Materials Physics and Applications DivisionCondensed Matter and Magnet Science, MPA-CMMS

Optical Spectroscopy

Scott Crooker – Capability Leader

Description of Capabilities

Our experiments typically focus on UV-VIS-NIR optical spectroscopy in our high-field magnets. Techniques include standard photoluminescence, reflection, and absorption spectroscopy, as well as Faraday/Kerr rotation, magnetic circular dichroism, time-resolved PL, fluorescence line-narrowing, and ultrafast pump-probe studies. Depending on the experiment, temperatures from 300K down to 300mK are available, in a variety of magnetic fields that include (i) an 8T superconducting split-coil with direct optical access in both Faraday and Voigt geometry, (ii) a 17T superconducting solenoid (access is usually via optical fiber), and (iii) pulsed fields to ~90T (fiber access).

Advanced techniques include scanning Kerr-rotation microscopy, spin noise spectroscopy, terahertz spectroscopy, single-dot magneto-spectroscopy. (See publications below.)

Standard source/detector equipment in the lab includes:

• Coherent 899-05 Ti/Dye Ring laser (pumped by 6W at 532nm)
• Coherent Mira ultrafast Ti:sapphire (100fs pulsewidth, 76 MHz rep rate, with frequency doubler and external pulse-picker)
• Pulsed diode laser at 640nm
• cw laser sources at 325nm, 405nm, 442m, 532, 633nm, 785nm, 1064nm, visible argon-ion lines, various NIR diode lines
• Xe lamp and tungsten blackbody lamp
• Acton 300i, 500i spectrometers
• Princeton Instruments backthinned silicon CCDs (~300-1100nm), also InGaAs diode array (~900-1600nm).
• fast Si avalanche photodiodes

Material systems that we've studied to date include:

• Semiconductors (bulk, quantum wells & 2DEGss, wires, dots) (both magnetic and nonmagnetic) based on GaAs, CdTe, ZnSe, GaN, ZnO
• Carbon nanotubes
• Colloidal semiconductor quantum dots (CdSe, ZnSe, PbSe, Ge)
• Organic semiconductors incorporating metal-porphyrine/phthalocyanine complexes.
• Some correlated-electron materials

Some relevant publications are listed below. Learn more about current research projects.

Tunable magnetic exchange interactions in Mn-doped inverted core-shell ZnSe/CdSe nanocrystals
D. A. Bussian, S. A. Crooker, M. Yin, M. Brynda, Al. L. Efros, and V. I. Klimov
Nature Materials 8, 35 (2009), arXiv.0811.1036v1

Spin noise of electrons and holes in self-assembled (In,Ga)As quantum dots
S. A. Crooker, J. Brandt, C. Sandfort, A. Greilich, D. R. Yakovlev, D. Reuter, A. D. Wieck, and M. Bayer
Physical Review Letters 104, 036601 (2010); arXiv:0909.1592v1

Anomalous circular polarization of magneto-photoluminescence from individual CdSe nanocrystals
H. Htoon, S. A. Crooker, M. Furis, S. Jeong, Al. L. Efros, and V. I. Klimov
Physical Review Letters 102, 017402 (2009). arXiv:0809.1116v1

Bright exciton fine structure and anisotropic exchange in CdSe nanocrystal quantum dots
M. Furis, T. Barrick, M. Petruska, H. Htoon, V. I. Klimov, and S. A. Crooker
Physical Review B Rapid Communications 73, 241313(R) (2006); cond-mat/0511567.

Magneto-optical spectroscopy of highly-aligned carbon nanotubes: Identifying the role of threading magnetic flux
J. Shaver et al.
Physical Review B Rapid Communications 78, 081402(R) (2008).

Imaging Spin Transport in Lateral Ferromagnet/Semiconductor Structures
S. A. Crooker, M. Furis, X. Lou, C. Adelmann, D. L. Smith, C. J. Palmstrom, and P. A. Crowell
Science 309, 2191 (2005).

Definitive observation of the dark triplet ground state of charged excitons in high magnetic fields
G. V. Astakhov et al.
Phys. Rev. B Rapid Communications 71, 201312 (2005); cond-mat/0503693.

Tuning alloy disorder in diluted magnetic semiconductors in high fields to 89 tesla
S. A. Crooker and N. Samarth
Applied Physics Letters 90, 102109 (2007); cond-mat/0612332.

Spectrally-resolved dynamics of energy transfer in quantum dot assemblies: Towards engineered energy flows in artificial materials
S. A. Crooker, J. Hollingsworth, S. Tretiak, and V. I. Klimov
Physical Review Letters 89, 186802 (2002).

Stability of trions in strongly spin-polarized two-dimensional electron gases
S. A. Crooker, E. Johnston-Halperin, D. D. Awschalom, R. Knobel, and N. Samarth
Phys. Rev. B Rapid Communications 61, R16307 (2000).