Charge fluctuations of a Cr atom probed in the optical spectra of a quantum dot

Besombes, L.; Boukari, H.; Tiwari, Vivekanand; Lafuente-Sampietro, Alban; Sunaga, M.; Makita, Kenji; Kuroda, Shinji

doi:10.1103/physrevb.99.035309

Cited by 5 publications

(6 citation statements)

References 30 publications

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“…The studied sample consists of a layer of Cr-doped selfassembled CdTe QDs grown by molecular beam epitaxy on a p-doped ZnTe (001) substrate 11,24 . A low density of Cr in the CdTe layer is chosen to avoid multiple Cr inside 19 or in the vicinity 12 of the dots to interact with the carriers confined in a given QD.…”

Section: Introductionmentioning

confidence: 99%

Influence of nonequilibrium phonons on the spin dynamics of a single Cr atom

et al. 2020

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We analyse the influence of optically generated non-equilibrium phonons on the spin relaxation and effective spin temperature of an individual Cr atom inserted in a quantum dot. Using a three pulses pump-probe technique, we show that the spin relaxation measured in resonant optical pumping experiments strongly depends on the optical excitation conditions. We observe for an isolated Cr in the dark a heating time shorter than a few hundreds ns after an initial high power non-resonant excitation pulse. A cooling time larger than a few tens of µs, independent on the excitation, is obtained in the same experimental conditions. We show that a tunable spin-lattice coupling dependent on the density of non-equilibrium phonons can explain the observed dynamics. Low energy excitation conditions are found where the Cr spin states Sz=±1 can be efficiently populated by a non-resonant optical excitation, prepared and read-out by resonant optical pumping and conserved in the dark during a few µs. arXiv:1911.07639v1 [cond-mat.mes-hall]

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Section: Introductionmentioning

confidence: 99%

Influence of nonequilibrium phonons on the spin dynamics of a single Cr atom

et al. 2020

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“…Let us also note that fluctuations of Cr charge states have been observed for Cr atoms located in the ZnTe barriers in the vicinity of the dots 8 . In this case, the exchange interaction with holes in the bulk is weak and parallel spin configuration is not stabilized.…”

Section: The Charge States Of Cr In Cdtementioning

confidence: 91%

“…A single magnetic atom can also present a large magnetic anisotropy and a spin memory when interacting with ligands in a molecular magnet 2 . In semiconductors, the optical properties of a quantum dot (QD) can be used to control the spin of individual magnetic atoms 3,4,[6][7][8][9][10]10 . Embedding a magnetic atom in a QD offers in addition the possibility to tune the environment of the localized spin.…”

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A hole-Cr$^{+}$ nano-magnet in a semiconductor quantum dot

Tiwari,

Arino,

Gupta

et al. 2021

Preprint

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We study a new diluted magnetic semiconductor system based on the spin of the ionized acceptor Cr + . We show that the negatively charged Cr + ion, an excited state of the Cr in II-VI semiconductor, can be stable when inserted in a CdTe quantum dot (QD). The Cr + attracts a heavy-hole in the QD and form a stable hole-Cr + complex. Optical probing of this system reveals a ferromagnetic coupling between heavy-holes and Cr + spins. At low temperature, the thermalization on the ground state of the hole-Cr + system with parallel spins prevents the optical recombination of the excess electron on the 3d shell of the atom. We study the dynamics of the nano-magnet formed by the hole-Cr + exchange interaction. The ferromagnetic ground states with Mz=±4 can be controlled by resonant optical pumping and a spin relaxation time in the 20 µs range is obtained at T=4.2 K. This spin memory at zero magnetic field is limited by the interaction with phonons.

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“…As we show, the simple picture is invalidated by the interplay between optical orientation of the exciton and the non-trivial dependence of the TM ion spin on the selection rules in anisotropic quantum dots. Our considerations will be showcased using a particular system of a CdSe/ZnSe QD with single Fe 2+ ion [14], but the same reasoning should be valid also for all other known systems of that kind [20][21][22].…”

Section: Introductionmentioning

confidence: 92%

Readout of a dopant spin in the anisotropic quantum dot with a single magnetic ion

Rodek

Kazimierczuk

Bogucki

et al. 2019

J. Phys.: Condens. Matter

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Owing to exchange interaction between the exciton and magnetic ion, a quantum dot embedding a single magnetic ion is a great platform for optical control of individual spin. In particular, a quantum dot provides strong and sharp optical transitions, which give experimental access to spin states of an individual magnetic ion. We show, however, that physics of quantum dot excitons also complicate spin readout and optical spin manipulation in such a system. This is due to electron-hole exchange interaction in anisotropic quantum dots, which affects the polarization of the emission lines. One of the consequences is that the intensity of spectral lines in a single spectrum are not simply proportional to the population of various spin states of magnetic ion. In order to provide a solution of the above problem, we present a method of extracting both the spin polarisation degree of a neutral exciton and magnetic dopant inside a semiconductor quantum dot in an external magnetic field. Our approach is experimentally verified on a system of CdSe/ZnSe quantum dot containing a single Fe 2+ ion. Both the resonant and non-resonant excitation regimes are explored resulting in a record high optical orientation efficiency of dopant spin in the former case. The proposed solutions can be easily expanded to any other system of quantum dots containing magnetic dopants.

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Charge fluctuations of a Cr atom probed in the optical spectra of a quantum dot

Cited by 5 publications

References 30 publications

Influence of nonequilibrium phonons on the spin dynamics of a single Cr atom

Influence of nonequilibrium phonons on the spin dynamics of a single Cr atom

A hole-Cr$^{+}$ nano-magnet in a semiconductor quantum dot

Readout of a dopant spin in the anisotropic quantum dot with a single magnetic ion

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