@article{duan_li_li_semenov_kim_2015, title={Highly efficient conductance control in a topological insulator based magnetoelectric transistor}, volume={118}, ISSN={0021-8979 1089-7550}, url={http://dx.doi.org/10.1063/1.4937407}, DOI={10.1063/1.4937407}, abstractNote={The spin-momentum interlocked properties of the topological insulator (TI) surface states are exploited in a transistor-like structure for efficient conductance control in the TI-magnet system. Combined with the electrically induced magnetization rotation as part of the gate function, the proposed structure takes advantage of the magnetically modulated TI electronic band dispersion in addition to the conventional electrostatic barrier. The transport analysis coupled with the magnetic simulation predicts super-steep current-voltage characteristics near the threshold along with the GHz operating frequencies. Potential implementation to a complementary logic is also examined. The predicted characteristics are most suitable for applications requiring low power or those with small signals.}, number={22}, journal={Journal of Applied Physics}, publisher={AIP Publishing}, author={Duan, Xiaopeng and Li, Xi-Lai and Li, Xiaodong and Semenov, Yuriy G. and Kim, Ki Wook}, year={2015}, month={Dec}, pages={224502} }
 @article{li_duan_kim_2014, title={Controlling electron propagation on a topological insulator surface via proximity interactions}, volume={89}, ISSN={1098-0121 1550-235X}, url={http://dx.doi.org/10.1103/PhysRevB.89.045425}, DOI={10.1103/physrevb.89.045425}, abstractNote={The possibility of electron beam guiding is theoretically explored on the surface of a topological insulator through the proximity interaction with a magnetic material. The electronic band modification induced by the exchange coupling at the interface defines the path of electron propagation in analogy to the optical fiber for photons. Numerical simulations indicate the guiding efficiency is much higher than that in the ``waveguide'' formed by an electrostatic potential barrier such as $p$-$n$ junctions. Furthermore, the results illustrate effective flux control and beam steering that can be realized by altering the magnetization/spin texture of the adjacent magnetic materials. Specifically, the feasibility to switch on and off and make a large-angle turn is demonstrated under realistic conditions. Potential implementation to logic and interconnect applications is also examined in connection with electrically controlled magnetization switching.}, number={4}, journal={Physical Review B}, publisher={American Physical Society (APS)}, author={Li, Xiaodong and Duan, Xiaopeng and Kim, Ki Wook}, year={2014}, month={Jan} }
 @article{jin_li_mullen_kim_2014, title={Intrinsic transport properties of electrons and holes in monolayer transition-metal dichalcogenides}, volume={90}, ISSN={1098-0121 1550-235X}, url={http://dx.doi.org/10.1103/PhysRevB.90.045422}, DOI={10.1103/physrevb.90.045422}, abstractNote={Intrinsic electron- and hole-phonon interactions are investigated in monolayer transition-metal dichalcogenides $M{X}_{2}$ (M=Mo, W; X=S, Se) based on a density functional theory formalism. Due to their structural similarities, all four materials exhibit qualitatively comparable scattering characteristics with the acoustic phonons playing a dominant role near the conduction and valence band extrema at the K point. However, substantial differences are observed quantitatively leading to disparate results in the transport properties. Of those considered, ${\mathrm{WS}}_{2}$ provides the best performance for both electrons and holes with high mobilities and saturation velocities in the full-band Monte Carlo analysis of the Boltzmann transport equation. It is also found that monolayer $M{X}_{2}$ crystals with an exception of ${\mathrm{MoSe}}_{2}$ generally show hole mobilities comparable to or even larger than the value for bulk silicon at room temperature, suggesting a potential opportunity in p-type devices. The analysis is extended to estimate the effective deformation potential constants for a simplified treatment as well.}, number={4}, journal={Physical Review B}, publisher={American Physical Society (APS)}, author={Jin, Zhenghe and Li, Xiaodong and Mullen, Jeffrey T. and Kim, Ki Wook}, year={2014}, month={Jul} }
