Diluted magnetic semiconductor quantum dots: An extreme sensitivity of the hole Zeeman splitting on the aspect ratio of the confining potential

Kyrychenko, F. V.; Kossut, J.

doi:10.1103/physrevb.70.205317

Cited by 39 publications

(36 citation statements)

References 13 publications

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“…In contrast, strong spin orbit interaction of the valence band makes the Mn-hole interaction strongly anisotropic [9,12,16] and it varies between different dot levels. Following previous work [9,15,16], confinement is described by a hard wall cubic potential with L z < L x ' L y . Although real dots are not cubic, this simple model [9,16] provides an excellent description of the Hamiltonian of the Mn spin coupled to the carriers, which is able to account for the nontrivial single-exciton photoluminescence (PL) spectra both for neutral [6 -8] and charged [12] single-Mn-doped CdTe QD.…”

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confidence: 99%

“…In the case of conduction band we neglect spin orbit interactions so that S ; 0 is rotationally invariant [15]. In contrast, strong spin orbit interaction of the valence band makes the Mn-hole interaction strongly anisotropic [9,12,16] and it varies between different dot levels. Following previous work [9,15,16], confinement is described by a hard wall cubic potential with L z < L x ' L y .…”

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confidence: 99%

“…Following previous work [9,15,16], confinement is described by a hard wall cubic potential with L z < L x ' L y . Although real dots are not cubic, this simple model [9,16] provides an excellent description of the Hamiltonian of the Mn spin coupled to the carriers, which is able to account for the nontrivial single-exciton photoluminescence (PL) spectra both for neutral [6 -8] and charged [12] single-Mn-doped CdTe QD. Coulomb repulsion between carriers is described within the constant interaction model:…”

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confidence: 99%

“…QD carriers occupy localized spin orbitals with energy which are described in the envelope functionk p approach [9,15,16]. In the case of valence band holes the 6 band KohnLuttinger Hamiltonian, including spin orbit interaction, is used as a starting point to build the quantum dot states [16]. The Hamiltonian of the isolated dot reads…”

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confidence: 99%

“…In analogy with the standard model [14] for bulk DMS, H QD describes confined conduction-band electrons and valence holes interacting with a localized Mn spin S 5 2 , denoted asM, via a local exchange interaction. QD carriers occupy localized spin orbitals with energy which are described in the envelope functionk p approach [9,15,16]. In the case of valence band holes the 6 band KohnLuttinger Hamiltonian, including spin orbit interaction, is used as a starting point to build the quantum dot states [16].…”

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Single-Electron Transport in Electrically Tunable Nanomagnets

2007

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We study a single-electron transistor (SET) based upon a II-VI semiconductor quantum dot doped with a single-Mn ion. We present evidence that this system behaves like a quantum nanomagnet whose total spin and magnetic anisotropy depend dramatically both on the number of carriers and their orbital nature. Thereby, the magnetic properties of the nanomagnet can be controlled electrically. Conversely, the electrical properties of this SET depend on the quantum state of the Mn spin, giving rise to spindependent charging energies and hysteresis in the Coulomb blockade oscillations of the linear conductance. DOI: 10.1103/PhysRevLett.98.106805 PACS numbers: 73.23.Hk, 78.55.Et, 78.67.Hc, 85.75.ÿd Nanomagnets attract interest both because of their intriguing behavior as relatively macroscopic quantum objects and their potential technological applications as magnetic bits [1] and qbits [2]. The two fundamental properties of a nanomagnet are the net spin of its ground state, S and its magnetic energy anisotropy tensor, K that governs the stability of the magnetization with respect to quantum and thermal fluctuations. Although recent experiments show that single-molecule magnets like Mn 12 [3,4] or metallic Co [5] nanoparticles can be probed in singlemolecule transistor measurements, their properties can hardly be tuned once they are fabricated. Here we show that a single-electron transistor (SET) consisting of a II-VI quantum dot doped with a single-Mn atom behaves like a tunable nanomagnet whose magnetization and anisotropy axis can be reversibly manipulated electrically. Conversely, the conductance and charging energy of the tunable nanomagnet depend on the quantum state of the Mn spin and are not uniquely determined by the gate and the bias voltage.Our proposal is based on two independent progress in nanofabrication. On one side, the fabrication and optical probing of single CdTe quantum dots doped with a singleMn atom [6 -8]. In the absence of carriers, the spin S 5=2 of the Mn is free. Optical excitation of electron-hole pairs into the dot shows that the Mn spin is exchange coupled to both the electron and the hole [6 -9]. On the other side, the control of the charge state of II-VI semiconductor quantum dots with single-electron accuracy has been experimentally demonstrated [10,11] as well as in the case of single-Mn-doped quantum dots [12] and Mn-doped GaAs islands [13].Hamiltonian.-We consider a CdTe quantum dot (QD) doped with a single-Mn, weakly coupled to two metallic and nonmagnetic electrodes. The dot can be gated so that either the valence band or the conduction band is in resonance with the metallic reservoir and the number of either electrons or holes is varied at will. The total Hamiltonian readsHere H QD is the Hamiltonian for the diluted magnetic semiconductor (DMS) quantum dot. In analogy with the standard model [14] for bulk DMS, H QD describes confined conduction-band electrons and valence holes interacting with a localized Mn spin S 5 2 , denoted asM, via a local exchange interaction. QD carriers o...

