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Significance Statement
Spatial resolution of a standard optical microscope is set by the diffraction limit as formulated by Abbe in 1873 to the order of the wavelength of the light. By illuminating an object through a small aperture, a near-field scanning optical microscope (NSOM) enables us to obtain images with spatial resolution unlimited by the diffraction limit. Thus near-field scanning optical microscopes have been widely used to image objects in sub-wavelength scales. An near-field scanning optical microscope, however, has not been used for illumination or collection of circularly polarized light because small tensions or torsions provoke strain-induced birefringence at the near-field scanning optical microscope probe tip. Researchers in University of Tsukuba, Institute of Advanced Industrial Science and Technology and NTT Basic Research Laboratories have successfully developed a circularly polarized near-field scanning optical microscope by fabricating an near-field scanning optical microscope probe tip with an aperture with good axial symmetry and by developing a systematic method to compensate the residual retardation by controlling the polarization of the incident light such that the light emitted from an near-field scanning optical microscope tip to be circularly polarized.
Their newly developed circularly polarized-near-field scanning optical microscope has significantly extended application of near-field scanning optical microscopes to polarimetry including birefringence and circular dichroism. They have demonstrated to optically inject spins locally. They have successfully obtained real-space mappings of spin-resolved quantum Hall chiral edge states near the edge of a GaAs/AlGaAs single heterojunction sample, and have found a clear evidence for the formation of spin-split incompressible strips induced by the exchange energy enhanced spin-gap. Their circularly polarized-near-field scanning optical microscope opens up new opportunities to study spin-related phenomena in a variety of nanostructured materials. Their circularly polarized-near-field scanning optical microscope may also contribute to research and development of spintronics devices and devices based on topological insulator.
Journal Reference
Applied Physics A: Volume 121, Issue 4 (2015), Page 1341-1345
Shintaro Nomura 1, Syuhei Mamyouda 1,Hironori Ito1,Yusuke Shibata 1,Tomoya Ohira 1, Luno Yoshikawa1,Youiti Ootuka 1,Satoshi Kashiwaya 2,Masumi Yamaguchi 3,Hiroyuki Tamura 3,Tatsushi Akazaki 3
[expand title=”Show Affiliations”]- Division of Physics, University of Tsukuba, 1-1-1 Tennoudai, Tsukuba, 305-8571, Japan
- National Institute of Advanced Industrial Science and Technology, 1-1-1 Umezono, Tsukuba, 305-8568, Japan
- NTT Basic Research Laboratories, 3-1 Morinosato-Wakamiya, Atsugi, 243-0198, Japan
Abstract
We report on investigations of the quantum Hall chiral edge states using a near-field scanning optical microscope that enables us to irradiate circularly polarized light from the probe tip with spatial resolution below the diffraction limit. We have found a clear evidence for the formation of spin-split incompressible strips near the edge of a two-dimensional electron system in high magnetic fields.
Go To Applied Physics AFigure Legend
(a) Scanning ion microscope image of an near-field scanning optical microscope probe tip with the size of the aperture of about 100 nm fabricated by focused ion beam slicing of the apex of the tip. (b) Schematics of measurement setup for real-space mappings of spin-resolved quantum Hall chiral edge states near the edge of a GaAs/AlGaAs single heterojunction sample in external magnetic field B.
