https://scholar.dgist.ac.kr/handle/20.500.11750/800 2026-11-11T11:27:15Z 2026-11-11T11:27:15Z Qian, Yuting Kim, Younsik Kim, Du Hyung Oh, Taekoo Hwang, Yoonseok Kyung, Wonshik Yoo, Junseo Kim, Sehoon Lee, Suyoung Song, Hyunjee Kim, Mi Kyung Cheng, Cheng-Maw Kim, Min-Seok Park, Se Young Yue, Changming Seo, Jungpil Kim, Changyoung Yang, Bohm-Jung https://scholar.dgist.ac.kr/handle/20.500.11750/61110 2026-11-06T08:40:13Z 2026-05-31T15:00:00Z

Title: Correlated singular flat bands on the surface pentagonal lattice of ferromagnetic CoS2 Author(s): Qian, Yuting; Kim, Younsik; Kim, Du Hyung; Oh, Taekoo; Hwang, Yoonseok; Kyung, Wonshik; Yoo, Junseo; Kim, Sehoon; Lee, Suyoung; Song, Hyunjee; Kim, Mi Kyung; Cheng, Cheng-Maw; Kim, Min-Seok; Park, Se Young; Yue, Changming; Seo, Jungpil; Kim, Changyoung; Yang, Bohm-Jung Abstract: Flat bands have been proposed in various geometrically frustrated lattices, yet their experimental realization has been limited only to the two-dimensional (2D) kagome and three-dimensional (3D) pyrochlore lattices. While synthesizing bulk crystals with desired lattice geometry is generally challenging, the surfaces of 3D bulk materials sometimes naturally host 2D lattice structures hardly achievable in 2D bulk crystals. Thus, the electrons localized on such 2D surfaces can be a new platform for exotic flat bands residing on the unexplored lattice geometry. Here, we report the first experimental observation of singular flat bands with band crossings in the 2D pentagonal lattice on the surface of the 3D ferromagnetic topological semimetal CoS2. We demonstrate that the coupling between localized surface flat bands and extended bulk topological bands gives rise to the surface non-Fermi liquid behavior characterized by the quasiparticle scattering rate with linear temperature dependence and pronounced quasiparticle broadening. This study of CoS2 highlights metallic pyrite materials as an ideal platform for exploring the exotic properties of spin-polarized singular flat bands localized on the surface pentagonal lattice, which provides a fresh perspective for investigating correlated electron phenomena in pentagon-based materials.

2026-05-31T15:00:00Z Kim, Bomin Jeong, Yunseong Baek, Wonjung Kim, Hobyeong 이태성 Cho, Beopgil Choi, Woojae Ha, Jae-Hyun Park, Jaemun Hong, Jung-Il Kwon, Yong Seung Seo, Jungpil Park, Keeseong https://scholar.dgist.ac.kr/handle/20.500.11750/60590 2026-11-11T05:40:23Z 2026-07-31T15:00:00Z

Title: A comparative synthesis study of α-MnTe across solid-state, Arc-melting, and Te-flux routes Author(s): Kim, Bomin; Jeong, Yunseong; Baek, Wonjung; Kim, Hobyeong; 이태성; Cho, Beopgil; Choi, Woojae; Ha, Jae-Hyun; Park, Jaemun; Hong, Jung-Il; Kwon, Yong Seung; Seo, Jungpil; Park, Keeseong Abstract: Although alpha-MnTe has attracted renewed interest in both thermoelectric and altermagnetic contexts, direct comparisons of practically accessible synthesis routes within a common experimental framework remain limited. Here, we compare conventional solid-state reaction, arc melting and Te self-flux growth methods under a common framework of composition control and thermal history. Within the explored conditions, the phase outcome depends not only on the nominal starting composition but also on route-dependent synthesis environments, including volatilization in sealed ampoules, repeated remelting and rapid quenching in arc melting, and crystal-flux interfacial segregation in Te self-flux growth. In the solid-state route, slow heating with a slightly Mn-rich starting composition was associated with reduced MnTe2 and alpha-MnTe-dominant products. Arc melting yielded alpha-MnTe-dominant products without post-annealing, accompanied by dendritic-like microstructures. Te self-flux growth yielded single crystals, although a minor MnTe2-rich interfacial or surface layer often remained. While the present dataset does not define a rigorous phase boundary or a definitive mechanistic model, it provides a systematic comparative framework for route-dependent phase outcomes and impurity persistence in alpha-MnTe synthesis.

