electrons. , The degree of exciton polarization has been correlated to the oscillator strength and dephasing of the LSPR in these NCs, suggesting that carrier concentration and scattering directly impact the transfer of angular momentum from the cyclotron electrons to the excitonic states . The plasmonic properties of semiconductor NCs are determined by the type and effective mass of charge carriers according to the Drude–Lorentz model .…”