Revealing giant internal magnetic fields due to spin fluctuations in magnetically doped colloidal nanocrystals

William D. Rice, Wenyong Liu, Thomas A. Baker, Nikolai A. Sinitsyn, Victor I Klimov, Scott A. Crooker

Research output: Contribution to journalArticle

23 Citations (Scopus)

Abstract

Strong quantum confinement in semiconductors can compress the wavefunctions of band electrons and holes to nanometre-scale volumes, significantly enhancing interactions between themselves and individual dopants. In magnetically doped semiconductors, where paramagnetic dopants (such as Mn 2+, Co 2+ and so on) couple to band carriers via strong sp-d spin exchange, giant magneto-optical effects can therefore be realized in confined geometries using few or even single impurity spins. Importantly, however, thermodynamic spin fluctuations become increasingly relevant in this few-spin limit. In nanoscale volumes, the statistical fluctuations of N spins are expected to generate giant effective magnetic fields B eff, which should dramatically impact carrier spin dynamics, even in the absence of any applied field. Here we directly and unambiguously reveal the large B eff that exist in Mn 2+ -doped CdSe colloidal nanocrystals using ultrafast optical spectroscopy. At zero applied magnetic field, extremely rapid (300-600â €...GHz) spin precession of photoinjected electrons is observed, indicating B eff â 1/4 15 â '30 T for electrons. Precession frequencies exceed 2 THz in applied magnetic fields. These signals arise from electron precession about the random fields due to statistically incomplete cancellation of the embedded Mn 2+ moments, thereby revealing the initial coherent dynamics of magnetic polaron formation, and highlighting the importance of magnetization fluctuations on carrier spin dynamics in nanomaterials.

Original languageEnglish
Pages (from-to)137-142
Number of pages6
JournalNature Nanotechnology
Volume11
Issue number2
DOIs
Publication statusPublished - Feb 1 2016

Fingerprint

Spin fluctuations
Nanocrystals
nanocrystals
Magnetic fields
Spin dynamics
precession
Electrons
magnetic fields
spin dynamics
Doping (additives)
Semiconductor materials
electrons
Gene Conversion
Magnetooptical effects
Quantum confinement
Wave functions
Nanostructured materials
spin exchange
Magnetization
cancellation

ASJC Scopus subject areas

  • Bioengineering
  • Biomedical Engineering
  • Materials Science(all)
  • Electrical and Electronic Engineering
  • Condensed Matter Physics
  • Atomic and Molecular Physics, and Optics

Cite this

Revealing giant internal magnetic fields due to spin fluctuations in magnetically doped colloidal nanocrystals. / Rice, William D.; Liu, Wenyong; Baker, Thomas A.; Sinitsyn, Nikolai A.; Klimov, Victor I; Crooker, Scott A.

In: Nature Nanotechnology, Vol. 11, No. 2, 01.02.2016, p. 137-142.

Research output: Contribution to journalArticle

Rice, William D. ; Liu, Wenyong ; Baker, Thomas A. ; Sinitsyn, Nikolai A. ; Klimov, Victor I ; Crooker, Scott A. / Revealing giant internal magnetic fields due to spin fluctuations in magnetically doped colloidal nanocrystals. In: Nature Nanotechnology. 2016 ; Vol. 11, No. 2. pp. 137-142.
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