After already reaping notice for his performance in “ Her ,” Joaquin Phoenix could be working with Warner Bros. again on the studio’s biggest property.Sources tell Variety that the studio wants the Oscar-winning actor for a role in the upcoming untitled Batman-Superman pic. However, it’s very early in the process and even if Warners offers Phoenix a role, it’s not clear he would accept as the actor has steered clear of big-budget pics in the past few years, leaning towards movies with a more prestige feel.Phoenix is also weighing an offer on the Gus Van Sant pic “Sea of Trees” and is believed to still be considering that offer as well.WB and the actor’s reps had no comment.Though sources couldn’t confirm what the role is, it’s believed to be for the main antagonist, which is likely to be Lex Luthor. Names like