The Experts below are selected from a list of 360 Experts worldwide ranked by ideXlab platform
Yuxia Duan - One of the best experts on this subject based on the ideXlab platform.
-
study of pseudogap and superconducting quasiparticle dynamics in bi2sr2cacu2o8 δ by time resolved Optical Reflectivity
Physica C-superconductivity and Its Applications, 2020Co-Authors: Xiu Zhang, Haiying Song, Xuchen Nie, Yang Wang, Jianqiao Meng, Lin Zhao, Qiang Gao, Xingjiang Zhou, Yuxia DuanAbstract:Abstract The relation between pseudogap (PG) and superconducting (SC) gap, whether PG is a precursor of SC or they coexist or compete, is a long-standing controversy in cuprate high-temperature supercondutors. Here, we report ultrafast time-resolved Optical Reflectivity investigation of the dynamic densities and relaxations of PG and SC quasiparticles (QPs) in the underdoped Bi2Sr2CaCu2O 8 + δ (Tc = 82 K) single crystals. We find evidence of two distinct PG components in the positive Reflectivity changes in the PG state, characterized by relaxation timescales of τfast ≈ 0.2 ps and τslow ≈ 2 ps with abrupt changes in both amplitudes Afast and Aslow at the PG-opening temperature T*. The former presents no obvious change at Tc and coexists with the SC QP. The latter’s amplitude starts decreasing at the SC phase fluctuation Tp and vanishes at Tc followed by a negative amplitude signifying the emergence of the SC QP, therefore suggesting a competition with superconductivity.
-
ultrafast hot carrier dynamics of zrte 5 from time resolved Optical Reflectivity
Physical Review B, 2019Co-Authors: Xiu Zhang, Haiying Song, Xuchen Nie, Shibing Liu, Yang Wang, Congying Jiang, Shizhong Zhao, Genfu Chen, Jianqiao Meng, Yuxia DuanAbstract:${\mathrm{ZrTe}}_{5}$ is a layered pentatelluride with very weak interlayer coupling, high in-plane carrier mobility, and strong electron-electron interaction. We investigate the hot carrier dynamics of ${\mathrm{ZrTe}}_{5}$ by ultrafast time-resolved Optical Reflectivity. Our results reveal a phonon-mediated across-gap recombination and an electron-phonon scattering channel in thermalization, with timescales of few and sub-ps, respectively. In addition we find a fast relaxation right after the initial photoexcitation with a time constant of $\ensuremath{\sim}250$ fs, possibly arising from an electron-electron scattering channel. Our findings indicate that correlated many-body effects play an important role for the transient dynamics of ${\mathrm{ZrTe}}_{5}$.
-
photoinduced two step insulator metal transition in ti4o7 via ultrafast time resolved Optical Reflectivity
Applied Physics Express, 2018Co-Authors: Xuchen Nie, Xiu Zhang, Haiying Song, Shibing Liu, Jianqiao Meng, Yuxia Duan, Lili Yue, Lin Zhao, Haiyun LiuAbstract:We report on the systematic investigation of hot carrier dynamics in Ti4O7 by ultrafast time-resolved Optical Reflectivity. We find the transient indication for its two-step insulator–metal (I–M) transition, i.e., from the long-range ordered bipolaron low-temperature insulating phase to the disordered bipolaron high-temperature insulating phase at T c1 and to the free-carrier metallic phase at T c2. Our results reveal that photoexcitation can effectively reduce both T c1 and T c2 by increasing the pump fluence, allowing the light-control of the I–M transition. We address a phase diagram that provides a framework for the photoinduced I–M transition and helps the potential use of Ti4O7 for photoelectric and thermoelectric devices.
Xuchen Nie - One of the best experts on this subject based on the ideXlab platform.
-
study of pseudogap and superconducting quasiparticle dynamics in bi2sr2cacu2o8 δ by time resolved Optical Reflectivity
Physica C-superconductivity and Its Applications, 2020Co-Authors: Xiu Zhang, Haiying Song, Xuchen Nie, Yang Wang, Jianqiao Meng, Lin Zhao, Qiang Gao, Xingjiang Zhou, Yuxia DuanAbstract:Abstract The relation between pseudogap (PG) and superconducting (SC) gap, whether PG is a precursor of SC or they coexist or compete, is a long-standing controversy in cuprate high-temperature supercondutors. Here, we report ultrafast time-resolved Optical Reflectivity investigation of the dynamic densities and relaxations of PG and SC quasiparticles (QPs) in the underdoped Bi2Sr2CaCu2O 8 + δ (Tc = 82 K) single crystals. We find evidence of two distinct PG components in the positive Reflectivity changes in the PG state, characterized by relaxation timescales of τfast ≈ 0.2 ps and τslow ≈ 2 ps with abrupt changes in both amplitudes Afast and Aslow at the PG-opening temperature T*. The former presents no obvious change at Tc and coexists with the SC QP. The latter’s amplitude starts decreasing at the SC phase fluctuation Tp and vanishes at Tc followed by a negative amplitude signifying the emergence of the SC QP, therefore suggesting a competition with superconductivity.
