revtex4-1 document class automatically loads the
natbib package with the option
sort&compress. For numerical citation methods, this ensures that an otherwise wild-looking list such as
[4,2,8,3] will be rendered as
[2-4,8]; for author-year citation methods, this option is equivalent to (simple) sorting by year (and, if necessary, within year by affixing
If the journal you're submitting your paper to does not want the bibliography to be sorted alphabetically by authors' last names, it should also specify which bibliography style file should be used. If the journal for some reason has failed to do so, you should select a style file --
unsrtnat.bst would be a good candidate, given that you're likely using
natbib's citation commands -- that does not perform any sorting of the bib entries. Incidentally, after selecting a new style file, it may be necessary to wipe out the auxiliary files and perform the latex-bibtex-latex-latex sequence from scratch.
A separate issue: have you been able to determine which basic citation method is required by the journal: numeric or authoryear? If it's the former, you should include the instruction
in the preamble. If it's the latter, you may want to play it safe by including the instruction
in the preamble. This is actually the default when
natbib is set up. However, it may be the case that some of the other files you're loading override this default, in which case it may be necessary to restore the default setting explicitly.