碩博班專題討論(Colloquium)
The Dynamical Charge Response of Plasmons to the Static Charge-Density-Wave Order in CuTe
演講者 : 朱明文博士/ Dr. Ming-Wen Chu - (臺大凝態中心特聘研究員/Center for Condensed Matter Sciences, NTU)
演講地點 :
理學教學新大樓物理系1F 36102教室
演講時間 :
2023 / 05 / 12
14:10
CuTe harbors a quasi-one-dimensional crystal structure, with the onset of charge density wave (CDW) below 335 K [1,2]. This CDW order satisfies all the essential ingredients of the uniaxial lattice modulation, Fermi-surface nesting, and Kohn anomaly in the classical context of the Peierls instability [1].
Conversely, plasmons, being the quanta of dynamical charge oscillations in matters, have been shown to be sensitive to the CDW order by the presence of a negative momentum(q)-dependent dispersion, which reflects the softening of the dynamical response by the CDW [3]. A very recent q-dependent electron-energy loss spectroscopy (q-EELS) study, however, refutes this scenario of the CDW-induced plasmon condensation and points out a rather quadratic q-dispersion in close interaction with the CDW gap [4]. CuTe, with the plasmon excitation at ~2.5 eV [2] and the gap size at the way lower energy scale of ~150 meV [1], stands out as an ideal system for mitigating the direct impact of the single-particle gap excitation on the collective plasmon [4] and could readily unveil the most fundamental aspect on the dynamical charge response in the electronic order of CDWs [2-4]. Using the joint force of q-EELS and atom-resolved EELS (Å-EELS), we have resolved the plasmon dispersions in CuTe as a function of temperatures below 335 K, along with the atomistic insight into the wave modulation in real space. An exotic plasmon-dispersion characteristic in response to the concomitant CDW order-parameter strength was unambiguously observed and will be thoroughly presented in the meeting in light of disentangling the complex physics of the dynamical plasmon response in the presence of the static CDW order.
References
1. Zhang, K. et al. (2018). Evidence for a quasi-one-dimensional charge density wave in CuTe by angle-resolved photoemission spectroscopy. Physical review letters, 121, 206402.
2. Cudazzo, P. & Wirtz, L. (2021). Collective electronic excitations in charge density wave systems: The case of CuTe. Physical review B, 104, 125101.
3. Kogar, A. et al. (2017). Signatures of exciton condensation in a transition metal dichalcogenide. Science, 358, 1314-1317.
4. Lin, Z. et al. (2022). Dramatic plasmon response to the charge-density-wave gap development in 1T-TiSe2. Physical review letters, 129, 187601.
Conversely, plasmons, being the quanta of dynamical charge oscillations in matters, have been shown to be sensitive to the CDW order by the presence of a negative momentum(q)-dependent dispersion, which reflects the softening of the dynamical response by the CDW [3]. A very recent q-dependent electron-energy loss spectroscopy (q-EELS) study, however, refutes this scenario of the CDW-induced plasmon condensation and points out a rather quadratic q-dispersion in close interaction with the CDW gap [4]. CuTe, with the plasmon excitation at ~2.5 eV [2] and the gap size at the way lower energy scale of ~150 meV [1], stands out as an ideal system for mitigating the direct impact of the single-particle gap excitation on the collective plasmon [4] and could readily unveil the most fundamental aspect on the dynamical charge response in the electronic order of CDWs [2-4]. Using the joint force of q-EELS and atom-resolved EELS (Å-EELS), we have resolved the plasmon dispersions in CuTe as a function of temperatures below 335 K, along with the atomistic insight into the wave modulation in real space. An exotic plasmon-dispersion characteristic in response to the concomitant CDW order-parameter strength was unambiguously observed and will be thoroughly presented in the meeting in light of disentangling the complex physics of the dynamical plasmon response in the presence of the static CDW order.
References
1. Zhang, K. et al. (2018). Evidence for a quasi-one-dimensional charge density wave in CuTe by angle-resolved photoemission spectroscopy. Physical review letters, 121, 206402.
2. Cudazzo, P. & Wirtz, L. (2021). Collective electronic excitations in charge density wave systems: The case of CuTe. Physical review B, 104, 125101.
3. Kogar, A. et al. (2017). Signatures of exciton condensation in a transition metal dichalcogenide. Science, 358, 1314-1317.
4. Lin, Z. et al. (2022). Dramatic plasmon response to the charge-density-wave gap development in 1T-TiSe2. Physical review letters, 129, 187601.
