Electronic nematicity, interface ferroelectricity, and superfluid stiffness in superconducting LaAlO3/KTO3

ABSTRACT

The LaAlO3/KTO3(111) heterointerface hosts superconductivity and a wealth of emergent phenomena. Using the angle-resolved resistivity (ARR) method, we systematically probed electronic nematicity in both the normal state and the superconducting fluctuating state, providing evidence for nematic superconductivity and nematic quantum metal state. We also uncovered ferroelectric order at the interface, where two seemingly mutually exclusive orders—ferroelectricity and superconductivity—coexist. Ferroelectricity was established through scanning transmission electron microscopy (STEM), second harmonic generation (SHG) microscopy, and piezoelectric force microscopy (PFM). The ferroelectric polarization is locally switchable, driving changes in interfacial conductivity by more than 1000 times while simultaneously suppressing superconductivity. By developing a sensitive two-coil mutual inductance technique compatible with a dilution refrigerator, we measured the superfluid stiffness and found a remarkable BEC-like to BCS-like crossover. Together, these findings reveal the rich yet intricate physics of oxide interfaces.

 

BIOGRAPHY

Prof. Jie Wu received his Bachelor’s and Master’s degrees from Fudan University in year 2001 and 2004, respectively, and his Ph. D. in experimental condensed matter physics from the University of California at Berkeley in 2010. From 2010 to 2012, he conducted postdoctoral research at the National High Magnetic Field Laboratory of United States. In 2012, he was appointed Assistant Physicist at Brookhaven National Laboratory, where he was promoted to Associate Physicist in 2014, and to Physicist in 2017. Since September 2019, he has been a faculty member of Westlake University.

Prof. Wu leads a quantum materials research group at Westlake University, focusing on oxide molecular beam epitaxy and low temperature transport measurements of unconventional superconductivity and magnetism. He has published more than 60 papers in peer-reviewed journals, including Nature, Science, Nature Materials, etc. He is currently the chair of Physics Department of Westlake University.