Chalcogenide superlattices Sb_(2)Te_(3)-GeTe is a candidate for interfacial phase-change memory(iPCM) data storage devices.By employing terahertz emission spectroscopy and the transient reflectance spectroscopy togeth...Chalcogenide superlattices Sb_(2)Te_(3)-GeTe is a candidate for interfacial phase-change memory(iPCM) data storage devices.By employing terahertz emission spectroscopy and the transient reflectance spectroscopy together,we investigate the ultrafast photoexcited carrier dynamics and current transients in Sb_(2)Te_(3)-GeTe superlattices.Sample orientation and excitation polarization dependences of the THz emission confirm that ultrafast thermo-electric,shift and injection currents contribute to the THz generation in Sb_(2)Te_(3)-GeTe superlattices.By decreasing the thickness and increasing the number of GeTe and Sb_(2)Te_(3) layer,the interlayer coupling can be enhanced,which significantly reduces the contribution from circular photo-galvanic effect(CPGE).A photo-induced bleaching in the transient reflectance spectroscopy probed in the range of~1100 nm to~1400 nm further demonstrates a gapped state resulting from the interlayer coupling.These demonstrates play an important role in the development of iPCM-based high-speed optoelectronic devices.展开更多
We investigate the nonlocal optical conductivity of Fermi surface nesting materials that support charge density waves(CDWs)or spin density waves(SDWs).The nonlocal optical conductivity contains information on correlat...We investigate the nonlocal optical conductivity of Fermi surface nesting materials that support charge density waves(CDWs)or spin density waves(SDWs).The nonlocal optical conductivity contains information on correlations in electron fluids,which could not be accessed by standard optical probes.A half-metal emerges from doping a CDW,and similarly,a spin-valley halfmetal emerges from doping an SDW.Based on the parabolic band approximation,we find that the Drude peak is shifted to a higher frequency and splits into two peaks in the nonlocal optical conductivity.We attribute this to the two Fermi velocities in the half-metal or spin-valley half-metal states.展开更多
基金Project supported by the National Key Research and Development Program of China(Grant Nos.2023YFF0719200 and 2022YFA1404004)the National Natural Science Foundation of China(Grant Nos.62322115,61988102,61975110,62335012,and 12074248)+3 种基金111 Project(Grant No.D18014)the Key Project supported by Science and Technology Commission Shanghai Municipality(Grant No.YDZX20193100004960)Science and Technology Commission of Shanghai Municipality(Grant Nos.22JC1400200 and 21S31907400)General Administration of Customs People’s Republic of China(Grant No.2019HK006)。
文摘Chalcogenide superlattices Sb_(2)Te_(3)-GeTe is a candidate for interfacial phase-change memory(iPCM) data storage devices.By employing terahertz emission spectroscopy and the transient reflectance spectroscopy together,we investigate the ultrafast photoexcited carrier dynamics and current transients in Sb_(2)Te_(3)-GeTe superlattices.Sample orientation and excitation polarization dependences of the THz emission confirm that ultrafast thermo-electric,shift and injection currents contribute to the THz generation in Sb_(2)Te_(3)-GeTe superlattices.By decreasing the thickness and increasing the number of GeTe and Sb_(2)Te_(3) layer,the interlayer coupling can be enhanced,which significantly reduces the contribution from circular photo-galvanic effect(CPGE).A photo-induced bleaching in the transient reflectance spectroscopy probed in the range of~1100 nm to~1400 nm further demonstrates a gapped state resulting from the interlayer coupling.These demonstrates play an important role in the development of iPCM-based high-speed optoelectronic devices.
基金supported by the ISSP International Collaboration Program of the University of Tokyothe support of a JSPS Foreign Postdoctoral Fellowship(Grant Nos.PE14052,P16027)+4 种基金the Chinese Academy of Sciences funding(Grant Nos.E1Z1D10200,and E2Z2D10200)supported by the National Natural Science Foundation of China(Grant No.61988102)the Key Research and Development Program of Guangdong Province(Grant No.2019B090917007)the Science and Technology Planning Project of Guangdong Province(Grant No.2019B090909011)the ZJ project(Grant No.2021QN02X159)。
文摘We investigate the nonlocal optical conductivity of Fermi surface nesting materials that support charge density waves(CDWs)or spin density waves(SDWs).The nonlocal optical conductivity contains information on correlations in electron fluids,which could not be accessed by standard optical probes.A half-metal emerges from doping a CDW,and similarly,a spin-valley halfmetal emerges from doping an SDW.Based on the parabolic band approximation,we find that the Drude peak is shifted to a higher frequency and splits into two peaks in the nonlocal optical conductivity.We attribute this to the two Fermi velocities in the half-metal or spin-valley half-metal states.
