If the TV and the receiver both support ARC (audio return channel), then you don't need any other hardware. Supposedly, that is. I have no idea if there's any add-on hardware you can use to "fake" an ARC connection to use just the HDMI cable.
My LG TV and Marantz receiver both have ARC, but it doesn't work because of some really weird engineering decisions in the LG TV. If I'm watching OTA programming on the LG, then ARC works and I get the audio back to the receiver. If I'm watching a "Smart TV" app (like Netflix) on the LG, then the audio is NOT sent to the receiver via ARC. I'm not sure what the LG people were smoking the day they thought that was an acceptable decision. So in my case, I had to connect an optical audio cable from the TV back to the receiver.