This summer, the Meta chief executive, Mark Zuckerberg, invited Rishabh Agarwal to join the company’s new A.I. lab, offering him millions of dollars in stock and salary.

With the new lab, Mr. Zuckerberg said he wanted to build “superintelligence,” a technology that could eclipse the powers of the human brain. Though no one knew how to create superintelligence, he urged Dr. Agarwal to make a leap of faith.

In a world that is changing fast, Mr. Zuckerberg told him, the biggest risk you can take is not taking any risk.

But although Dr. Agarwal was already a Meta employee, he turned down the offer to join another company.

Dr. Agarwal is among more than 20 researchers who have left their work at Meta, OpenAI, Google DeepMind and other big A.I. projects in recent weeks to join a new Silicon Valley start-up called Periodic Labs. Many of them have given up tens of millions of dollars — if not hundreds of millions — to make the move.

As the A.I. labs chase amorphous goals like superintelligence and a similar concept called artificial general intelligence, Periodic is focused on building A.I technology that can accelerate new scientific discoveries in areas like physics and chemistry.