Formation of edge state and optical Tamm state inside crystalline specimen using spatial phase modulation of X-ray beam

2022 Fiscal Year Final Research Report

• Project/Area Number: 20K03824
• Research Category: Grant-in-Aid for Scientific Research (C)
• Allocation Type: Multi-year Fund
• Section: 一般
• Review Section: Basic Section 13020:Semiconductors, optical properties of condensed matter and atomic physics-related
• Research Institution: Institute of Physical and Chemical Research
• Principal Investigator: Kohmura Yoshiki 国立研究開発法人理化学研究所, 放射光科学研究センター, チームリーダー (30270599)
• Co-Investigator(Kenkyū-buntansha): 澤田 桂 国立研究開発法人理化学研究所, 放射光科学研究センター, 研究員 (40462692) ; 大和田 謙二 国立研究開発法人量子科学技術研究開発機構, 関西光科学研究所 放射光科学研究センター, グループリーダー (60343935)
• Project Period (FY): 2020-04-01 – 2023-03-31
• Keywords: X線 / 局在状態生成 / トポロジー / 横滑り現象

Outline of Final Research Achievements

X-ray localization could occur at a lattice with its spacing modulated from other area which equivalently broke the gap of the dispersion curve of perfect crystals, in a similar manner as in band topology of nano-photonics. We used the void- or inclusion-type of stacking faults on (111) diamond crystal plane where either one third of lattice spacing is reduced or enlarged compared to normal unit cell. It was important to spatially separate the weak effect of X-ray localization from X-ray transmission through crystal which was realized by X-ray translation effect, where deflection of X-ray trajectory occurred at deformed lattice planes. Our theoretical research showed the potential of X-ray localization in the proximity of interface. We, however, found that X-ray propagation was dominated by other propagation mode, which was visualized by two-wave interference fringes due to the allowed two wave vectors inside crystal after the termination of X-ray translation effect at interface

Free Research Field

X線光学

Academic Significance and Societal Importance of the Research Achievements

電磁波の反射に適した周期長を持つ周期媒体内で、これと外れた厚さを有する層では、電磁波の局在が生じる。この現象は、外の二つの周期媒体の反射鏡の中に挟まれているため生じると考えられ、この層を非常に体積の小さい共振器として利用し、レーザー発振を生じうる。すでに、可視光領域では、この現象を使ってトポロジカル・レーザー発振が近年実現されている。本研究はX線がブラッグ反射を起こす周期媒体として結晶を用い、格子間距離の変調が起きている積層欠陥でのブラッグ反射の挙動を理論的に明らかにし、同様のレーザー発振につながる基礎的な成果をもたらした。