As a special order of electronic correlation induced by spatial modulation, the charge density wave(CDW) phenomena in condensed matters attract enormous research interests. Here, using scanning-tunneling microscopy in...As a special order of electronic correlation induced by spatial modulation, the charge density wave(CDW) phenomena in condensed matters attract enormous research interests. Here, using scanning-tunneling microscopy in various temperatures, we discover a hidden incommensurate stripe-like CDW order besides the(■) CDW phase at low-temperature of 4 K in the epitaxial monolayer 1T-VSe_(2) film. Combining the variable-temperature angle-resolved photoemission spectroscopic(ARPES) measurements, we discover a two-step transition of an anisotropic CDW gap structure that consists of two parts △_(1) and△_(2). The gap part ?1 that closes around ~ 150 K is accompanied with the vanish of the(√7×√3) CDW phase. While another momentum-dependent gap part △_(2) can survive up to ~ 340 K, and is suggested to the result of the incommensurate CDW phase. This two-step transition with anisotropic gap opening and the resulted evolution in ARPES spectra are corroborated by our theoretical calculation based on a phenomenological form for the self-energy containing a two-gap structure △_(1) +△_(2), which suggests different forming mechanisms between the(√7×√3) and the incommensurate CDW phases. Our findings provide significant information and deep understandings on the CDW phases in monolayer 1T-VSe_(2) film as a two-dimensional(2D) material.展开更多
Understanding the interplay between superconductivity and charge-density wave(CDW)in NbSe_(2) is vital for both fundamental physics and future device applications.Here,combining scanning tunneling microscopy,anglereso...Understanding the interplay between superconductivity and charge-density wave(CDW)in NbSe_(2) is vital for both fundamental physics and future device applications.Here,combining scanning tunneling microscopy,angleresolved photoemission spectroscopy and Raman spectroscopy,we study the CDW phase in the monolayer NbSe_(2) films grown on various substrates of bilayer graphene(BLG),SrTiO_(3)(111),and Al_(2)O_(3)(0001).It is found that the two stable CDW states of monolayer NbSe_(2) can coexist on NbSe2/BLG surface at liquid-nitrogen temperature.For the NbSe_(2)/SrTiO_(3)(111)sample,the unidirectional CDW regions own the kinks at±41 meV and a wider gap at 4.2 K.It is revealed that the charge transfer from the substrates to the grown films will influence the configurations of the Fermi surface,and induce a 130 meV lift-up of the Fermi level with a shrink of the Fermi pockets in NbSe_(2)/SrTiO_(3)(111)compared with the NbSe2/BLG.Combining the temperature-dependent Raman experiments,we suggest that the electron-phonon coupling in monolayer NbSe2 dominates its CDW phase transition.展开更多
基金Project supported by the National Natural Science Foundation of China (Grant Nos. 92165205, 11790311, 12004172, 11774152, 11604366, and 11634007)the National Key Research and Development Program of China (Grant Nos. 2018YFA0306800 and 2016YFA0300401)+1 种基金the Program of High-Level Entrepreneurial and Innovative Talents Introduction of Jiangsu Province, the Jiangsu Planned Projects for Postdoctoral Research Funds (Grant No. 2020Z172)the Natural Science Foundation of Jiangsu Province, China (Grant No. BK 20160397)。
文摘As a special order of electronic correlation induced by spatial modulation, the charge density wave(CDW) phenomena in condensed matters attract enormous research interests. Here, using scanning-tunneling microscopy in various temperatures, we discover a hidden incommensurate stripe-like CDW order besides the(■) CDW phase at low-temperature of 4 K in the epitaxial monolayer 1T-VSe_(2) film. Combining the variable-temperature angle-resolved photoemission spectroscopic(ARPES) measurements, we discover a two-step transition of an anisotropic CDW gap structure that consists of two parts △_(1) and△_(2). The gap part ?1 that closes around ~ 150 K is accompanied with the vanish of the(√7×√3) CDW phase. While another momentum-dependent gap part △_(2) can survive up to ~ 340 K, and is suggested to the result of the incommensurate CDW phase. This two-step transition with anisotropic gap opening and the resulted evolution in ARPES spectra are corroborated by our theoretical calculation based on a phenomenological form for the self-energy containing a two-gap structure △_(1) +△_(2), which suggests different forming mechanisms between the(√7×√3) and the incommensurate CDW phases. Our findings provide significant information and deep understandings on the CDW phases in monolayer 1T-VSe_(2) film as a two-dimensional(2D) material.
基金Supported by the National Natural Science Foundation of China (Grant Nos. 11774154, 11790311, and 12004172)the National Key Research and Development Program of China (Grant No. 2018YFA0306800)+3 种基金the Fundamental Research Funds for the Central Universities (Grant No. 0204-14380186)the Jiangsu Planned Projects for Postdoctoral Research Funds (Grant No. 2020Z172)the Program for High-Level Entrepreneurial and Innovative Talents Introduction of Jiangsu Provincethe Program B for Outstanding Ph.D. Candidates of Nanjing University
文摘Understanding the interplay between superconductivity and charge-density wave(CDW)in NbSe_(2) is vital for both fundamental physics and future device applications.Here,combining scanning tunneling microscopy,angleresolved photoemission spectroscopy and Raman spectroscopy,we study the CDW phase in the monolayer NbSe_(2) films grown on various substrates of bilayer graphene(BLG),SrTiO_(3)(111),and Al_(2)O_(3)(0001).It is found that the two stable CDW states of monolayer NbSe_(2) can coexist on NbSe2/BLG surface at liquid-nitrogen temperature.For the NbSe_(2)/SrTiO_(3)(111)sample,the unidirectional CDW regions own the kinks at±41 meV and a wider gap at 4.2 K.It is revealed that the charge transfer from the substrates to the grown films will influence the configurations of the Fermi surface,and induce a 130 meV lift-up of the Fermi level with a shrink of the Fermi pockets in NbSe_(2)/SrTiO_(3)(111)compared with the NbSe2/BLG.Combining the temperature-dependent Raman experiments,we suggest that the electron-phonon coupling in monolayer NbSe2 dominates its CDW phase transition.
基金supported by the National Key Research and Development Program of China(2018YFA0306800,2021YFA1400400,2018YFA0306200,and 2021YFA1202901)the National Natural Science Foundation of China(92165205,11790311,12004172,51861145201,52072168,21733001,and 91750101)+2 种基金the Innovation Program for Quantum Science and Technology for China(2021ZD0302803)the Jiangsu Planned Projects for Postdoctoral Research Funds(2020Z172)the Program of High-Level Entrepreneurial and Innovative Talents Introduction of Jiangsu Province,China。
