One Direction's "Take Me Home" is the taking the boys to the top of the charts - and to new heights.

The group's sophomore album has sold 540,000 in its first week, according to Nielsen SoundScan. It's the year's third-highest debut behind Taylor Swift's "Red," which sold 1.2 million units its first week earlier this month, and Mumford & Sons' "Babel," which sold more than 600,000 albums in September in its debut week.

"We just want to say a massive thanks to all the fans who have supported us," band member Harry Styles, 18, said in an interview Tuesday from London. "We can send tweets and thank them, but 140 characters is never going be enough to say how much it means."

The album also debuted at No. 1 in the United Kingdom this week and is No. 1 in more than 30 countries, Columbia Records said Wednesday. The fivesome's debut, "Up All Night," came in at No. 2 in the United Kingdom last year; it was just released in March in America, where it hit No. 1 and has achieved platinum status.

"We were a little bit nervous about how people were going to take it," 19-year-old Niall Horan said of the new album during tour rehearsals. "Everyone gets that second album syndrome."

They say though they're excited, they won't be celebrating too much: "We're finishing rehearsing soon and we're going home to bed."

One Direction, who placed third on the UK version of "The X Factor" in 2010, is signed to Simon Cowell's Syco label imprint. In just a year, the band has become worldwide sensations, thanks to its feverish fans. They released a book and have a 3D movie planned. They also made the cut for Barbara Walters' most fascinating people of 2012 list, which includes New Jersey Gov. Chris Christie and US gold medalist Gabby Douglas.

One Direction says those experiences have helped the group mature.

"We've been working hard. We're starting to grow up," Horan said. "We're still young, but we've passed the initial teenage years. ...We've grown up quite quick in the job we have to do and we became a lot more independent."

The group - which includes Zayn Malik, Liam Payne and Louis Tomlinson - will launch a worldwide tour in February. They hope to work with Katy Perry and are still trying to adjust to the celebrity and fame that has taken over their lives.

"I can see how it gets to people. I guess it's quite easy to get wrapped up in it all," Styles said. "We do the same things every other lad our age does. We go out, we have fun, we meet girls and stuff like that. Sometimes it gets written about, which, yeah, we think about it and it's absolutely crazy. It's still a bit weird thinking that that's the way it is."