Photolibrary trash bin

Photos.app has a default library. Usually in ~/Pictures, if it hasn't been moved. Assuming you moved your 'photolibrary' file to the trash. So now the Photos.app is recreating the folder structure whenever it - or it's background utility programs that ensure the app is functioning properly - are started. Similar to when you reboot your system.

If you empty the trash and then start the Photos.app. Does the folder return? If so, follow the instructions below.

Start the Photos.app while holding the 'Option' key to get a dialog that allows you to create a new library somewhere else. Set that new one as default. Then delete what's left in the trash. It should be gone for good.

If you deleted the photos library from an external drive, reconnect that external drive and empty the trash bin again