Angle-resolved photoemission spectroscopy(ARPES)and torque magnetometry(TM)measurements have been carried out to study the electronic structures of a correlated topological insulator(TI)candidate Yb B6.We observed cle...Angle-resolved photoemission spectroscopy(ARPES)and torque magnetometry(TM)measurements have been carried out to study the electronic structures of a correlated topological insulator(TI)candidate Yb B6.We observed clear surface states on the[001]surface centered at theГ^- and М^- points of the surface Brillouin zone.Interestingly,the fermiology revealed by the quantum oscillation of TM measurements agrees excellently with ARPES measurements.Moreover,the band structures we observed suggest that the band inversion in Yb B6 happens between the Yb5 dand B2bands,instead of the Yb5dand Yb4fbands as suggested by previous theoretical investigation,which will help settle the heavy debate regarding the topological nature of samarium/ytterbium hexaborides.展开更多
Thermoelectric materials(TMs)can uniquely convert waste heat into electricity,which provides a potential solution for the global energy crisis that is increasingly severe.Bulk Cu2Se,with ionic conductivity of Cu ions,...Thermoelectric materials(TMs)can uniquely convert waste heat into electricity,which provides a potential solution for the global energy crisis that is increasingly severe.Bulk Cu2Se,with ionic conductivity of Cu ions,exhibits a significant enhancement of its thermoelectric figure of merit z T by a factor of^3 near its structural transition around 400 K.Here,we show a systematic study of the electronic structure of Cu2Se and its temperature evolution using high-resolution angle-resolved photoemission spectroscopy.Upon heating across the structural transition,the electronic states near the corner of the Brillouin zone gradually disappear,while the bands near the centre of Brillouin zone shift abruptly towards high binding energies and develop an energy gap.Interestingly,the observed band reconstruction well reproduces the temperature evolution of the Seebeck coefficient of Cu2 Se,providing an electronic origin for the drastic enhancement of the thermoelectric performance near 400 K.The current results not only bridge among structural phase transition,electronic structures and thermoelectric properties in a condensed matter system,but also provide valuable insights into the search and design of new generation of thermoelectric materials.展开更多
基金supported by the National Natural Science Foundation of China (Grant Nos. 11774190, 11674229, 11634009, and 11774427)the National Key R&D Program of China (Grant Nos. 2017YFA0304600 and 2017YFA0305400)+5 种基金support from the EPSRC (UK) grant EP/K04074X/1 and a DARPA (US) MESO project (No. N66001-11-1-4105)supported by the Office of Naval Research through the National Science Foundation under Award No. DMR-1707620 (magnetization measurement)supported by the Office of Basic Energy Sciences of the U.S. Department of Energy (DE-AC0205CH11231)SIMES and SLAC National Accelerator Laboratory is supported by the Office of Basic Energy Sciences of the U.S. Department of Energy (DE-AC0276SF00515)Nanjing University is supported by the National Basic Research Program of China (Grant No. 51002074)the National Basic Research of China (Grant Nos. 2012CB921503 and 2012CB632702)
文摘Angle-resolved photoemission spectroscopy(ARPES)and torque magnetometry(TM)measurements have been carried out to study the electronic structures of a correlated topological insulator(TI)candidate Yb B6.We observed clear surface states on the[001]surface centered at theГ^- and М^- points of the surface Brillouin zone.Interestingly,the fermiology revealed by the quantum oscillation of TM measurements agrees excellently with ARPES measurements.Moreover,the band structures we observed suggest that the band inversion in Yb B6 happens between the Yb5 dand B2bands,instead of the Yb5dand Yb4fbands as suggested by previous theoretical investigation,which will help settle the heavy debate regarding the topological nature of samarium/ytterbium hexaborides.
基金the National Natural Science Foundation of China(11774190,11674229,11634009 and 11874264)the National Key R&D Program of China(2017YFA0304600,2017YFA0305400 and 2017YFA0402900)+2 种基金EPSRC Platform Grant(EP/M020517/1)the support from the Natural Science Foundation of Shanghai(17ZR1443300)the support from Tsinghua University Initiative Scientific Research Program。
文摘Thermoelectric materials(TMs)can uniquely convert waste heat into electricity,which provides a potential solution for the global energy crisis that is increasingly severe.Bulk Cu2Se,with ionic conductivity of Cu ions,exhibits a significant enhancement of its thermoelectric figure of merit z T by a factor of^3 near its structural transition around 400 K.Here,we show a systematic study of the electronic structure of Cu2Se and its temperature evolution using high-resolution angle-resolved photoemission spectroscopy.Upon heating across the structural transition,the electronic states near the corner of the Brillouin zone gradually disappear,while the bands near the centre of Brillouin zone shift abruptly towards high binding energies and develop an energy gap.Interestingly,the observed band reconstruction well reproduces the temperature evolution of the Seebeck coefficient of Cu2 Se,providing an electronic origin for the drastic enhancement of the thermoelectric performance near 400 K.The current results not only bridge among structural phase transition,electronic structures and thermoelectric properties in a condensed matter system,but also provide valuable insights into the search and design of new generation of thermoelectric materials.
