arXiv subjects

Hee Chul Park

Publications and source records attributed to Hee Chul Park.

41 records · Page 3Linked to original sources

arXiv2015

Poisson's Ratio of Layered Two-dimensional Crystals

We present first-principles calculations of elastic properties of multilayered two-dimensional crystals such as graphene, h-BN and 2H-MoS2 which shows that their Poisson's ratios along out-of-plane direction are negative, near zero and positive, respectively, spanning all possibilities for sign of the ratios. While the in-plane Poisson's ratios are all positive regardless of their disparate electronic and structural properties, the characteristic interlayer interactions as well as layer stacking structures are shown to determine the sign of their out-of-plane ratios. Thorough investigation of elastic properties as a function of the number of layers for each system is also provided, highlighting their intertwined nature between elastic and electronic properties.

cond-mat.mtrl-sci↗

arXiv2014

Manifestation of axion electrodynamics through magnetic ordering on edges of topological insulator

Based on a first-principles approach, we show that in a single crystal of a prototypical topological insulator such as Bi$_2$Se$_3$ the difference in the work function between adjacent surfaces with different crystal-face orientations generates a built-in electric field around facet edges. Owing to the topological magnetoelectric coupling for a given broken time-reversal symmetry in the crystal, the electric field, in turn, forces effective magnetic dipoles to accumulate along the edges, realizing the facet-edge magnetic ordering. We demonstrate that the predicted magnetic ordering which depends only on the work function difference between facets, is in fact a manifestation of the axion electrodynamics in real solids.

cond-mat.mes-hall↗

arXiv2011

Spin-thermo-electronic oscillator based on inverse giant magnetoresistance

A spin-thermo-electronic valve with the free layer of exchange-spring type and inverse magnetoresistance is investigated. The structure has S-shaped current-voltage characteristics and can exhibit spontaneous oscillations when integrated with a conventional capacitor within a resonator circuit. The frequency of the oscillations can be controlled from essentially dc to the GHz range by the circuit capacitance.

cond-mat.mes-hall↗

arXiv2008

Admittance and noise in an electrically driven nano-structure: Interplay between quantum coherence and statistics

We investigate the interplay between the quantum coherence and statistics in electrically driven nano-structures. We obtain expression for the admittance and the current noise for a driven nano-capacitor in terms of the Floquet scattering matrix and derive a non-equilibrium fluctuation-dissipation relation. As an interplay between the quantum phase coherence and the many-body correlation, the admittance has peak values whenever the noise power shows a step as a function of near-by gate voltage. Our theory is demonstrated by calculating the admittance and noise of driven double quantum dots.

cond-mat.mes-hall↗

arXiv2006

Spontaneously Symmetry-Broken Current in Coupled Nanomechanical Shuttles

We investigate the transport and the dynamical properties of tunnel-coupled double charge shuttles. The oscillation frequencies of two shuttles are mode-locked to integer multiples of the applied voltage frequency $ω$. We show that left/right-symmetric double shuttles may generate direct net current due to bistable motions caused by parametric instability. The symmetry-broken direct current appears near $ω=Ω_{0}/(2j-1)$, ($j=1,2,...$), where $Ω_{0}$ is the dressed resonance frequency of the relative motion of the two shuttles.

cond-mat.mes-hall↗