-
ultrafast hot carrier dynamics of zrte 5 from time resolved Optical Reflectivity
Physical Review B, 2019Co-Authors: Xiu Zhang, Haiying Song, Xuchen Nie, Shibing Liu, Yang Wang, Congying Jiang, Shizhong Zhao, Genfu Chen, Jianqiao Meng, Yuxia DuanAbstract:${\mathrm{ZrTe}}_{5}$ is a layered pentatelluride with very weak interlayer coupling, high in-plane carrier mobility, and strong electron-electron interaction. We investigate the hot carrier dynamics of ${\mathrm{ZrTe}}_{5}$ by ultrafast time-resolved Optical Reflectivity. Our results reveal a phonon-mediated across-gap recombination and an electron-phonon scattering channel in thermalization, with timescales of few and sub-ps, respectively. In addition we find a fast relaxation right after the initial photoexcitation with a time constant of $\ensuremath{\sim}250$ fs, possibly arising from an electron-electron scattering channel. Our findings indicate that correlated many-body effects play an important role for the transient dynamics of ${\mathrm{ZrTe}}_{5}$.
-
photoinduced two step insulator metal transition in ti4o7 via ultrafast time resolved Optical Reflectivity
Applied Physics Express, 2018Co-Authors: Xuchen Nie, Xiu Zhang, Haiying Song, Shibing Liu, Jianqiao Meng, Yuxia Duan, Lili Yue, Lin Zhao, Haiyun LiuAbstract:We report on the systematic investigation of hot carrier dynamics in Ti4O7 by ultrafast time-resolved Optical Reflectivity. We find the transient indication for its two-step insulator–metal (I–M) transition, i.e., from the long-range ordered bipolaron low-temperature insulating phase to the disordered bipolaron high-temperature insulating phase at T c1 and to the free-carrier metallic phase at T c2. Our results reveal that photoexcitation can effectively reduce both T c1 and T c2 by increasing the pump fluence, allowing the light-control of the I–M transition. We address a phase diagram that provides a framework for the photoinduced I–M transition and helps the potential use of Ti4O7 for photoelectric and thermoelectric devices.
Mercouri G Kanatzidis - One of the best experts on this subject based on the ideXlab platform.
-
high temperature charge and thermal transport properties of the n type thermoelectric material pbse
Physical Review B, 2011Co-Authors: John Androulakis, Duck Young Chung, Li Zhang, Ctirad Uher, Thomas C Hasapis, E Hatzikraniotis, K M Paraskevopoulos, Mercouri G KanatzidisAbstract:We present a detailed study of the charge transport, infrared Optical Reflectivity, and thermal transport properties of n-type PbSe crystals. A strong scattering, mobility-limiting mechanism was revealed to be at play at temperatures above 500 K. The mechanism is indicative of complex electron-phonon interactions that cannot be explained by conventional acoustic phonon scattering alone. We applied the first-order nonparabolicity approximation to extract the density-of-states effective mass as a function of doping both at room temperature and at 700 K. The results are compared to those of a parabolic band model and in light of doping-dependent studies of the infrared Optical Reflectivity. The thermal conductivity behavior as a function of temperature shows a strong deviation from the expected Debye-Peierls high-temperature behavior (umklapp dominated) indicating an additional heat-carrying channel, which we associate with Optical phonon excitations. The correlation of the thermal conductivity observations to the high-temperature carrier mobility behavior is discussed. The thermoelectric figure of merit exhibits a promising value of {approx} 0.8 at 700 K at {approx} 1.5 x 10{sup 19} cm{sup -3}.
Delphine Débarre - One of the best experts on this subject based on the ideXlab platform.
-
the conformation of thermoresponsive polymer brushes probed by Optical Reflectivity
Langmuir, 2016Co-Authors: Siddhartha Varma, Lionel Bureau, Delphine DébarreAbstract:We describe a microscope-based Optical setup that allows us to perform space- and time-resolved measurements of the spectral reflectance of transparent substrates coated with ultrathin films. This technique is applied to investigate the behavior in water of thermosensitive polymer brushes made of poly(N-isopropylacrylamide) grafted on glass. We show that spectral reflectance measurements yield quantitative information about the conformation and axial structure of the brushes as a function of temperature. We study how parameters such as grafting density and chain length affect the hydration state of a brush, and provide one of the few experimental evidences for the occurrence of vertical phase separation in the vicinity of the lower critical solution temperature of the polymer. The origin of the hysteretic behavior of poly(N-isopropylacrylamide) brushes upon cycling the temperature is also clarified. We thus demonstrate that our Optical technique allows for in-depth characterization of stimuli-responsive p...
