If you are a citizen of a member state of the European Union (EU), the European Economic Area (EEA) or Switzerland, you do not need a visa to enter the territories of the other member-states. If the period of your PhD studies, your research or your work as a highly-skilled professional is more than three months, you need to address the authorities for administrative control of foreigners in the respective country in order to obtain a residence permit.
It is advisable that the members of your family and you possess an European Health Insurance Card or its equivalent (a provisional replacement certificate) for the period of your temporary stay in another member state. This document facilitates your access to medical treatment that you may need during the period of your stay.
If you are a Bulgarian citizen or you are residing on the territory of Bulgaria and you are going to study as a PhD student, carry out research or work as a highly-skilled professional in countries outside EU/EEA and Switzerland, you may obtain more detailed information and assistance from the diplomatic and consular missions of the respective country in the Republic of Bulgaria.