Doping-controlled transition from excitonic insulator to semimetal in Ta$_2$NiSe$_5$
| Autor: | Z. M. Xin, Y. Zhang, Y. D. Wang, Zhengguo Wang, C. Cai, Tingting Han, Li Chen |
|---|---|
| Jazyk: | angličtina |
| Rok vydání: | 2020 |
| Předmět: |
Physics
Condensed Matter::Quantum Gases Condensed Matter - Materials Science Strongly Correlated Electrons (cond-mat.str-el) Condensed matter physics Photoemission spectroscopy Condensed Matter::Other Exciton Condensed Matter - Superconductivity Doping Binding energy Materials Science (cond-mat.mtrl-sci) FOS: Physical sciences Angle-resolved photoemission spectroscopy 02 engineering and technology Electronic structure 021001 nanoscience & nanotechnology 01 natural sciences Semimetal Superconductivity (cond-mat.supr-con) Condensed Matter - Strongly Correlated Electrons 0103 physical sciences 010306 general physics 0210 nano-technology Electronic band structure |
| Popis: | Excitonic insulator (EI) is an intriguing insulating phase of matter, where electrons and holes are bonded into pairs, so called excitons, and form a phase-coherent state via Bose-Einstein Condensation (BEC). Its theoretical concept has been proposed several decades ago, but the followed research is very limited, due to the rare occurrence of EI in natural materials and the lack of manipulating method of excitonic condensation. In this paper, we report the realization of a doping-controlled EI-to-semi-metal transition in Ta$_2$NiSe$_5$ using $in$-$situ$ potassium deposition. Combining with angle-resolved photoemission spectroscopy (ARPES), we delineate the evolution of electronic structure through the EI transition with unprecedented precision. The results not only show that Ta$ _2 $NiSe$ _5 $ (TNS) is an EI originated from a semi-metal non-interacting band structure, but also resolve two sequential transitions, which could be attributed to the phase-decoherence and pair-breaking respectively. Our results unveil the Bardeen-Cooper-Schrieffer (BCS)-BEC crossover behavior of TNS and demonstrate that its band structure and excitonic binding energy can be tuned precisely via alkali-metal deposition. This paves a way for investigations of BCS-BEC crossover phenomena, which could provide insights into the many-body physics in condensed matters and other many-body systems. 5 pages, 4 figures, See Supplemental Material at http://link.aps.org/supplemental/ 10.1103/PhysRevB.102.161116 |
| Databáze: | OpenAIRE |
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