S. A. Crooker

Los Alamos National Laboratory

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Victor I. Klimov

Los Alamos National Laboratory

N. Samarth

Pennsylvania State University

D. R. Yakovlev

TU Dortmund University

Madalina Furis

University of Oklahoma

D. L. Smith

Baylor College of Medicine

Junichiro Kono

Rice University

D. D. Awschalom

Argonne National Laboratory

Andreas V. Stier

Schott (Germany)

Nikolai A. Sinitsyn

Los Alamos National Laboratory

M. Goryca

University of Warsaw

Cooperative Institutions

Los Alamos National Laboratory

179

National High Magnetic Field Laboratory

Centre National de la Recherche Scientifique

Center for Integrated Nanotechnologies

Chinese Academy of Sciences

Rice University

University of California, Santa Barbara

University at Buffalo, State University of New York

Cornell University

Lawrence Berkeley National Laboratory

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Magneto-Optical Properties of CuInS₂ Nanocrystals

The Journal of Physical Chemistry Letters (2014)

William Rice Hunter McDaniel Victor I. Klimov S. A. Crooker

We compare the absorption, photoluminescence, and magneto-optical properties of colloidal CuInS2 (CIS) nanocrystals with two closely related and well-understood binary analogs: Cu-doped ZnSe nanocrystals and CdSe nanocrystals. In contrast with conventional CdSe, both CIS and Cu-doped ZnSe nanocrystals exhibit a substantial energy separation between emission and absorption peaks (Stokes shift) and a marked asymmetry in the polarization-resolved low-temperature magneto-photoluminescence, both of which point to the role of localized dopant/defect states in the forbidden gap. Surprisingly, we find evidence in CIS nanocrystals of spin-exchange coupling between paramagnetic moments in the nanocrystal and the conduction/valence bands of the host lattice, a behavior also observed in Cu-doped ZnSe nanocrystals, where the copper atoms incorporate as paramagnetic Cu2+ ions.

10.1021/jz502154m

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Citations (71)

Tunable magnetic exchange interactions in manganese-doped inverted core-shell ZnSe-CdSe nanocrystals

Bulletin of the American Physical Society (2009)

David Bussian S. A. Crooker Ming Yin M. Brynda Alexander L. Efros

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.

Exchange interaction

Magnetic semiconductor

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Optical studies of 2DEGs in ZnSe quantum wells in high magnetic fields.

OSTI OAI (U.S. Department of Energy Office of Scientific and Technical Information) (2002)

W. Ossau G. V. Astakhov D. R. Yakovlev S. A. Crooker A. Waag

Optical properties of a two-dimensional electron gas in ZnSe/(Zn,Be,Mg)Se quantum well structures have been examined by means of photoluminescence and reflectivity techniques in external magnetic fields up to 50 T. For these structures the Fermi energy of the two-dimensional electron gas is falling in the range between the trion binding energy and the exciton binding energy, which keeps the dominating role of Coulombic interaction between electrons and photoexcited holes. Characteristic peculiarities of optical spectra are discussed.

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Spin noise spectroscopy to probe quantum states of ultracold fermionic atom gases

Bulletin of the American Physical Society (2006)

Bogdan Mihaila S. A. Crooker Krastan B. Blagoev D.G. Rickel P. B. Littlewood

Bogdan Mihaila, Scott A. Crooker, Krastan B. Blagoev, Dwight G. Rickel, Peter B. Littlewood, and Darryl L. Smith Theoretical Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA National High Magnetic Field Laboratory, Los Alamos National Laboratory, Los Alamos, New Mexico 87545, USA Cavendish Laboratory, Madingley Road, Cambridge CB3 0HE, United Kingdom Received 2 March 2006; published 7 December 2006

National laboratory

Ultracold atom

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Strongly bound excitons in Ruddlesden-Popper 2D perovskites

HAL (Le Centre pour la Communication Scientifique Directe) (2018)

Jean‐Christophe Blancon Andreas V. Stier Hsinhan Tsai Wanyi Nie Constantinos C. Stoumpos

