This facility doesn't exist directly within the search facility. The best I could come up with is 

>[tag] created:YYYY-MM-DD answers:N

so something like

>[\[linux\] created:2014-03-07 answers:0][1]

Will get you close but remember that SE's definition of unanswered means that a question has no _upvoted_ answers so this will be different from the unanswered tab.

  [1]: http://serverfault.com/search?q=%5Blinux%5D%20created:2014-03-07%20answers:0