Mobile payments startup Square vaulted higher in its Wall Street debut Thursday a day after a hefty markdown of its public offering price amid concerns over tech valuations.

At 1600 GMT, Square had surged 52 percent to $13.66.

"We're really excited to go back to work. We have a real idea of what needs to be done," said Square chief Jack Dorsey on CNBC after ringing the New York Stock Exchange opening bell.

"It's all about accelerating the business now, our tools and our features."

The mobile payments on Wednesday priced its shares at $9 -- discounted from the original range of $11 to $13 and a huge markdown from the valuation assigned by early private equity investors.

The IPO raised $243 million, and gave Square a market value of $3 billion -- or roughly half the level from its latest private funding round.

Some analysts have warned of a tech bubble in the private markets, with dozens of firms getting a value of over $1 billion -- "unicorns" in Silicon Valley parlance -- without enough scrutiny over their financial prospects.

The research firm PrivCo said Square's debut "will set a precedent with regard to how investors react to unicorns in the public market."