B737 Captain reported nose wheel slippage during taxi into gate area. Captain stopped aircraft which was then towed into gate.

Narrative

During the line up on the 1 line; approximately 20 degrees before being strait on the lead in line the nose gear wheel slid on the concrete. The concrete around the gate area appeared wet but not frozen. As soon as the tire lost traction we stopped the airplane and set the parking brake. Ground personnel instructed me to shut down the engine and they would tow us in. The tug hooked up but it also could not get traction either. After locating another tug they were successful in getting us to the gate.