Nonthermal melting of charge density wave order via nucleation in VTe2

Photoinduced Nonvolatile Displacive Transformation and Optical Switching in MnTe Semiconductors

“…However, as shown in Figure c, the F dependence of T / T 0 in region (i) at different Δ t values resulted in relatively linear decreases without any threshold behaviors, regardless of the probe photon energy (the results monitored under other photon energy are shown in Figure S3 in the Supporting Information). In different cases of PIPTs, the fluence dependence of the change in physical properties, such as reflectivity, and conductivity, exhibits a threshold behavior. ,,,, In this study, we cannot provide any decisive evidence of the reversible transformation between the β- and α-MnTe other than the similarity of the spectral shape in Figure a and the inset in Figure b. The result in Figure a may be simply ascribed to the response of β-MnTe, and it may not be related to a phase transformation.…”

“…In different cases of PIPTs, the fluence dependence of the change in physical properties, such as reflectivity, and conductivity, exhibits a threshold behavior. 12,18,22,23,36 In this study, we cannot provide any decisive evidence of the reversible transformation between the βand α-MnTe other than the similarity of the spectral shape in Figure 3a and the inset in Figure 1b. The result in Figure 3a may be simply ascribed to the response of β-MnTe, and it may not be related to a phase transformation.…”

“…This similarity between the T / T 0 and T α / T β spectra implies partial transient β → α transformation by photoexcitation. Namely, similar to the phase transformation mechanism of other materials, , the small domains (or embryos) of the α phase can be transiently induced in the β-matrix phase. Consequently, the optical properties of the entire sample approach those of the α phase.…”

“…Using an fs-laser, nonthermal photoinduced phase transitions (PIPTs) originating from electron excitations are induced within the picosecond (ps) time region in most cases. , PIPTs proceed as an energy-efficient mechanism that is different from conventional temperature- or pressure-induced phase transition. , For their applications in PCMs, largely different physical properties are required before and after PIPTs. Examples are the ultrafast amorphization of Ge 2 Sb 2 Te 5 (GST), − solid–solid transformation of GeTe, metal–insulator transition of VO 2 , − nonthermal melting of a charge–density–wave order, − and atomic displacement of layered chalcogenide. − However, most of these examples report displacive PIPTs, including the latter three, which has notable volatility; i.e., the photoinduced phase can live only transiently; thus, these cannot be applied for nonvolatile memory. Other works attempted to develop various two-dimensional materials as PCMs using theoretical simulation − while experimental success to demonstrate the photoinduced nonvolatile displacive transformation is surely desired.…”

Unusual photoinduced crystal structure dynamics in TaTe2 with double zigzag chain superstructure

“…For the RT 1 T″-TaTe 2 , we can hypothetically consider the structural change from 1 T″ to 1T-phase, which is realized in the case of VTe 2 . 7,8,18,19,29,34) Nevertheless, we should note that in VTe 2 , much lower fluence of 0.2 mJ cm -2 can induce the structural change as large as >10% in diffraction intensity, whereas A st <2% at 2.4 mJ cm -2 for the present case. We can also consider the possibility of yet unknown hidden states other than 1T-phase.…”