PAIRED STATES IN THE EVEN INTEGER QUANTUM HALL-EFFECT

A type of quantum Hall state requiring nonperturbative Landau-level mi xing is argued to arise at low electron density. In these states, up- and down-spin electrons pair to form spinless bosons that condense int o a bosonic quantum Hall state. We show that a BCS instability arising in two-component Hall metals stabilizes this paired state at nu=2. We discuss various experimental implications including a new global phas e diagram for the integral quantum Hall effect with spin.