Chiral charge order from interlayer tunneling in the hole doped cuprates

We show how charge density waves in layered materials can be gyrotropic, {\it i.e.} break spatial inversion and all mirror symmetries. This order is stabilized by coherent interlayer tunneling whose amplitude depends on in-plane momentum. We present mean field calculations which demonstrate the presence of this chiral configuration of charge density waves, and justify these results using a Landau-Ginzburg theory. The implications for recent experiments ({\it e.g.} Kerr, X-ray etc.) in underdoped YBCO are also discussed.