Charge density wave without long-range structural modulation in canted antiferromagnetic kagome FeGe
arxiv(2024)
摘要
Strongly correlated electron systems with a kagome lattice can host abundant
exotic quantum states such as superconductivity and spin/charge density waves
(CDW) due to the complicated interactions between different degrees of freedoms
in the framework of a unique two-dimensional geometrically frustrated lattice
structure. Recently, successive orders of A-type antiferromagnetism (AFM),
2×2×2 CDW and canted double-cone AFM have been manifested upon
cooling in magnetic kagome FeGe. However, the mechanism of the CDW order and
its interaction with magnetism are presently enigmatic at best. Here we
investigate the evolution of CDW order with temperature across the spin canting
transition in FeGe by single-crystal x-ray diffraction. Refinements of its
modulated structure are presented using the superspace approach. Interestingly,
the superlattice reflections originating from CDW-induced long-range structural
modulation become extremely weak after the system enters the canted AFM while a
2×2 CDW in the ab plane persists as a long-range order demonstrated by
strong electronic modulation in the dI/dV map of scanning tunneling
spectroscopy. We discovered a novel CDW order without long-range structural
modulation in FeGe probably because of the competition between CDW and canted
AFM in determining the underlying crystal structure. In addition, occupational
modulations of Ge1 atoms located in the kagome plane and displacive modulations
of all the atoms were extracted from the refinements, confirming the existence
of Ge atom dimerization along the c axis as the major distortion and
indicating a dynamic transformation between different CDW domains.
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