On Tuesday, Cillian Murphy was at his parents’ home in Cork, Ireland, drinking a cup of tea when his phone started buzzing. A glance at the dozens of texts revealed the news: For the first time, Murphy had been nominated for the best actor Oscar, for his performance as the title character in “Oppenheimer.”“It’s very, very humbling,” Murphy, 48, said in an interview by phone on Tuesday. “I’m kind of a little in shock.”“It’s just a real honor to be involved in a film that has connected so powerfully with people in a way that we never expected,” he added.In “Oppenheimer,” a stunning biopic by the director Christopher Nolan, Murphy plays the American theoretical physicist J. Robert Oppenheimer, a brilliant, enigmatic figure known as the father of the atomic bomb, a man consumed with ambition and haunted by his past. After opening alongside “Barbie” on July 21, “Oppenheimer” quickly became beloved by critics and fans alike, grossing just over $950 million at the worldwide box office.Murphy had collaborated with Nolan before, taking supporting roles in movies like “Batman Begins” and “Inception,” but his latest work for the director became a breakthrough moment, with Murphy winning praise for the intensity and emotional complexity he brought to the role. At the Golden Globes, he won best actor in a drama; he also was up for a Critic’s Choice Award (losing out to his fellow Oscar nominee Paul Giamatti); and he’s in the running for a Screen Actors Guild Award, punctuating what has been an exceptionally busy awards season for Murphy.“It’s been new enough for me, but I gotta say, I think I’m getting good at it,” he said, chuckling. He marveled about a recent ceremony where he was stuck in a line with Meryl Streep.“That may never happen to me again in my life, and it’s just a wonderful feeling,” he said.In a phone interview, Murphy also discussed what fascinated him about Oppenheimer the man, how he prepared for the role and the cast’s group chat. These are edited excerpts from the conversation.Were you watching the Oscars announcement?No, I was at home in Cork with my mom and dad and my wife. And my phone started popping, so I figured it was good news. Everybody started texting. You know, you can’t really avoid good news or bad news, but it’s better when it’s good news.Oppenheimer is a different role than what you’ve done in the past. What drew you to this character?Well, he is, in Chris’s words, the most important man that ever lived. He changed the course of the 20th century, and we are all living in Oppenheimer’s world. He was complex and contradictory and flawed and vain and arrogant, but he was still immensely charismatic and fascinating. It was a huge responsibility. But the sorts of roles I enjoy are the ones where you think, I have no idea how I’m going to play this.Murphy said his phone blew up with word of his Oscar nomination. “You know, you can’t really avoid good news or bad news, but it’s better when it’s good news.”Melinda Sue Gordon/Universal PicturesWhat steps did you take to prepare?Oh man, I had six months. From the moment Chris called me, I just started working — from the inside out and from the outside in. I did an awful lot of reading and research and watched every single archival footage about him. Then I immediately started conditioning my body because he was very interesting how he carried himself physically and how slight his frame was. But a lot of it was just walking around my basement in Dublin talking to myself and practicing, practicing and practicing.As you did that research, was there anything surprising to you about Oppenheimer?He was an absolute contradiction in so many ways. He could have been an artist or a writer or a poet. But he was also this freakishly bright human being. A lot of his contemporaries would say he was the brightest man in the room at all times. But he was also very temperamental and fragile emotionally and mentally, particularly in his youth. If you were writing a fictional character, it wouldn’t add up to a character people could identify with. But in fact, he was just like the rest of us. He was just a human being. So that’s what I really identified with — his humanity.What was it like for you to work with such an all-star cast?A total gift. Every single cast member was fearless in the film, like they had done so much research and could improvise on the spot about their character and the real-life events. I felt really held and carried by everybody on the movie. We’re still all really close. There was a really good bond on this film, and it remains very very strong.Is it true there’s an “Oppenhomies” group chat?That is true, yes. Olivia Thirlby came up with that moniker.You and Nolan have a long history of working together. How did that impact your work with this film?Oh, it’s crucial for me. I don’t think I could have made this film with anyone else, without that level of trust that goes back six movies and 20 years. He really, really pushed me and I wanted to be pushed. He expects excellence from you because that’s what he delivers himself every single day.Is there something distinctive about a Nolan set or film that’s different from other projects you’ve been involved in?I think it’s the level of focus. It’s quite remarkable. It’s laserlike, the way he uses time, because time, I’ve realized, is your most valuable commodity when you’re on a film set. So much of it gets wasted. When you come on a Chris Nolan set, you come on to work. There’s no phones, there’s no chatting. There’s no video footage, there’s no monitors. That’s not to say it’s not a pleasant environment. It’s a private, focused environment. That’s how you get the best out of people.In terms of time, you didn’t have much of that at all right?No, we filmed in 57 days, and three of them were a preshoot. So it was insane, the pace of it, but it never felt rushed. We never left a scene behind.Some people have criticized the film for the inclusion of nude scenes. What do you make of that critique?Well, I think those things are essential for the story. If you’re familiar with the story, it was his relationship with Jean Tatlock which was the thing that really made him lose his security clearance and ultimately kind of cost his career. I think it was vital to highlight the intimacy and closeness of their relationship.Besides the Academy Awards ceremony, what else is in the future for you?I have a film called “Small Things Like These,” which I produced and acted in and that’s opening at the Berlin Film Festival in February. I’m really proud of the movie. It’s produced by Matt Damon and Ben Affleck. They paid for it and we produced it together. So I’m juggling that and attending all these events at the same time. More