https://scholar.dgist.ac.kr/handle/20.500.11750/800 2026-04-06T15:29:00Z 2026-04-06T15:29:00Z An, Sung Jin Kim, Jisu Jung, Myung-chul Park, Kidong Park, Jeunghee Shim, Seung-bo Kim, Hakseong Siu, Zhuo Bin Jalil, Mansoor B.A. Schönenberger, Christian Myoung, Nojoon Seo, Jungpil Jung, Minkyung https://scholar.dgist.ac.kr/handle/20.500.11750/59294 2025-12-30T09:10:13Z 2025-09-30T15:00:00Z

Title: Radio-Frequency Detection of Fabry–Pérot Interference and Quantum Capacitance in Long-Channel Three-Dimensional Dirac Semimetal Cd3As2Nanowires Author(s): An, Sung Jin; Kim, Jisu; Jung, Myung-chul; Park, Kidong; Park, Jeunghee; Shim, Seung-bo; Kim, Hakseong; Siu, Zhuo Bin; Jalil, Mansoor B.A.; Schönenberger, Christian; Myoung, Nojoon; Seo, Jungpil; Jung, Minkyung Abstract: We demonstrate phase-coherent transport in suspended long-channel Cd3As2 nanowire devices using both direct current (DC) transport and radiofrequency (RF) reflectometry measurements. By integrating Cd3As2 nanowires with on-chip superconducting LC resonators, we achieve sensitive detection of both resistance and quantum capacitance variations. In a long-channel device (L ≈ 1.8 μm), clear Fabry–Pérot (FP) interference patterns are observed in both DC and RF measurements, providing strong evidence for ballistic electron transport. RF reflectometry reveals gate-dependent modulations of the resonance frequency arising from quantum capacitance oscillations induced by changes in the density of states and FP interference. These oscillations exhibit a quasi-periodic structure that closely correlates with the FP patterns in DC transport measurements. In another device of a Cd3As2 nanowire Josephson junction (L ≈ 730 nm, superconducting Al contacts), FP interference patterns are too weak to be resolved in DC conductance but are detectable using RF reflectometry. These results demonstrate the high quality of our Cd3As2 nanowires and the versatility of RF reflectometry, establishing their potential for applications in topological quantum devices such as Andreev qubits or gatemon architectures.

2025-09-30T15:00:00Z Park, Jaemun Kim, Woo-Yong Cho, Beopgil Choi, Woojae Kwon, Yong Seung Seo, Jungpil Park, Keeseong https://scholar.dgist.ac.kr/handle/20.500.11750/58375 2025-12-18T02:41:42Z 2025-05-31T15:00:00Z

Title: Nominal Kagome Antiferromagnetic Mn3Sn: Effects of excess Mn and its novel synthesis method Author(s): Park, Jaemun; Kim, Woo-Yong; Cho, Beopgil; Choi, Woojae; Kwon, Yong Seung; Seo, Jungpil; Park, Keeseong Abstract: The antiferromagnetic (AFM) Weyl semimetal Mn3Sn has attracted significant interest due to its intriguing topological and transport properties. However, the reproducibility of experimental results has been limited, potentially stemming from the thermodynamically stable Mn3+xSn1-x phase, where excess Mn substitutes at Sn sites and alters its intrinsic helical ordering. In this study, we present a Bi flux-assisted recrystallization method for synthesizing high-quality nominal Mn3Sn single crystals. Our approach yields stoichiometric and homogeneous samples with the largest residual resistivity ratio (RRR > 23) and sharper magnetic phase transitions, confirming their high purity. While the triangular AFM phase at room temperature is independent of sample quality, the helical magnetic ordering exhibits strong quality dependence, with additional helical phases emerging between 250 K and 280 K. At low temperatures, the system retains a semimetallic nature, as evidenced by the lower Sommerfeld coefficient (gamma), differential conductance (dI/dV) spectra, and magnetoresistance measurements. These findings highlight the interplay between chemical composition and magnetic phase transitions in Mn3Sn and establish a direct link between its helical ordering and electronic structure tuning. Our results not only provide a pathway for producing high-quality Mn3Sn single crystals but also offer a valuable platform for exploring unresolved aspects of its helical phases and potential applications in AFM spintronics.

2025-05-31T15:00:00Z Lee, Si-Hong Kim, Youngjae Cho, Beopgil Park, Jaemun Kim, Min-Seok Park, Kidong Jeon, Hoyeon Jung, Minkyung Park, Keeseong Lee, JaeDong Seo, Jungpil https://scholar.dgist.ac.kr/handle/20.500.11750/17148 2025-07-25T02:38:30Z 2022-08-31T15:00:00Z

Title: Spin-polarized and possible pseudospin-polarized scanning tunneling microscopy in kagome metal FeSn Author(s): Lee, Si-Hong; Kim, Youngjae; Cho, Beopgil; Park, Jaemun; Kim, Min-Seok; Park, Kidong; Jeon, Hoyeon; Jung, Minkyung; Park, Keeseong; Lee, JaeDong; Seo, Jungpil Abstract: Kagome Lattices provide a platform for studying competing quantum ground states. Lee and colleagues observed the pseudospin texture of FeSn in real space, deepening our understanding of the lattice symmetry-preserving tunneling process in Dirac materials. A kagome lattice (KL) is a two-dimensional atomic network comprising hexagons interspersed with triangles, which provides a fascinating platform for studying competing quantum ground states. The KL contains three atoms in a unit cell, and their degrees of freedom combine to yield Dirac bands and a flat band. Despite many studies to understand the flat band in KL, exploring the pseudospin of Dirac bands in KL has been scarce. In this paper, we suggest pseudospin-polarized scanning tunneling microscopy that is analogous to spin-polarized scanning tunneling microscopy. Using a pseudospin-polarized tip, we possibly observed the pseudospin texture of kagome metal FeSn in real space. Based on a simple tight-binding calculation, we further simulated the pseudospin texture of KL, confirming the geometric origin of pseudospin. This work potentially deepens our understanding of the lattice symmetry-preserving tunneling process in Dirac materials.

2022-08-31T15:00:00Z Song, Sang Yong Park, Yun Sung Jeong, Yongchan Kim, Min-Seok Kim, Ki-Seok Seo, Jungpil https://scholar.dgist.ac.kr/handle/20.500.11750/15430 2025-07-25T03:33:17Z 2021-05-31T15:00:00Z

Title: Yu-Shiba-Rusinov bound states studied by tuning the electron density at the Fermi energy Author(s): Song, Sang Yong; Park, Yun Sung; Jeong, Yongchan; Kim, Min-Seok; Kim, Ki-Seok; Seo, Jungpil Abstract: We studied the nature of Yu-Shiba-Rusinov (YSR) bound states in response to the potential scattering U by tuning the electron density at the Fermi energy. By comparing two systems, Mn-phthalocyanine molecules on Pb(111) and Co atoms on PbSe/Pb(111), we demonstrate that the sign of U can be unambiguously determined by varying the electron density at the Fermi energy. We further show that U competes with the exchange interaction JS in the formation of YSR bound states. Our work provides insights into the interactions between magnetic atoms and superconductors at a fundamental level. © 2021 American Physical Society.

2021-05-31T15:00:00Z