Probing the spin state of a single magnetic ion in an individual quantum dot.
TL;DR: In this paper, the fine structure of a confined exciton in the exchange field of a single Mn2+ ion (S=5/2) was analyzed in detail, and six emission lines were observed at zero magnetic field.
Abstract: The magnetic state of a single magnetic ion (Mn2+) embedded in an individual quantum dot is optically probed using microspectroscopy. The fine structure of a confined exciton in the exchange field of a single Mn2+ ion (S=5/2) is analyzed in detail. The exciton-Mn2+ exchange interaction shifts the energy of the exciton depending on the Mn2+ spin component and six emission lines are observed at zero magnetic field. Magneto-optic measurements reveal that the emission intensities in both circular polarizations are controlled by the Mn2+ spin distribution imposed by the exchange interaction with the exciton, the magnetic field, and an effective manganese temperature which depends on both the lattice temperature and the density of photocreated carriers. Under magnetic field, the electron-Mn interaction induces a mixing of the bright and dark exciton states.
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TL;DR: Progress has been made towards full control of the quantum states of single and coupled spins in a variety of semiconductors and nanostructures, and towards understanding the mechanisms through which spins lose coherence in these systems.
Abstract: During the past few years, researchers have gained unprecedented control over spins in the solid state. What was considered almost impossible a decade ago, in both conceptual and practical terms, is now a reality: single spins can be isolated, initialized, coherently manipulated and read out using both electrical and optical techniques. Progress has been made towards full control of the quantum states of single and coupled spins in a variety of semiconductors and nanostructures, and towards understanding the mechanisms through which spins lose coherence in these systems. These abilities will allow pioneering investigations of fundamental quantum-mechanical processes and provide pathways towards applications in quantum information processing.
473 citations
TL;DR: The huge advances in the past decade towards observing, controllably creating and manipulating single dopants, as well as their application in novel devices which allow opening the new field of solotronics (solitary dopant optoelectronics).
Abstract: The sensitive dependence of a semiconductor's electronic, optical and magnetic properties on dopants has provided an extensive range of tunable phenomena to explore and apply to devices. Recently it has become possible to move past the tunable properties of an ensemble of dopants to identify the effects of a solitary dopant on commercial device performance as well as locally on the fundamental properties of a semiconductor. New applications that require the discrete character of a single dopant, such as single-spin devices in the area of quantum information or single-dopant transistors, demand a further focus on the properties of a specific dopant. This article describes the huge advances in the past decade towards observing, controllably creating and manipulating single dopants, as well as their application in novel devices which allow opening the new field of solotronics (solitary dopant optoelectronics).
381 citations
TL;DR: In this article, the authors provide an overview of efforts to dope one of the most widely studied colloidal semiconductor nanocrystal systems, CdSe quantum dots, with a transition-metal dopant ion, Mn 2+, and describe the major new physical properties that have emerged following successful synthesis of this material.
Abstract: Recent advances in the chemistry of colloidal semiconductor nanocrystal doping have led to new materials showing fascinating physical properties of potential technological importance. This article provides an overview of efforts to dope one of the most widely studied colloidal semiconductor nanocrystal systems, CdSe quantum dots, with one of the most widely studied transition-metal dopant ions, Mn 2+ , and describes the major new physical properties that have emerged following successful synthesis of this material. These properties include spin-polarizable excitonic photoluminescence, magnetic circular dichroism, exciton storage, and excitonic magnetic polaron formation. A brief survey of parallel advances in the characterization of analogous self-assembled Mn 2+ -doped quantum dots grown by molecular beam epitaxy is also presented, and the physical properties of the colloidal quantum dots are shown to compare favorably with those of the self-assembled quantum dots. The rich variety of physical properties displayed by colloidal Mn 2+ -doped CdSe quantum dots highlights the attractiveness of this material for future fundamental and applied research.
378 citations
TL;DR: In this article, the authors demonstrate a widely tunable magnetic sp-d exchange interaction between electron-hole excitations (excitons) and paramagnetic manganese ions using "inverted" core-shell nanocrystals composed of Mn(2+)-doped ZnSe cores overcoated with undoped shells of narrower-gap CdSe.
Abstract: Magnetic doping of semiconductor nanostructures is actively pursued for applications in magnetic memory and spin-based electronics. Central to these efforts is a drive to control the interaction strength between carriers (electrons and holes) and the embedded magnetic atoms. In this respect, colloidal nanocrystal heterostructures provide great flexibility through growth-controlled 'engineering' of electron and hole wavefunctions in individual nanocrystals. Here, we demonstrate a widely tunable magnetic sp-d exchange interaction between electron-hole excitations (excitons) and paramagnetic manganese ions using 'inverted' core-shell nanocrystals composed of Mn(2+)-doped ZnSe cores overcoated with undoped shells of narrower-gap CdSe. Magnetic circular dichroism studies reveal giant Zeeman spin splittings of the band-edge exciton that, surprisingly, are tunable in both magnitude and sign. Effective exciton g-factors are controllably tuned from -200 to +30 solely by increasing the CdSe shell thickness, demonstrating that strong quantum confinement and wavefunction engineering in heterostructured nanocrystal materials can be used to manipulate carrier-Mn(2+) wavefunction overlap and the sp-d exchange parameters themselves.
204 citations
TL;DR: Doped nanocrystals with proper selections of dopant-host pairs may be helpful for generating designer materials for a wide range of current technological needs.
Abstract: Introducing a few atoms of impurities or dopants in semiconductor nanocrystals can drastically alter the existing properties or even introduce new properties For example, mid-gap states created by doping tremendously affect photocatalytic activities and surface controlled redox reactions, generate new emission centers, show thermometric optical switching, make FRET donors by enhancing the excited state lifetime, and also create localized surface plasmon resonance induced low energy absorption In addition, researchers have more recently started focusing their attention on doped nanocrystals as an important and alternative material for solar energy conversion to meet the current demand for renewable energy Moreover, the electrical and magnetic properties of the host are also strongly altered on doping These beneficial dopant-induced changes suggest that doped nanocrystals with proper selections of dopant-host pairs may be helpful for generating designer materials for a wide range of current technological needs How properties relate to the doping of a variety of semiconductor nanocrystals are summarized in this Review
195 citations