Low-energy interband transitions in the infrared response of Ba(Fe1-xCox)2As2

Maršík, Premysl ; Wang, Chen Nan ; Rössle, Matthias ; Yazdi-Rizi, M. ; Schuster, Roman ; Kim, Kyung Wan ; Dubroka, Adam ; Munzar, Dominik ; Wolf, T. ; Chen, X. H. ; Bernhard, Christian

In: Physical Review B, 2014, vol. 88, no. 18, p. 180508

We studied the doping and temperature (T) dependence of the infrared (IR) response of Ba(Fe1−xCox)2As2 single crystals. We show that a weak band around 1000 cm−1, that was previously interpreted in terms of interaction of the charge carriers with magnetic excitations or of a pseudogap, is rather related to low-energy interband transitions. Specifically, we show that this band exhibits a... More

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    Summary
    We studied the doping and temperature (T) dependence of the infrared (IR) response of Ba(Fe1−xCox)2As2 single crystals. We show that a weak band around 1000 cm−1, that was previously interpreted in terms of interaction of the charge carriers with magnetic excitations or of a pseudogap, is rather related to low-energy interband transitions. Specifically, we show that this band exhibits a similar doping and T dependence as the hole pockets seen by angle resolved photoemission spectroscopy (ARPES). Notably, we find that it vanishes as a function of doping near the critical point where superconductivity is suppressed in the overdoped regime. Our IR data thus provide bulk specific information (complementary to the surface sensitive ARPES) for a Lifshitz transition. Our IR data also reveal a second low-energy band around 2300 cm−1 which further emphasizes the necessity to consider the multiband nature of these iron arsenides in the analysis of the optical response.