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 language | English |
|---|---|
| Pages (from-to) | 137-142 |
| Number of pages | 6 |
| Journal | Nature Nanotechnology |
| Volume | 11 |
| Issue number | 2 |
| DOIs | |
| Publication status | Published - Feb 1 2016 |
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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 journal › Article
}
TY - JOUR
T1 - Revealing giant internal magnetic fields due to spin fluctuations in magnetically doped colloidal nanocrystals
AU - Rice, William D.
AU - Liu, Wenyong
AU - Baker, Thomas A.
AU - Sinitsyn, Nikolai A.
AU - Klimov, Victor I
AU - Crooker, Scott A.
PY - 2016/2/1
Y1 - 2016/2/1
N2 - 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.
AB - 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.
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U2 - 10.1038/nnano.2015.258
DO - 10.1038/nnano.2015.258
M3 - Article
VL - 11
SP - 137
EP - 142
JO - Nature Nanotechnology
JF - Nature Nanotechnology
SN - 1748-3387
IS - 2
ER -