Nai Phuan Ong

In 1976 Ong co-discovered (with Pierre Monceau) charge-density-wave (CDW) conduction. 1D metals such as NbSe3 are unstable to the formation of a CDW condensate. If the CDW period is incommensurate with that of the underlying lattice, the condensate was predicted to slide in an applied electric field to carry a current. This was observed in the Ong-Monceau experiment. In 1986, following the Bednorz-Mueller discovery of highTc superconductivity, Ong's group investigated how the Hall effect varies with doping (with Jean-Marie Tarascon). They provided early evidence that the superconducting phase arises by the doping of hole carriers into a parent Mott insulating state. Ong's group proceeded to show that the holes have anomalous properties incompatible with ordinary metals. Ong was awarded the Kamerlingh Onnes Prize (with Uchida and Takagi in 2006). In 2000, Ong's group found that the cuprate pair condensate survives to temperatures high above Tc. The loss of superconductivity at Tc arises from the collapse of phase rigidity rather than the closing of a gap. However, its existence is betrayed by a large Nernst effect and a large orbital diamagnetism. In topological matter, Ong with Bob Cava detected (2010) surface Dirac states in the topological insulator Bi2Te3 by measuring quantum oscillations in a tilted magnetic field. In 2014, Ong and Cava obtained evidence for the predicted "chiral anomaly" in the Dirac semimetals Na3Bi and GdPtBi. In several frustrated quantum magnets, Ong's group has found that spin excitations produce a large thermal Hall current despite being strictly charge-neutral.