新しい超高速電子顕微鏡技術により、脳のようなコンピューティングに応用可能なプロセスの理解が進む(Novel ultrafast electron microscopy technique advances understanding of processes applicable to brain-like computing)

2024-08-05 アルゴンヌ国立研究所(ANL)

＜関連情報＞

• https://www.anl.gov/article/novel-ultrafast-electron-microscopy-technique-advances-understanding-of-processes-applicable-to
• https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.132.226201

1T-TaS2における電荷密度波の電気的融解におけるナノ秒構造ダイナミクス Nanosecond Structural Dynamics during Electrical Melting of Charge Density Waves in 1⁢T−TaS2

Daniel B. Durham, Thomas E. Gage, Connor P. Horn, Xuedan Ma, Haihua Liu, Ilke Arslan, Supratik Guha, and Charudatta Phatak
Physical Review Letters  Published 28 May 2024
DOI:https://doi.org/10.1103/PhysRevLett.132.226201

Abstract

Electrical control of charge density waves has been of immense interest, as the strong underlying electron-lattice interactions potentially open new, efficient pathways for manipulating their ordering and, consequently, their electronic properties. However, the transition mechanisms are often unclear as electric field, current, carrier injection, heat, and strain can all contribute and play varying roles across length scales and timescales. Here, we provide insight on how electrical stimulation melts the room temperature charge density wave order in 1⁢T−TaS₂ by visualizing the atomic and mesoscopic structural dynamics from quasi-static to nanosecond pulsed melting. Using a newly developed ultrafast electron microscope setup with electrical stimulation, we reveal the order and strain dynamics during voltage pulses as short as 20 ns. The order parameter dynamics across a range of pulse amplitudes and durations support a thermally driven mechanism even for fields as high as 19  kV cm⁻¹. In addition, time-resolved imaging reveals a heterogeneous, mesoscopic strain response across the flake, including MHz-scale acoustic resonances that emerge during sufficiently short pulsed excitation which may modulate the order. These results suggest that metallic charge density wave phases like studied here may be more robust to electronic switching pathways than insulating ones, motivating further investigations at higher fields and currents in this and other related systems.