Spin manipulation and spin-lattice interaction in magnetic colloidal quantum dots

Abstract

We report on the spin-lattice interaction and coherent manipulation of electron spins in Mn-doped colloidal PbS quantum dots (QDs) by electron spin resonance. We show that the phase memory time,TM, is limited by Mn-Mn dipolar interactions, hyperfine interactions of the protons (H1) on the QD capping ligands with Mn ions in their proximity (<1 nm), and surface phonons originating from thermal fluctuations of the capping ligands. In the low Mn concentration limit and at low temperature, we achieve a long phase memory time constant TM�0.9μs, thus enabling the observation of Rabi oscillations. Our findings suggest routes to the rational design of magnetic colloidal QDs with phase memory times exceeding the current limits of relevance for the implementation of QDs as qubits in quantum information processing. © Published by the American Physical Society

Electron spin coherence near room temperature in magnetic quantum dots

“…The latter implies reduced electron spin – lattice interactions, leading to a relatively long electron spin–lattice relaxation time constant ( T 1 ) 15 , as well as to an efficient energy transfer between Mn spins and confined quantum carriers mediated by sp–d interactions 16 17 . Recently, the interest in Mn-doped QDs has risen due to the observation of Rabi oscillations and quantum coherence with a phase memory time constant T M 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 QDs 20 24 25 , either doped with Mn ions or confining a single electron, by one order of magnitude or more.…”

“…Pulsed electron spin resonance (ESR) studies have enabled the identification of the main sources of electron spin dephasing in magnetic colloidal 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.…”

Developing Mn-doped lead sulfide quantum dots for MRI labels

“…31 Self-purification mechanisms 4 can lead to impurity out-diffusion resulting in greater impurity content in the proximity of the QD surface compared to the centre. 32 The greater Mn-dependent reduction of T 1 and T 2 times at low Mn compared to higher Mn content indicates a saturation of the concentration of Mn-ions close to the QD surface. Representative T 1 and T 2 times of serial dilution of (PbMn)S QDs with 4.5% and corresponding T 2 -weighted images are shown in Fig.…”

Atomic and electronic structure of CdS-based quantum dots

“…There is extensive research for the application of quantum dots having magnetic properties [3,4]. Quantum dots are also promising materials for new generation photovoltaics [5,6]. A major part of the unique physicochemical properties of new quantum nanostructures depend on their local atomic ordering and electronic structure.…”