Ph.D. candidate publishing preprint to link papers
In general, you can post the preprints version of the paper before submitting if the journals do not have a policy which require you not to publish the preprint on repositories like arxiv, vixra, etc. See for example International Journal of Modern Physics D, where they have a policy of embargo which is explained. From this link you can see the author rights "After an embargo of 12 months, you may post the accepted author manuscript on your personal website, your institutional or subject repositories of your own choice or as stipulated by the Funding Agency. 
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To be clear, when you publish on arxiv, you give the an irrevocable license to distribute the article to arxiv, which means that you cannot withdraw the paper from arxiv unless there is a crucial mistake on it (see here ).

Here you can see the policies for many journals, for example
"Author's Pre-print:    green tick  author can archive pre-print (ie pre-refereeing)
Author's Post-print:    green tick  author can archive post-print (ie final draft post-refereeing)
Publisher's Version/PDF:    green tick  author can archive publisher's version/PDF
General Conditions: 
On author's personal website, employer's website or institutional repository
Publisher's version/PDF may be used
Publisher's version/PDF may be used on author's personal website or employer's website only
Link to publisher version required
Publisher copyright and source must be acknowledged with citation"

Finally, you need to check with the policy of the journal where you have submitted the 2 papers, and if you cannot publish on arxiv, you can cite with something like "_authors, paper name, submitted". 

In the present, the world will go to open access, and we as authors have to encourage these movements and to publish the preprints online on free repositories.