Abstract
We report on an example of confined magnetic ions with long spin coherence near room temperature. This was achieved by confining single Mn2+ spins in colloidal semiconductor quantum dots (QDs) and by dispersing the QDs in a proton-spin free matrix. The controlled suppression of Mn–Mn interactions and minimization of Mn–nuclear spin dipolar interactions result in unprecedentedly long phase memory (TM ~ 8 μs) and spin–lattice relaxation (T1 ~ 10 ms) time constants for Mn2+ ions at T = 4.5 K, and in electron spin coherence observable near room temperature (TM ~ 1 μs).
Highlights
We report on an example of confined magnetic ions with long spin coherence near room temperature
Pulsed electron spin resonance (ESR) studies have enabled the identification of the main sources of electron spin dephasing in magnetic colloidal quantum dots (QDs), i.e. Mn–Mn dipolar interactions and hyperfine interactions of the Mn spins with the protons of the capping ligands[7,19]. These findings indicate that much longer electron spin dynamics and improved control of quantum coherences could be achieved by tailoring the separation between the Mn ions and by reducing Mn–nuclear spin interactions
We examine the effect of the Mn-Mn separation in PbS:Mn QDs diluted in different solvents (Fig. 2a–c) on the phase memory and spin–lattice relaxation time constants of Mn2+ ions at T = 5 K (see Fig. 2(d) and Table 1)
Summary
We report on an example of confined magnetic ions with long spin coherence near room temperature. The interest in Mn-doped QDs has risen due to the observation of Rabi oscillations and quantum coherence with a phase memory time constant TM of the order of a few microseconds at liquid He-temperature[7,18,19,20] These exceed the coherence times previously reported for layered[21], quantum wells[22,23] and self-assembled QDs20,24,25, either doped with Mn ions or confining a single electron, by one order of magnitude or more. This result can be ascribed to the localization of electrons in 3d orbitals, small spin–orbit interactions and minimized nuclear spin bath noise.
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