Does a husband need a power of attorney over his deceased wife to access bank, retirement benefits at work and social security?

Power of attorney dies with the person granting the power. Husband will need to be appointed personal representative of the wife's estate, or if the accounts are joint or he is the beneficiary he will alert the bank, etc. and present an original copy of the death certificate to gain access. Contact each institution and find out what they require. If you need help please find an Estate Planning Attorney in your area, they handle probate all of the time and can get the accounts processed efficiently.