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Optical and electrical spin injection and spin transport in hybrid Fe/GaAs devices

Journal of Applied Physics (2007)

S. A. Crooker Madalina Furis X. Lou P. A. Crowell D. L. Smith

We discuss methods for imaging the nonequilibrium spin polarization of electrons in Fe/GaAs spin transport devices. Both optically- and electrically-injected spin distributions are studied by scanning magneto-optical Kerr rotation microscopy. Related methods are used to demonstrate electrical spin detection of optically-injected spin polarized currents. Dynamical properties of spin transport are inferred from studies based on the Hanle effect, and the influence of strain on spin transport data in these devices is discussed.

Hanle effect

Spinplasmonics

Spin pumping

10.1063/1.2722785

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Intrinsic Spin Fluctuations Reveal the Dynamical Response Function of Holes Coupled to Nuclear Spin Baths in (In,Ga)As Quantum Dots

Physical Review Letters (2012)

Yan Li Nikolai A. Sinitsyn D. L. Smith D. Reuter Andreas D. Wieck

The problem of how single "central" spins interact with a nuclear spin bath is essential for understanding decoherence and relaxation in many quantum systems, yet is highly nontrivial owing to the many-body couplings involved. Different models yield widely varying timescales and dynamical responses (exponential, power-law, Gaussian, etc). Here we detect the small random fluctuations of central spins in thermal equilibrium (holes in singly-charged (In,Ga)As quantum dots) to reveal the timescales and functional form of bath-induced spin relaxation. This spin noise indicates long (400 ns) spin correlation times at zero magnetic field, that increase to $\sim$5 $\mu$s as hole-nuclear coupling is suppressed with small (100 G) applied fields. Concomitantly, the noise lineshape evolves from Lorentzian to power-law, indicating a crossover from exponential to inverse-log dynamics.

10.1103/physrevlett.108.186603

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Optical property and Stokes’ shift of Zn1−xCdxO thin films depending on Cd content

Journal of Applied Physics (2006)

Hong Seong Kang Jae Won Kim Jong Hoon Kim Sang Yeol Lee Ying Li

Ternary Zn1−xCdxO films were grown on (0001) sapphire substrates by pulsed laser deposition. The energy band gap of Zn1−xCdxO films decreases with increasing Cd content. An increase of Cd content also leads to the emission broadening, absorption edge broadening, and crystallinity degradation. The absorption edge and ultraviolet emission energy shift to lower energy from 3.357eVto3.295eV and 3.338eVto3.157eV, respectively, with increasing Cd content from 0.3% to 3% at 4K. The Stokes’ shift between the absorption and emission is observed and that indicates the increase of exciton localization with Cd content.

Stokes shift

Absorption edge

Pulsed Laser Deposition

Ultraviolet

10.1063/1.2186372

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Citations (60)

Electrons, holes, and excitons in monolayer semiconductors: Magneto-optical studies of polarization dynamics and dielectric screening

Bulletin of the American Physical Society (2017)

S. A. Crooker

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Six-Body and Eight-Body Exciton States in Monolayer WSe2

Physical Review Letters (2022)

Dinh Van Tuan Su‐Fei Shi Xiaodong Xu S. A. Crooker Hanan Dery

In the archetypal monolayer semiconductor WSe_{2}, the distinct ordering of spin-polarized valleys (low-energy pockets) in the conduction band allows for studies of not only simple neutral excitons and charged excitons (i.e., trions), but also more complex many-body states that are predicted at higher electron densities. We discuss magneto-optical measurements of electron-rich WSe_{2} monolayers and interpret the spectral lines that emerge at high electron doping as optical transitions of six-body exciton states ("hexcitons") and eight-body exciton states ("oxcitons"). These many-body states emerge when a photoexcited electron-hole pair interacts simultaneously with multiple Fermi seas, each having distinguishable spin and valley quantum numbers. In addition, we explain the relations between dark trions and satellite optical transitions of hexcitons in the photoluminescence spectrum.

Trion

10.1103/physrevlett.129.076801

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Citations (32)