Two-dimensional honeycomb crystals have inspired intense research interest for their novel properties and great potential in electronics and optoelectronics. Here, through molecular beam epitaxy on SrTiO_3(001), we re...Two-dimensional honeycomb crystals have inspired intense research interest for their novel properties and great potential in electronics and optoelectronics. Here, through molecular beam epitaxy on SrTiO_3(001), we report successful epitaxial growth of metal-rich chalcogenide Fe_(2)Te, a honeycomb-structured film that has no direct bulk analogue, under Te-limited growth conditions. The structural morphology and electronic properties of Fe_(2)Te are explored with scanning tunneling microscopy and angle resolved photoemission spectroscopy, which reveal electronic bands cross the Fermi level and nearly flat bands. Moreover, we find a weak interfacial interaction between Fe_(2)Te and the underlying substrates, paving a newly developed alternative avenue for honeycomb-based electronic devices.展开更多
Unusual quantum phenomena usually emerge upon doping Mott insulators.Using a molecular beam epitaxy system integrated with cryogenic sc√annin√g tunneling microscope,we investigate the electronic structure of a modul...Unusual quantum phenomena usually emerge upon doping Mott insulators.Using a molecular beam epitaxy system integrated with cryogenic sc√annin√g tunneling microscope,we investigate the electronic structure of a modulation-doped Mott insulator Sn/Si(111)-(√3×√3)R30°.In underdoped regions,we observe a universal pseudogap opening around the Fermi level,which changes little with the applied magnetic field and the occurrence of Sn vacancies.The pseudogap gets smeared out at elevated temperatures and alters in size with the spatial confinement of the Mott insulating phase.Our findings,along with the previously observed superconductivity at a higher doping level,are highly reminiscent of the electronic phase diagram in the doped copper oxide compounds.展开更多
In paired Fermi systems,strong many-body effects exhibit in the crossover regime between the Bardeen–Cooper–Schrieffer(BCS)and the Bose–Einstein condensation(BEC)limits.The concept of the BCS–BEC crossover,which i...In paired Fermi systems,strong many-body effects exhibit in the crossover regime between the Bardeen–Cooper–Schrieffer(BCS)and the Bose–Einstein condensation(BEC)limits.The concept of the BCS–BEC crossover,which is studied intensively in the research field of cold atoms,has been extended to condensed matters.Here by analyzing the typical superconductors within the BCS–BEC phase diagram,we find that FeSe-based superconductors are prone to shift their positions in the BCS–BEC crossover regime by charge doping or substrate substitution,since their Fermi energies and the superconducting gap sizes are comparable.Especially at the interface of single-layer FeSe on SrTiO3 substrate,the superconductivity is relocated closer to the crossover unitary than other doped FeSe-based materials,indicating that the pairing interaction is effectively modulated.We further show that hole-doping can drive the interfacial system into the phase with possible pre-paired electrons,demonstrating its flexible tunability within the BCS–BEC crossover regime.展开更多
基金Supported by the National Natural Science Foundation of China (Grant Nos. 51788104, 11604366, 11774192, and 11634007)the National Key R&D Program of China (Grant Nos. 2017YFA0304600 and 2018YFA0305603)。
文摘Two-dimensional honeycomb crystals have inspired intense research interest for their novel properties and great potential in electronics and optoelectronics. Here, through molecular beam epitaxy on SrTiO_3(001), we report successful epitaxial growth of metal-rich chalcogenide Fe_(2)Te, a honeycomb-structured film that has no direct bulk analogue, under Te-limited growth conditions. The structural morphology and electronic properties of Fe_(2)Te are explored with scanning tunneling microscopy and angle resolved photoemission spectroscopy, which reveal electronic bands cross the Fermi level and nearly flat bands. Moreover, we find a weak interfacial interaction between Fe_(2)Te and the underlying substrates, paving a newly developed alternative avenue for honeycomb-based electronic devices.
基金by the National Natural Science Foundation of China(Grant Nos.62074092 and 11604366)the National Key R&D Program of China(Grant No.2018YFA0305603)。
文摘Unusual quantum phenomena usually emerge upon doping Mott insulators.Using a molecular beam epitaxy system integrated with cryogenic sc√annin√g tunneling microscope,we investigate the electronic structure of a modulation-doped Mott insulator Sn/Si(111)-(√3×√3)R30°.In underdoped regions,we observe a universal pseudogap opening around the Fermi level,which changes little with the applied magnetic field and the occurrence of Sn vacancies.The pseudogap gets smeared out at elevated temperatures and alters in size with the spatial confinement of the Mott insulating phase.Our findings,along with the previously observed superconductivity at a higher doping level,are highly reminiscent of the electronic phase diagram in the doped copper oxide compounds.
基金Supported by the National Key R&D Program of China under Grant Nos 2017YFA0303600,2016YFA0300600 and2016YFA0202300the National Natural Science Foundation of China under Grant No 11634016+3 种基金the Strategic Priority Research Program(B)of Chinese Academy of Sciences under Grant No XDB07030100the Research Program of Beijing Academy of Quantum Information Sciences under Grant No Y18G09the Youth Innovation Promotion Association of Chinese Academy of Sciences under Grant No 2016008the Hundred Talents Program of Chinese Academy of Sciences
文摘In paired Fermi systems,strong many-body effects exhibit in the crossover regime between the Bardeen–Cooper–Schrieffer(BCS)and the Bose–Einstein condensation(BEC)limits.The concept of the BCS–BEC crossover,which is studied intensively in the research field of cold atoms,has been extended to condensed matters.Here by analyzing the typical superconductors within the BCS–BEC phase diagram,we find that FeSe-based superconductors are prone to shift their positions in the BCS–BEC crossover regime by charge doping or substrate substitution,since their Fermi energies and the superconducting gap sizes are comparable.Especially at the interface of single-layer FeSe on SrTiO3 substrate,the superconductivity is relocated closer to the crossover unitary than other doped FeSe-based materials,indicating that the pairing interaction is effectively modulated.We further show that hole-doping can drive the interfacial system into the phase with possible pre-paired electrons,demonstrating its flexible tunability within the BCS–BEC crossover regime.