-
The conformation of thermoresponsive polymer brushes probed by Optical Reflectivity
2016Co-Authors: Siddhartha Varma, Lionel Bureau, Delphine DébarreAbstract:We describe a microscope-based Optical setup that allows us to perform space-and time-resolved measurements of the spectral reflectance of transparent substrates coated with ultrathin films. This technique is applied to investigate the behavior in water of thermosensitive polymer brushes made of poly(N-isopropylacrylamide) grafted on glass. We show that spectral reflectance measurements yield quantitative information about the conformation and axial structure of the brushes as a function of temperature. We study how molecular parameters (grafting density, chain length) affect the hydra-tion state of a brush, and provide one of the few experimental evidence for the occurrence of vertical phase separation in the vicinity of the lower critical solution temperature of the polymer. The origin of the hysteretic behavior of poly(N-isopropylacrylamide) brushes upon cycling the temperature is also clarified. We thus demonstrate that our Optical technique allows for in-depth characterization of stimuli-responsive polymer layers, which is crucial for the rational design of smart polymer coatings in actuation, gating or sensing applications.
Xiu Zhang - One of the best experts on this subject based on the ideXlab platform.
-
study of pseudogap and superconducting quasiparticle dynamics in bi2sr2cacu2o8 δ by time resolved Optical Reflectivity
Physica C-superconductivity and Its Applications, 2020Co-Authors: Xiu Zhang, Haiying Song, Xuchen Nie, Yang Wang, Jianqiao Meng, Lin Zhao, Qiang Gao, Xingjiang Zhou, Yuxia DuanAbstract:Abstract The relation between pseudogap (PG) and superconducting (SC) gap, whether PG is a precursor of SC or they coexist or compete, is a long-standing controversy in cuprate high-temperature supercondutors. Here, we report ultrafast time-resolved Optical Reflectivity investigation of the dynamic densities and relaxations of PG and SC quasiparticles (QPs) in the underdoped Bi2Sr2CaCu2O 8 + δ (Tc = 82 K) single crystals. We find evidence of two distinct PG components in the positive Reflectivity changes in the PG state, characterized by relaxation timescales of τfast ≈ 0.2 ps and τslow ≈ 2 ps with abrupt changes in both amplitudes Afast and Aslow at the PG-opening temperature T*. The former presents no obvious change at Tc and coexists with the SC QP. The latter’s amplitude starts decreasing at the SC phase fluctuation Tp and vanishes at Tc followed by a negative amplitude signifying the emergence of the SC QP, therefore suggesting a competition with superconductivity.
-
ultrafast hot carrier dynamics of zrte 5 from time resolved Optical Reflectivity
Physical Review B, 2019Co-Authors: Xiu Zhang, Haiying Song, Xuchen Nie, Shibing Liu, Yang Wang, Congying Jiang, Shizhong Zhao, Genfu Chen, Jianqiao Meng, Yuxia DuanAbstract:${\mathrm{ZrTe}}_{5}$ is a layered pentatelluride with very weak interlayer coupling, high in-plane carrier mobility, and strong electron-electron interaction. We investigate the hot carrier dynamics of ${\mathrm{ZrTe}}_{5}$ by ultrafast time-resolved Optical Reflectivity. Our results reveal a phonon-mediated across-gap recombination and an electron-phonon scattering channel in thermalization, with timescales of few and sub-ps, respectively. In addition we find a fast relaxation right after the initial photoexcitation with a time constant of $\ensuremath{\sim}250$ fs, possibly arising from an electron-electron scattering channel. Our findings indicate that correlated many-body effects play an important role for the transient dynamics of ${\mathrm{ZrTe}}_{5}$.
-
photoinduced two step insulator metal transition in ti4o7 via ultrafast time resolved Optical Reflectivity
Applied Physics Express, 2018Co-Authors: Xuchen Nie, Xiu Zhang, Haiying Song, Shibing Liu, Jianqiao Meng, Yuxia Duan, Lili Yue, Lin Zhao, Haiyun LiuAbstract:We report on the systematic investigation of hot carrier dynamics in Ti4O7 by ultrafast time-resolved Optical Reflectivity. We find the transient indication for its two-step insulator–metal (I–M) transition, i.e., from the long-range ordered bipolaron low-temperature insulating phase to the disordered bipolaron high-temperature insulating phase at T c1 and to the free-carrier metallic phase at T c2. Our results reveal that photoexcitation can effectively reduce both T c1 and T c2 by increasing the pump fluence, allowing the light-control of the I–M transition. We address a phase diagram that provides a framework for the photoinduced I–M transition and helps the potential use of Ti4O7 for photoelectric and thermoelectric devices.