"Quantum Devices with Quantum Materials" by Mr. Yun-Yi Pai

"Quantum Devices with Quantum Materials"

Mr. Yun-Yi Pai, Department of Physics and Astronomy, University of Pittsburgh

One-Dimensional Nature of Superconductivity at the LaAlO₃/SrTiO₃ Interface

The superconductivity of SrTiO₃ has remained puzzling for over half of a century [1]. This material is notorious for its coupled degree of freedoms from polar, octahedra rotation, charge, orbital, defect, and magnetism. Thanks to the discovery of LaAlO₃/SrTiO₃ interface to reduce the dimensionality of the mobile electronic system from 3D to 2D [2], and c-AFM lithography to reduce further from 2D to 1D and 0D [3], physics that were not otherwise observable were now found. For example, electron pairing far outside of the superconducting state was finally observed [4] after being proposed in the 60s by Eagles [5].  The electrons exhibit a series of 1-, 2-, 3-, 4-, 5- electron bound states that were not foreseen before [6]. Here, with the same technique, we carefully examine the dimensionality of the superconductivity at the LaAlO₃/SrTiO₃ Interface.  Evident 1D nature of the superconductivity was observed [7].  The observation imposes strong constraints on the possible pairing mechanism.

About the speaker: Yun-Yi Pai earned his M.S. degree from Fuchs group in Department of Applied and Engineering Physics at Cornell University in 2014 on characterization of single photon source in zinc oxide.  Afterwards, he joined Levy group in Department of Physics and Astronomy at University of Pittsburgh for his Ph.D. His focus is on mesoscopic devices created at complex oxide heterointerface LaAlO₃/SrTiO₃ and scanning probe at milliKelvin temperatures.  In 2019 He visited Long-Qing Chen group at Penn State University on phase-field modeling SrTiO₃. He is currently a predoctoral intern at Oak Ridge National Laboratory, working on optical characterization of LaAlO₃/SrTiO₃ at milliKelvin temperatures.