Jae Kwang Lee

We report a first-principles study of ${({\text{LaAlO}}_{3})}_{m}/{({\text{SrTiO}}_{3})}_{n}$ heterostructures using density-functional theory at the $\text{LDA}+U$ level. Our results support the original explanation of Ohtomo and Hwang [Nature (London) 427, 423 (2004)] that the charge at the $n$-type interface may be due to electrostatic doping. The internal electric field in the ${\text{LaAlO}}_{3}$ layer is calculated to be $0.24\text{ }\text{V}/\text{\AA{}}$. Though it is not sufficient to c

Chemical treatment using bis(trifluoromethane) sulfonimide (TFSI) was shown to be particularly effective for increasing the photoluminescence (PL) of monolayer (1L) MoS₂, suggesting a convenient method for overcoming the intrinsically low quantum yield of this material. However, the underlying atomic mechanism of the PL enhancement has remained elusive. Here, we report the microscopic origin of the defect healing observed in TFSI-treated 1L-MoS₂ through a correlative combin

Compared with their bulk counterparts, 2D materials can sustain much higher elastic strain at which optical quantities such as bandgaps and absorption spectra governing optoelectronic device performance can be modified with relative ease. Using first-principles density functional theory and quasiparticle GW calculations, we demonstrate how uniaxial tensile strain can be utilized to optimize the electronic and optical properties of transition metal dichalcogenide lateral (in-plane) heterostructur

Graphene is an ultrathin, impervious membrane. The controlled introduction of nanoscale pores in graphene would lead to applications that involve water purification, chemical separation, and DNA sequencing. However, graphene nanopores are unstable against filling by carbon adatoms. Here, using aberration-corrected scanning transmission electron microscopy and density-functional calculations, we report that Si atoms stabilize graphene nanopores by bridging the dangling bonds around the perimeter

Using first-principles density-functional theory, we investigate the interfacial magnetoelectric coupling in a tricomponent superlattice composed of a ferromagnetic metal (FM), ferroelectric (FE), and normal metal. Using Fe/FE/Pt as a model system, we show that a net and cumulative interfacial magnetization is induced in the FM metal near the FM/FE interface. A careful analysis of the magnetic moments in Fe reveals that the interfacial magnetization is a consequence of a complex interplay of int

Li-ion mobility in ${\mathrm{LiFePO}}_{4}$, a key property for energy applications, is impeded by Fe antisite defects (${\mathrm{Fe}}_{\mathrm{Li}}$) that form in select $b$-axis channels. Here we combine first-principles calculations, statistical mechanics, and scanning transmission electron microscopy to identify the origin of the effect: Li vacancies (${V}_{\mathrm{Li}}$) are confined in one-dimensional $b$-axis channels, shuttling between neighboring ${\mathrm{Fe}}_{\mathrm{Li}}$. Segregatio

Scope Oxidative stress has been implicated in mental disorders, including depression. Chlorogenic acid (CGA), one of the abundant phenolic compounds in herbs and fruits, has the properties of a natural antioxidant and free‐radical scavenger. Therfore, we investigated the antidepressant‐like effects and active mechanisms of CGA from the extract of Crataegus pinnatifida (CP) fruit. Methods and results Depression‐like phenotypes were induced in mice by daily injection of stress hormone for 1–2 week

Piezoelectricity crystallographically exists only in the in-plane direction in two-dimensional transition metal dichalcogenides. Here, we demonstrated flexoelectricity-tunable out-of-plane piezoelectricity in semiconducting 2H-MoTe₂ flakes by creating surface corrugation. In particular, the strong out-of-plane piezoelectricity and its spatial variation depending on local flexoelectricity was observed even though crystallographically there exists only in-plane piezoelectricity. Surface

Enhancing the electronic and ionic conductivity in Li compounds can significantly impact the design of batteries. Here, we explore the influence of biaxial strain on the electronic and Li+ ion conductivities of LiFePO4 by performing first-principles calculations. We find that 4% biaxial tensile strain (BTS) leads to 15 times increase in electronic conductivity and 50 times increase in Li+ ion conductivity at 300 K, respectively. Electronic conductivity is enhanced because BTS softens lattice dis

Chronic stress can lead to depression due to elevated levels of stress hormones such as glucocorticoid. This is accompanied by an increase in reactive oxygen species (ROS) levels in the brain, which can cause dendritic spine loss and atrophy in neurons, followed by memory loss. Dicaffeoylquinic acids (diCQAs) are naturally occurring polyphenolic antioxidant compounds in Arctium lappa extracts (AL). The effects of natural derivatives of cafferoylqunic acid on stress hormone-induced depressive beh

We carry out a first-principles study of stoichiometric heterostructures composed of polar oxide ${\text{LaAlO}}_{3}$ and ferromagnetic semiconductor EuO. We show that electrostatic doping achieved by an electric field in the polar oxide leads to a fully spin-polarized two dimensional electron gas at the interface. This mechanism contrasts with a previous calculation of the ${\text{LaAlO}}_{3}/\text{EuO}$ interface in which electron doping is introduced through a nonstoichiometric ${\text{LaAlO}

distribution. The present study demonstrates that AFD and FE modes in oxide heterostructures emerge as a consequence of interplay between misfit strain and polar field, and further that their combination can be tuned to competitive or cooperative coupling by changing the interface orientation.

BACKGROUND: Imiquimod (IQ) is known as an agonist of Toll-like receptor 7 (TLR7) and is widely used to treat various infectious skin diseases. However, it causes severe itching sensation as its side effect. The precise mechanism of how IQ causes itching sensation is unknown. A recent report suggested a molecular target of IQ as TLR7 expressed in dorsal root ganglion (DRG) neurons. However, we recently proposed a TLR7-independent mechanism, in which the activation of TLR7 is not required for the