arXiv subjects

Eui-Cheol Shin

Publications and source records attributed to Eui-Cheol Shin.

3 recordsLinked to original sources

arXiv2025

Triboelectric charge transfer theory driven by interfacial thermoelectric effect

Despite extensive study and the practical significance of friction-driven static electricity, a quantitative triboelectric charge transfer theory has yet to be established. Here, we elucidate the detailed dynamics of triboelectric charge transfer driven by interfacial thermoelectric bias maintaining a steady state at the interface. We demonstrate that triboelectric charge exists in a delta-like distribution at a steady state. We suggest that the transferred triboelectric charge is dictated by half of the difference between thermoelectrically induced surface charges. Moreover, we quantitatively discuss electrostatic adhesion and static discharge between the transferred charges, which we may experience every day, including the role of surface charge inhomogeneity. Our findings may have significant implications for applications ranging from static electricity phenomena to advanced energy harvesting devices.

cond-mat.mtrl-sci↗

arXiv2023

Ultrafast switching of topological invariants by light-driven strain

Reversible control of the topological invariants from nontrivial to trivial states has fundamental implications for quantum information processors and spintronics, by realizing of an on/off switch for robust and dissipationless spin-current. Although mechanical strain has typically advantageous for such control of topological invariants, it is often accompanied by in-plane fractures and is not suited for high-speed, time-dependent operations. Here, we use ultrafast optical and THz spectroscopy to investigate topological phase transitions by light-driven strain in Bi$_2$Se$_3$, a material that requires substantial strain for $\mathrm{Z}_2$ switching. We show that Bi$_2$Se$_3$ experiences ultrafast switching from being a topological insulator with spin-momentum-locked surfaces, to hybridized states and normal insulating phases at ambient conditions. Light-induced strong out-of-plane strain can suppress the surface-bulk coupling, enabling differentiation of surface and bulk conductance at room temperature, far above the Debye temperature. We illustrate various time-dependent sequences of transient hybridization, as well as the switching operation of topological invariants by adjusting the photoexcitation intensity. The abrupt alterations in both surface and bulk transport near the transition point allow for coherent conductance modulation at hyper-sound frequencies. Our findings regarding light-triggered ultrafast switching of topological invariants pave the way for high-speed topological switching and its associated applications.

cond-mat.mtrl-sci↗

arXiv2022

Derivation of a governing rule in triboelectric charging and series from thermoelectricity

Friction-driven static electrification is familiar and fundamental in daily life, industry, and technology, but its basics have long been unknown and have continually perplexed scientists from ancient Greece to the modern high-tech era. Despite its simple manifestation, triboelectric charging is believed to be very complex because of the unresolvable interfacial interaction between two rubbing materials. Here, we for the first time reveal a simple physics of triboelectric charging and triboelectric series based on friction-originated thermoelectric charging effects at the interface, characterized by the material density ($ρ$), specific heat (c), thermal conductivity (k), and Seebeck coefficient (S) of each material. We demonstrate that energy dissipational heat at the interface induces temperature variations in the materials and thus develops electrostatic potentials that will initiate thermoelectric charging across the interface. We find that the trends and quantities of triboelectric charging for various polymers, metals, semiconductors, and even lightning clouds are simply governed by the triboelectric factor $ξ=S/\sqrt{ρck}$. The triboelectric figure-of-merit is expressed with the triboelectric power K=$ξ\sqrt{t/π}$, of which the difference can be maximized up to 1.2 V/W cm$^{-2}$ at the friction time t = 1 s. Our findings will bring significant opportunities for microscopic understanding and management of triboelectricity or static electrification.

cond-mat.mtrl-sci↗