Applications for a position in the group are welcome at all times.
Applications for postdoc positions should be submitted through the visitors program: https://www.pks.mpg.de/visitors-program/application/
Send your CV and a brief motivation to the group leader.
You also have the possibility to apply through the IMPRS: http://www.imprs-mpsse.mpg.de/application/general-information/
The condensed matter division and associated groups normally have a call in autumn: https://www.pks.mpg.de/mpi-doc/CondensedMatter//media/documents/SummerInternship_18.pdf
Contact the group leader for more information.