We have a google Authenticator app which generates the 6 digit number for every 30 seconds. My requirement is I need to integrate my Pega application with that google auth. When ever user Enters the Pega url it prompts for user name and password after that user need to input the 6 digit code generated by google Authenticator to access Pega application.
Your use case is just another example of multi-factor authentication - which Pega has made available in 7.3 onwards. Here is a link to a PDN article discussing one approach to using this - from which you can get started in implementing "Google Two-Factor Authentication". There is no current Pega resource for details on this specific approach.