2 research outputs found
Direct Measurements of Magnetic Polarons in Cd<sub>1–<i>x</i></sub>Mn<sub><i>x</i></sub>Se Nanocrystals from Resonant Photoluminescence
In
semiconductors, quantum confinement can greatly enhance the
interaction between band carriers (electrons and holes) and dopant
atoms. One manifestation of this enhancement is the increased stability
of <i>exciton magnetic polarons</i> in magnetically doped
nanostructures. In the limit of very strong 0D confinement that is
realized in colloidal semiconductor nanocrystals, a single exciton
can exert an effective exchange field <i>B</i><sub>ex</sub> on the embedded magnetic dopants that exceeds several tesla. Here
we use the very sensitive method of resonant photoluminescence (PL)
to directly measure the presence and properties of exciton magnetic
polarons in colloidal Cd<sub>1–<i>x</i></sub>Mn<sub><i>x</i></sub>Se nanocrystals. Despite small Mn<sup>2+</sup> concentrations (<i>x</i> = 0.4–1.6%), large polaron
binding energies up to ∼26 meV are observed at low temperatures
via the substantial Stokes shift between the pump laser and the resonant
PL maximum, indicating nearly complete alignment of all Mn<sup>2+</sup> spins by <i>B</i><sub>ex</sub>. Temperature and magnetic
field-dependent studies reveal that <i>B</i><sub>ex</sub> ≈ 10 T in these nanocrystals, in good agreement with theoretical
estimates. Further, the emission line widths provide direct insight
into the statistical fluctuations of the Mn<sup>2+</sup> spins. These
resonant PL studies provide detailed insight into collective magnetic
phenomena, especially in lightly doped nanocrystals where conventional
techniques such as nonresonant PL or time-resolved PL provide ambiguous
results
Supplement 1: Acousto-optical nanoscopy of buried photonic nanostructures
Supplemental Content Originally published in Optica on 20 June 2017 (optica-4-6-588