The structural features and three-dimensional nature of the charge density wave(CDW) state of the layered chalcogenide 1 T-TaSe_(2-x)Te_x(0≤x≤2.0) are characterized by Cs-corrected transmission electron microscopy m...The structural features and three-dimensional nature of the charge density wave(CDW) state of the layered chalcogenide 1 T-TaSe_(2-x)Te_x(0≤x≤2.0) are characterized by Cs-corrected transmission electron microscopy measurements. Notable changes of both average structure and the CDW state arising from Te substitution for Se are clearly demonstrated in samples with x > 0.3. The commensurate CDW state characterized by the known star-of-David clustering in the 1 T-TaSe_2 crystal becomes visibly unstable with Te substitution and vanishes when x=0.3. The 1 T-TaSe_(2-x)Te_x(0.3≤x≤1.3) samples generalily adopt a remarkable incommensurate CDW state with monoclinic distortion, which could be fundamentally in correlation with the strong q-dependent electronphonon coupling-induced period-lattice-distortion as identified in TaTe2. Systematic analysis demonstrates that the occurrence of superconductivity is related to the suppression of the commensurate CDW phase and the presence of discommensuration is an evident structural feature observed in the superconducting samples.展开更多
A theoretical study on the structural dynamics of the temporal behavior of Bragg diffraction is presented and compared with experimental results obtained via ultrafast electron crystallography.In order to describe the...A theoretical study on the structural dynamics of the temporal behavior of Bragg diffraction is presented and compared with experimental results obtained via ultrafast electron crystallography.In order to describe the time-dependent lattices and calculate the Bragg diffraction intensity,we introduce the basic vector offset matrix,which can be used to quantify the shortening,lengthening and rotation of the three lattice vectors(i.e.,lattice deformation).Extensive simulations are performed to evaluate the four-dimensional electron crystallography model.The results elucidate the connection between structural deformations and changes in diffraction peaks,and sheds light on the quantitative analysis and comprehensive understanding of the structural dynamics.展开更多
基金Supported by the National Basic Research Program of China under Grant Nos 2015CB921300 and 2012CB821404the National Key Research and Development Program of China under Grant Nos 2016YFA0300300 and 2016YFA0300404+1 种基金the National Natural Science Foundation of China under Grant Nos 11474323,11604372,11274368,91221102,11190022,11674326 and 91422303the Strategic Priority Research Program(B)of the Chinese Academy of Sciences under Grant No XDB07020000
文摘The structural features and three-dimensional nature of the charge density wave(CDW) state of the layered chalcogenide 1 T-TaSe_(2-x)Te_x(0≤x≤2.0) are characterized by Cs-corrected transmission electron microscopy measurements. Notable changes of both average structure and the CDW state arising from Te substitution for Se are clearly demonstrated in samples with x > 0.3. The commensurate CDW state characterized by the known star-of-David clustering in the 1 T-TaSe_2 crystal becomes visibly unstable with Te substitution and vanishes when x=0.3. The 1 T-TaSe_(2-x)Te_x(0.3≤x≤1.3) samples generalily adopt a remarkable incommensurate CDW state with monoclinic distortion, which could be fundamentally in correlation with the strong q-dependent electronphonon coupling-induced period-lattice-distortion as identified in TaTe2. Systematic analysis demonstrates that the occurrence of superconductivity is related to the suppression of the commensurate CDW phase and the presence of discommensuration is an evident structural feature observed in the superconducting samples.
基金Supported by the Strategic Priority Research Program of the Chinese Academy of Sciences under Grant No XDB07020200the National Basic Research Program of China under Grant Nos 2012CB821402,2011CBA00109 and 2011CBA00101the National Natural Science Foundation of China under Grant No 11204362
基金Supported by the National Key Research and Development Program of China under Grant Nos.2016YFA0300303,2017YFA0504703,and 2017YFA0302904the National Basic Research Program of China under Grant No.2015CB921304+2 种基金the National Natural Science Foundation of China under Grant Nos.11604372,11474323,11774391,11774403,and 61575085the Strategic Priority Research Program(B)of the Chinese Academy of Sciences under Grant No.XDB25000000the Scientific Instrument Developing Project of the Chinese Academy of Sciences under Grant No.ZDKYYQ20170002。
文摘A theoretical study on the structural dynamics of the temporal behavior of Bragg diffraction is presented and compared with experimental results obtained via ultrafast electron crystallography.In order to describe the time-dependent lattices and calculate the Bragg diffraction intensity,we introduce the basic vector offset matrix,which can be used to quantify the shortening,lengthening and rotation of the three lattice vectors(i.e.,lattice deformation).Extensive simulations are performed to evaluate the four-dimensional electron crystallography model.The results elucidate the connection between structural deformations and changes in diffraction peaks,and sheds light on the quantitative analysis and comprehensive understanding of the structural dynamics.
