Jewook Part - Oak Ridge National Laboratory

Wednesday Oct 28, 2026, 9:00 AM → 8:15 PM US/Eastern

IAMM

Jewook is a R&D Staff in the Center for Nanophase Materials Science at the Oak Ridge National Laboratory. He is interested in exploring quantum matter in atomic scale. He exploits scanning tunneling microscopy and spectroscopy (STM/S) to characterize structural, electrical, magnetic, and thermal properties that emergent at the low-dimensional interfaces. 

9:00 AM → 10:00 AM Arrive at IAMM

Speaker: Wonhee Ko (University of Tennessee, Knoxville)

10:00 AM → 10:20 AM Talk Prep

10:20 AM → 11:20 AM Deciphering Majorana Zero Modes in FeTe$_{0.55}$Se$_{0.45}$: Millikelvin Scanning Tunneling Spectroscopy and Machine-Learning-Assisted Analysis

Unambiguous identification of Majorana zero modes in topological superconductors remains a challenge due to complex in-gap states that can also produce zero-bias conductance peaks. Here we present a data-driven workflow that combines pixel-wise spectral deconvolution with machine learning to analyze tunneling spectroscopy from FeTe$_{0.55}$Se$_{0.45}$, an intrinsic topological superconductor. We acquired spatially resolved local density of states spectra using a millikelvin scanning tunneling microscope under magnetic fields and decomposed each spectrum into multiple Lorentzian peaks. The resulting peak parameters were then analyzed using unsupervised dimensionality reduction and clustering. This analysis identified distinct pixelwise spectra within the vortices, allowing us to distinguish vortices with zero-bias peaks consistent with established Majorana signatures from those with similar peaks that may have a trivial origin. Spatial maps of the zero-bias-peak distributions further revealed isotropic vortex cores with well-defined zero-bias peaks from vortices with locally distorted peaks. Comparison with defect locations measured in zero magnetic field revealed a correlation between local heterogeneity and zero-bias-peak formation. This objective and reproducible workflow advances the reliable identification of potential Majorana signatures from complex in-gap states and advances reliable studies of Majorana zero modes in topological superconductors.

11:30 AM → 12:00 PM Research Meeting

Speaker: Prof. Adrian Del Maestro (University of Tennessee, Knoxville)

12:00 PM → 2:00 PM Lunch

Wonhee Ko, Joon Sue Lee ...

2:00 PM → 2:30 PM Research Meeting

2:30 PM → 3:00 PM Research Meeting

3:00 PM → 3:30 PM Research Meeting

3:30 PM → 4:00 PM Research Meeting

4:00 PM → 4:30 PM Research meeting

5:30 PM → 7:00 PM Dinner