Engineering Emergent Correlated States with Complex Quantum Materials  New electronic states often emerge at atomically clean interfaces between parent states hosted indistinct crystalline lattices. Yet some of the most interesting strongly correlated parent states exist only in complex materials which easily degrade.
In this talk, I demonstrate two different strategies for realizing emergent correlated electronic states by design. First, using a novel cryogenic van der Waals stacking technique, we created twist Josephson junctions between high temperature Bi2Sr2CaCu2O8+x superconductors with quality approaching that between CuO2 layers of single crystals. At 45 degree twist angle, we observe half-integer Shapiro steps and spontaneous time-reversal symmetry breaking, consistent with the emergence of predicted interfacial high-temperature topological superconductivity. Next, I discuss our discovery of the single-crystal superconductor BaTa2S5, whose superlattice of weakly coupled H-TaS2 monolayers achieve high electronic mobility while breaking inversion symmetry of the parent 2H-TaS2 compound. Using multiple independent experimental probes, we uncover a magnetic field induced phase transition between distinct superconducting states, one of which survives well beyond 59 T, at least 12 times the Pauli limit. This phase boundary intersects the superconducting-normal boundary exactly at an upturn in HC2(T), pointing to the emergence of field-induced spin-triplet superconductivity.Â
  Refreshments - 1:30 pm at 1117 Toll Physics Bldg.