2026-07-31T15:00:00Z Kim, Bomin Jeong, Yunseong Baek, Wonjung Kim, Hobyeong 이태성 Cho, Beopgil Choi, Woojae Ha, Jae-Hyun Park, Jaemun Hong, Jung-Il Kwon, Yong Seung Seo, Jungpil Park, Keeseong https://scholar.dgist.ac.kr/handle/20.500.11750/60502 2026-11-11T05:40:23Z 2026-07-31T15:00:00Z

Title: A comparative synthesis study of α-MnTe across solid-state, Arc-melting, and Te-flux routes Author(s): Kim, Bomin; Jeong, Yunseong; Baek, Wonjung; Kim, Hobyeong; 이태성; Cho, Beopgil; Choi, Woojae; Ha, Jae-Hyun; Park, Jaemun; Hong, Jung-Il; Kwon, Yong Seung; Seo, Jungpil; Park, Keeseong Abstract: Although alpha-MnTe has attracted renewed interest in both thermoelectric and altermagnetic contexts, direct comparisons of practically accessible synthesis routes within a common experimental framework remain limited. Here, we compare conventional solid-state reaction, arc melting and Te self-flux growth methods under a common framework of composition control and thermal history. Within the explored conditions, the phase outcome depends not only on the nominal starting composition but also on route-dependent synthesis environments, including volatilization in sealed ampoules, repeated remelting and rapid quenching in arc melting, and crystal-flux interfacial segregation in Te self-flux growth. In the solid-state route, slow heating with a slightly Mn-rich starting composition was associated with reduced MnTe2 and alpha-MnTe-dominant products. Arc melting yielded alpha-MnTe-dominant products without post-annealing, accompanied by dendritic-like microstructures. Te self-flux growth yielded single crystals, although a minor MnTe2-rich interfacial or surface layer often remained. While the present dataset does not define a rigorous phase boundary or a definitive mechanistic model, it provides a systematic comparative framework for route-dependent phase outcomes and impurity persistence in alpha-MnTe synthesis.

2026-07-31T15:00:00Z An, Sungjin Siu, Zhuo Bin Kaladzhyan, Vardan Bardarson, Jens H. Lee, Sunghun Lee, Myoung-Jae Park, Kidong Park, Jeunghee Jalil, Mansoor B. A. Seo, Jungpil Jung, Minkyung https://scholar.dgist.ac.kr/handle/20.500.11750/60420 2026-06-19T00:10:14Z 2026-05-31T15:00:00Z

Title: Quantized Conductance through Surface States in High Quality Three-Dimensional Dirac Semimetal Cd3As2 Nanowire/Nanoribbon p-n Junctions Author(s): An, Sungjin; Siu, Zhuo Bin; Kaladzhyan, Vardan; Bardarson, Jens H.; Lee, Sunghun; Lee, Myoung-Jae; Park, Kidong; Park, Jeunghee; Jalil, Mansoor B. A.; Seo, Jungpil; Jung, Minkyung Abstract: We report the observation of quantized conductance in high-mobility three-dimensional Dirac semimetal Cd3As2 nanowire and nanoribbon p-n junctions. By employing suspended device geometries with dual local gates, we form tunable p-n junctions and realize ballistic transport across sub-micron channel lengths. In a wide nanoribbon device with a channel width of similar to 330 nm, conductance plateaus appear at integer multiples of 2e(2)/h in the n-n regime under high magnetic fields. Numerical simulations suggest that these features represent unresolved spin split subbands due to the smaller subband spacing in wider channels and support the interpretation that the observed quantization may originate from surface-state-dominated conduction. In contrast, narrower nanoribbons and nanowires exhibit conductance steps of 1e(2)/h, demonstrating spin-resolved subbands likely due to enhanced confinement effects. From spin-resolved subband spectroscopy, we extract an effective Land & eacute; g-factor of similar to 43 for the first subband in the bulk gap, establishing these nanostructures as a prospective platform for fault-tolerant quantum electronics.

2026-05-31T15:00:00Z