  We find the first example of a quantum Berenzinskii-Kosterlitz-Thouless (BKT)
phase transition in two spatial dimensions via holography. This transition
occurs in the D3/D5 system at nonzero density and magnetic field. At any
nonzero temperature, the BKT scaling is destroyed and the transition becomes
second order with mean-field exponents. We go on to conjecture about the
generality of quantum BKT transitions in two spatial dimensions.
