I was trying a similar approach to google which login in 1 page and password in the second but a coworker said that for accessibility reasons password and login should be in one screen. Is there any science-based evidence for this?
This seems to be a heated debate but here is Google's official explanation regarding why they separated username/password onto different pages for Gmail:
This new Google account sign-in flow will provide the following advantages:
- Preparation for future authentication solutions that complement passwords
- Reduced confusion among people who have multiple Google accounts
- A better experience for SAML SSO users, such as university students or corporate users that sign in with a different identity provider than Google
I could see separating UN/PW across different pages having security advantages, e.g., the system could theoretically offer more personalized security authentication (based on the email entered, offer an image or phrase specific to that email/user), then ask for password. But, no doubt, this security technique wouldn't be foolproof.
See this Ghacks article for more on this subject.
From a UX/usability standpoint, having the UN/PW on one page would likely be faster for the user, of course. Usability vs. security; there are always trade-offs to make. ;)