Can we sue for defamation of charachter/slander?

My hubby worked for a company for a year. He was quickly promoted to manager within months. A couple of months ago money went missing from his shift. There are cameras in the establishment and none of which show anything suspicious. My husband and his entire staff were investigated by the local police and the GBI (we live in Georgia). A month later we are in a local store and a former coworker of my hubby's approached and told us all about my hubby's boss blaming mu husband for the money that went missing, saying that she is telling everyone that he works with and everyone that will listen that she believes he did it. My husband and I were outraged but he did nothing because he knows he is innocent and needs a job. Another week goes by and he gets "written up" by his boss for totally made up crap. Another week goes by, another made up write up and a threat to fire him. Finally after 3 more people tell my husband that his boss, THEIR boss is going around telling everyone (even customers) that she thinks he stole the missing money (but never ONCE saying it to my husbands face) he resigns. He was humiliated. He feels like he cannot work in a place were everyone looks at his funny and his boss is thinking he is a crook. It is awful and I feel so bad for him. Can he sue?