Here's the best way to bet on rising rates

NYSE traders
Adam Jeffery | CNBC

Investors have been waiting for the financial sector to outpace the broad market for some time.

They've been saying that once the big banks get the latest investigation behind them—whether it's for rigging Libor, sketchy foreign exchange trading, etc.—financial stocks will be off to the races.

The biggest bullish thesis is that banks should benefit when interest rates start to increase since the spread between what they have to pay depositors and what they can charge borrowers— known as net interest margin—should increase.