| Title: |
Observation of the massive Lee-Fukuyama phason in a charge density wave insulator |
| Authors: |
Kim, Soyeun, Lv, Yinchuan, Sun, Xiao-Qi, Zhao, Chengxi, Bielinski, Nina, Murzabekova, Azel, Qu, Kejian, Duncan, Ryan A., Nguyen, Quynh L. D., Trigo, Mariano, Shoemaker, Daniel P., Bradlyn, Barry, Mahmood, Fahad |
| Publication Year: |
2022 |
| Collection: |
Condensed Matter |
| Subject Terms: |
Condensed Matter - Strongly Correlated Electrons, Condensed Matter - Materials Science |
| More Details: |
The lowest-lying fundamental excitation of an incommensurate charge density wave (CDW) material is widely believed to be a massless phason -- a collective modulation of the phase of the CDW order parameter. However, as first pointed out by Lee and Fukuyama, long-range Coulomb interactions should push the phason energy up to the plasma energy of the CDW condensate, resulting in a massive phason and a fully gapped spectrum. Whether such behavior occurs in a CDW system has been unresolved for more than four decades. Using time-domain THz emission spectroscopy, we investigate this issue in the material (TaSe$_4$)$_2$I, a classical example of a quasi-one-dimensional CDW insulator. Upon transient photoexcitation at low temperatures, we find the material strikingly emits coherent, narrow-band THz radiation. The frequency, polarization and temperature-dependence of the emitted radiation imply the existence of a phason that acquires mass by coupling to long-range Coulomb interaction. Our observations constitute the first direct evidence of the massive "Lee-Fukuyama" phason and highlight the potential applicability of fundamental collective modes of correlated materials as compact and robust sources of THz radiation.
Comment: 6 pages, 4 figures. SI available on request |
| Document Type: |
Working Paper |
| DOI: |
10.1038/s41563-023-01504-5 |
| Access URL: |
http://arxiv.org/abs/2210.14207 |
| Accession Number: |
edsarx.2210.14207 |
| Database: |
arXiv |
