arXiv subjects

H. W. Yeom

Publications and source records attributed to H. W. Yeom.

3 recordsLinked to original sources

arXiv2025

Disentangle Intertwined Interactions in Correlated Charge Density Wave with Magnetic Impurities

Magnetic impurities in strongly correlated electronic systems serve as sensitive probes to a wide range of many-body quantum phenomena. Broken symmetries in such a system can lead to inequivalent lattice sites, and magnetic impurities may interact selectively with particular orbitals or sublattices. However, the microscopic mechanisms behind such site-specific interactions have been poorly understood. Here, we explore the behavior of individual Fe adatoms on a cluster-Mott charge-density-wave (CDW) system of 1T-TaS2 utilizing scanning tunneling microscopy/spectroscopy (STM/STS) and density functional theory (DFT). Our measurements uncover pronounced site-dependent electronic states of CDW clusters with Fe adatoms, indicating distinct local coupling to cluster-Mott states. DFT calculations identify three distinct types of interactions; hybridization with localized correlated electrons, distorting the CDW cluster, and charge transfer. In particular, the hybridization of Fe 3d and half-filled Ta 5dz2 orbitals suppresses the Mott insulating state for an adatom at the center of a CDW cluster. While the results underscore a crucial role of the direct orbital hybridization and the limitation of the prevailing single-site Kondo impurity model, they suggest the possibility of controlling entangled interactions separately in a cluster Mott insulator.

cond-mat.str-el↗

arXiv2020

Superconductivity emerging from a stripe charge order in IrTe2 nanoflakes

Superconductivity in the vicinity of a competing electronic order often manifests itself with a superconducting dome, centred at a presumed quantum critical point in the phase diagram. This common feature, found in many unconventional superconductors, has supported a prevalent scenario that fluctuations or partial melting of a parent order are essential for inducing or enhancing superconductivity. Here we present a contrary example, found in IrTe2 nanoflakes of which the superconducting dome is identified well inside the parent stripe charge ordering phase in the thickness-dependent phase diagram. The coexisting stripe charge order in IrTe2 nanoflakes significantly increases the out-of-plane coherence length and the coupling strength of superconductivity, in contrast to the doped bulk IrTe2. These findings clarify that the inherent instabilities of the parent stripe phaseare sufficient to induce superconductivity in IrTe2 without its complete or partial melting. Our study highlights the thickness control as an effective means to unveil intrinsic phase diagrams of correlated vdW materials.

cond-mat.supr-con↗

arXiv2002

Stress relief as the driving force for self-assembled Bi nanolines

Stress resulting from mismatch between a substrate and an adsorbed material has often been thought to be the driving force for the self-assembly of nanoscale structures. Bi nanolines self-assemble on Si(001), and are remarkable for their straightness and length -- they are often more than 400 nm long, and a kink in a nanoline has never been observed. Through electronic structure calculations, we have found an energetically favourable structure for these nanolines that agrees with our scanning tunneling microscopy and photoemission experiments; the structure has an extremely unusual subsurface structure, comprising a double core of 7-membered rings of silicon. Our proposed structure explains all the observed features of the nanolines, and shows that surface stress resulting from the mismatch between the Bi and the Si substrate are responsible for their self-assembly. This has wider implications for the controlled growth of nanostructures on semiconductor surfaces.

cond-mat.mtrl-sci↗