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Single-Electron Transport in Electrically Tunable Nanomagnets

2007

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Control of single spins in individual magnetic quantum dots

Mariette¹,

Besombes²,

Bougerol³

et al. 2006

Physica Status Solidi (b)

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The optical properties of individual quantum dots doped with a single Mn atom and charged with a single carrier (electron or hole) are analyzed. Bias controlled single-carrier charging combined with photo depletion is used to control the charge state of individual Mn-doped quantum dots. The emission of the neutral, negatively charged and positively charged excitons coupled with a single magnetic atom are observed in the same quantum dot. The emission pattern of the charged excitons differs strongly from that of the neutral excitons (single and biexciton). This difference reflects the fact that the Mn spin is very sensitive to the number of electrons and holes in both the excited and the ground states of the optical transitions. The spectrum of charged excitons in interaction with the Mn atom shows a rich pattern that can be attributed to a strong anisotropy of the hole -Mn exchange interaction This opens the way of storing information on a single carrier spin on a long time scale in the absence of external magnetic field.

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Spin properties of charged single Mn‐doped quantum dots

Léger¹,

Besombes²,

Maingault³

et al. 2006

Physica Status Solidi (b)

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The optical properties of individual quantum dots doped with a single Mn atom and charged with a single carrier (electron or hole) are analyzed. The emission of the neutral, positively charged and negatively charged excitons coupled with a single magnetic atom are observed in the same quantum dot. The spectrum of the charged excitons in interaction with the Mn atom shows a rich pattern attributed to a strong anisotropy of the hole -Mn exchange interaction slightly perturbed by a small valence band mixing. For the positively charged exciton, the emission pattern shows that the different spin states of the hole -Mn complex remain split in the final state after the exciton recombination. This opens the possibility of storing information on a single carrier spin on a long time scale in the absence of external magnetic field.Precise control of electronic spins in semiconductors should lead to the development of novel electronic systems based on the carriers' spin degree of freedom. Magnetic semiconductor quantum dots (QDs), where carriers can strongly interact with the magnetic atoms, hold particular promise as building blocks for such spin-based systems. They have been proposed as single-spin filters or single spin aligners in quantum information processing devices [1,2]. Developing such devices requires, however, the ability to detect and manipulate individual spins. QDs based on II-VI semiconductor compounds offer the unique possibility of tuning independently the incorporation of charge carriers and the magnetic doping. Manganese is indeed introduced into the crystal matrix as an isoelectronic substitution of the II element, with 3d 5 electronic configuration (S = 5/2). This provides a way to study precisely the interaction between injected carriers and the localized magnetic ions. Recently, CdTe/ZnTe QDs doped with single manganese atoms were realized, making it possible to detect optically the quantum states of a single spin S = 5/2 [3].In this work we present the emission features of charged QDs doped with a single Mn atom. These QDs are the unique system allowing to probe the interaction between an individual magnetic atom and a single confined electron or hole. A photo-depletion mechanism is used to control the charge state of individual Mn-doped QDs. The experimental survey of the neutral exciton X (1 electron (e) and 1 hole (h)) and charged excitons X -(2e, 1h) and X + (1e, 2h) shows that the Mn spin is very sensitive to the number of electrons and holes in both the excited and the ground state of the dot [4,5]. Measurements prove that even if a high anisotropy of the (h, Mn) complex is conserved along the growth axis, heavylight hole mixing induced by inhomogeneous relaxation of strains have important effects on its energy structure.

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Diluted magnetic semiconductor quantum dots: An extreme sensitivity of the hole Zeeman splitting on the aspect ratio of the confining potential

Cited by 39 publications

References 13 publications

Single-Electron Transport in Electrically Tunable Nanomagnets

Single-Electron Transport in Electrically Tunable Nanomagnets

Control of single spins in individual magnetic quantum dots

Spin properties of charged single Mn‐doped quantum dots

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