Related Experiment Video
Updated: May 21, 2026
15:58
Measurement of Coherence Decay in GaMnAs Using Femtosecond Four-wave Mixing
Published on: December 3, 2013
Optically rewritable patterns of nuclear magnetization in gallium arsenide.
Jonathan P King1, Yunpu Li, Carlos A Meriles
1Department of Chemical Engineering, University of California, 201 Gilman Hall, Berkeley, California 94720, USA. jpking@berkeley.edu
Nature Communications
|June 28, 2012
Summary
Researchers can now control nuclear spin polarization patterns in semiconductors using light. This breakthrough enables precise, rewritable polarization for quantum computing and spintronics applications.
Area of Science:
- Materials Science
- Quantum Information Science
- Condensed Matter Physics
Background:
- Nuclear spin polarization is crucial for developing quantum computing and spintronics technologies.
- Precise spatial control over nuclear polarization sign and magnitude is needed for advanced applications.
Purpose of the Study:
- To demonstrate all-optical control and imaging of nuclear spin polarization patterns in bulk semiconductors.
- To investigate the use of light properties and NMR sequences for tailoring polarization.
Main Methods:
- Utilizing optical pumping with controlled light helicity, intensity, and wavelength.
- Exploiting different electron-nuclear interaction mechanisms.
- Employing Nuclear Magnetic Resonance (NMR) pulse sequences for fine-tuning polarization.
Main Results:
- Successfully controlled and imaged the sign of nuclear polarization spatially, as a function of distance from an irradiated GaAs surface.
- Demonstrated all-optical creation of micron-scale, rewritable patterns of positive and negative nuclear polarization.
- Achieved polarization control without ferromagnets, lithography, or quantum-confined structures.
Conclusions:
- This method offers a novel way to engineer nuclear spin polarization in bulk semiconductors.
- The all-optical, rewritable polarization patterns are promising for future spintronic devices and quantum information processing.
More Related Videos
Related Concept Videos
01:05Atomic Nuclei: Magnetic Resonance
The number of nuclear spins aligned in the lower energy state is slightly greater than those in the higher energy state. In the presence of an external magnetic field, as the spins precess at the Larmor frequency, the excess population results in a net magnetization oriented along the z axis. When a pulse or a short burst of radio waves at the Larmor frequency is applied along the x axis, the coupling of frequencies causes resonance and flips the nuclear spins of the excess population from the...
01:23Atomic Nuclei: Nuclear Relaxation Processes
In the absence of an external magnetic field, nuclear spin states are degenerate and randomly oriented. When a magnetic field is applied, the spins begin to precess and orient themselves along (lower energy) or against (higher energy) the direction of the field. At equilibrium, a slight excess population of spins exists in the lower energy state. Because the direction of the magnetic field is fixed as the z-axis, the precessing magnetic moments are randomly oriented around the z-axis. This...
01:03Atomic Nuclei: Nuclear Spin State Overview
NMR-active nuclei have energy levels called 'spin states' that are associated with the orientations of their nuclear magnetic moments. In the absence of a magnetic field, the nuclear magnetic moments are randomly oriented, and the spin states are degenerate. When an external magnetic field is applied, the spin states have only 2 + 1 orientations available to them. A proton with = ½ has two available orientations. Similarly, for a quadrupolar nucleus with a nuclear spin value of one, the...
01:17NMR Spectrometers: Radiofrequency Pulses and Pulse Sequences
A pulse is a short burst of radio waves distributed over a range of frequencies that simultaneously excites all the nuclei in the sample. Upon passing a radio frequency pulse along the x-axis, the nuclei absorb energy corresponding to their Larmor frequencies and achieve resonance. This shifts the net magnetization vector from the z-axis toward the transverse plane. This angle of rotation of the magnetization vector, or the flip angle, is proportional to the duration and intensity of the pulse.
01:22Carrier Generation and Recombination
Carrier generation is the process by which electron-hole pairs (EHPs) are created within the semiconductor. In direct-bandgap semiconductors, such as gallium arsenide (GaAs), this occurs efficiently when energy absorption prompts valence electrons to leap into the conduction band, leaving behind holes.
This process is given by the generation rate G and is efficient due to the conservation of momentum between the valence band maximum and conduction band minimum.
Indirect generation involves an...
This process is given by the generation rate G and is efficient due to the conservation of momentum between the valence band maximum and conduction band minimum.
Indirect generation involves an...