arXiv subjects

Young Jae Song

Publications and source records attributed to Young Jae Song.

3 recordsLinked to original sources

arXiv2026

Observation of Macroscopic Nonlocal Voltage at Room Temperature

Electrons in conductors suffer frequent scatterings with defects and phonons, and the diffusive macroscopic behaviors are determined by an external electric field through Ohms law. If electrons are no longer diffusive, the Ohmic description collapses. In devices composed of thin chalcogenides and YBa2Cu3O7, we observe a transition from an Ohmic conductor to a nonlocal conductor below a certain temperature. The nonlocal conductor is characterized by significant nonlocal voltages (~0.1 V) across macroscopic regions (~1 mm) that are conventionally considered to be equipotential. Nonlinear responses are an additional characteristic. Negative local resistances in a vicinal geometry support macroscopic hydrodynamic flow as the underlying mechanism, implying electron momentum conservation over incredibly long distances. This new conduction state, observable at room temperature, opens the field of nonlocal electronics and low-dissipation applications.

cond-mat.str-el↗

arXiv2020

Evidence of itinerant holes for long-range magnetic order in tungsten diselenide semiconductor with vanadium dopants

One primary concern in diluted magnetic semiconductors (DMSs) is how to establish a long-range magnetic order with a low magnetic doping concentration to maintain the gate tunability of the host semiconductor, as well as to increase Curie temperature. Two-dimensional van der Waals semiconductors have been recently investigated to demonstrate the magnetic order in DMSs; however, a comprehensive understanding of the mechanism responsible for the gate-tunable long-range magnetic order in DMSs has not been achieved yet. Here, we introduce a monolayer tungsten diselenide (WSe2) semiconductor with V dopants to demonstrate the long-range magnetic order through itinerant spin-polarized holes. The V atoms are sparsely located in the host lattice by substituting W atoms, which is confirmed by scanning tunneling microscopy and high-resolution transmission electron microscopy. The V impurity states and the valence band edge states are overlapped, which is congruent with density functional theory calculations. The field-effect transistor characteristics reveal the itinerant holes within the hybridized band; this clearly resembles the Zener model. Our study gives an insight into the mechanism of the long-range magnetic order in V-doped WSe2, which can also be used for other magnetically doped semiconducting transition metal dichalcogenides.

cond-mat.mtrl-sci↗

arXiv2011

Landau Levels and Band Bending in Few-Layer Epitaxial Graphene

The carrier density distributions in few-layer-graphene systems grown on the carbon face of silicon carbide can be altered by the presence of a scanning tunneling microscope (STM) tip used to probe top-layer electronic properties, and by a perpendicular magnetic field which induces well-defined Landau levels. Hartree approximation calculations in the perpendicular field case show that charge tends to rearrange between the layers so that the filling factors of most layers are pinned at integer values. We use our analysis to provide insight into the role of buried layers in recent few-layer-graphene STM studies and discuss the limitations of our model.

cond-mat.mes-hall↗