Abstract

Electrical and magnetic properties of underdoped cuprates in the spin gap phase, a precursor to high Tc superconducting state, is riddled with puzzles. We propose a novel reference state to study this phase, where each hole dopant adds one real holon and one real spinon, with Haldane exclusion statistics g_h =1 and g_s = 1/2, to a fairly inert (pseudo gaped) spin liquid vacuum, resulting in a low density spin-charge liquid. Spins and charges interact and form a novel collective state, a 3/2-Fermi liquid. A holon pairs with a spinon; this hole like fermion composite carries charge +e and a spin-\hlf moment and novel exclusion statistics g_{hole} = 3/2. We explain an anomalous expansion of Fermi sea area by 3/2, seen in recent quantum oscillation experiments at two different dopings.