Nano-scale Stripe Structures on FeTe Observed by Low-temperature STM/STS

We have investigated the nano-scale stripe structures on a parent compound of the iron chalcogenide superconductor Fe1+dTe (d=0.033) by using low-temperature scanning tunneling microscopy (STM). The STM topographies and the dI/dV maps show clear stripe structures with the period of twice as large as the Te-Te atomic displacement (~0.76 nm = 2a0, a0 is lattice constant), in addition to weak modulation with the same period of lattice constant (~0.38 nm). The bias-voltage dependence of both STM topographies and dI/dV maps show the several kinds of the stripe structures. The 2a0 modulations are similar to the bicollinear spin order of the parent compound FeTe, indicating the possibility of the coupling with spin density wave and electronic structures.