 @inproceedings{duan_li_semenov_kim_2014, title={Proposal of a topological insulator based magnetoelectric transistor}, DOI={10.1109/drc.2014.6872341}, abstractNote={A new type of transistor is proposed based on wave-guiding phenomena of topological insulator (TI) surface electrons for applications in CMOS-like circuits and switchable interactions in spin logic circuits. The carrier channel is patterned by the magnetic strip and the ON/OFF switch is achieved by the electrically controlled magnetic valve (Fig. 1A). We characterized the current-gate voltage (Id-Vg) relation and the time resolved performance. Very low subthreshold swing (below 10 mV/dec) and operating frequency above 1 GHz are expected.}, booktitle={2014 72nd annual device research conference (drc)}, author={Duan, X. P. and Li, X. D. and Semenov, Y. G. and Kim, K. W.}, year={2014}, pages={149–150} }
 @article{duan_li_semenov_kim_2014, title={Quasi-optical electron transport across a magnetically induced junction on a topological insulator surface}, volume={116}, ISSN={0021-8979 1089-7550}, url={http://dx.doi.org/10.1063/1.4903798}, DOI={10.1063/1.4903798}, abstractNote={Quasi-optical Dirac electron transport is theoretically analyzed at the magnetic boundaries on a topological insulator (TI) surface. The electronic band mismatch induced by the spatially varying magnetization profile can form an effective junction akin to the electrostatic potential step. The transmission/reflection characteristics show a direct dependence on electron energy and incident angle with highly asymmetric patterns. The investigation also illustrates a nontrivial anomalous Hall current along the boundary which is further shown by a numerical simulation based on the finite-difference time-domain method. The results provide key design guidelines for prospective quasi-optical devices based on the TI-magnet heterostructures.}, number={22}, journal={Journal of Applied Physics}, publisher={AIP Publishing}, author={Duan, Xiaopeng and Li, Xiaodong and Semenov, Yuriy G. and Kim, Ki Wook}, year={2014}, month={Dec}, pages={224301} }
 @article{li_semenov_kim_2014, title={Thin-film topological insulator-ferromagnet heterostructures for terahertz detection}, volume={104}, ISSN={0003-6951 1077-3118}, url={http://dx.doi.org/10.1063/1.4865423}, DOI={10.1063/1.4865423}, abstractNote={An atomically thin topological insulator is investigated theoretically for long-wavelength photodetection when it interacts with a magnetic material. Through the coupling between top and bottom surfaces as well as the exchange interaction with the proximate ferromagnet, the distribution of optically excited carriers exhibits unique patterns that depend sensitively on the frequency of the incoming light. This effect results in the generation of strong nonzero photocurrent, leading potentially to room-temperature detection of far-infrared/THz radiation with the advantage of low noise and fast response. The ease of frequency tuning by an external electrical bias offers an added versatility in the realistic implementation.}, number={6}, journal={Applied Physics Letters}, publisher={AIP Publishing}, author={Li, Xiaodong and Semenov, Yuriy G. and Kim, Ki Wook}, year={2014}, month={Feb}, pages={061116} }
 @article{li_mullen_jin_borysenko_buongiorno nardelli_kim_2013, title={Intrinsic electrical transport properties of monolayer silicene and MoS2from first principles}, volume={87}, ISSN={1098-0121 1550-235X}, url={http://dx.doi.org/10.1103/PhysRevB.87.115418}, DOI={10.1103/physrevb.87.115418}, abstractNote={Article on intrinsic electrical transport properties of monolayer silicene and MoS₂ from first principles.}, number={11}, journal={Physical Review B}, publisher={American Physical Society (APS)}, author={Li, Xiaodong and Mullen, Jeffrey T. and Jin, Zhenghe and Borysenko, Kostyantyn M. and Buongiorno Nardelli, M. and Kim, Ki Wook}, year={2013}, month={Mar} }
 @article{semenov_li_kim_2012, title={Tunable photogalvanic effect on topological insulator surfaces via proximity interactions}, volume={86}, ISSN={1098-0121 1550-235X}, url={http://dx.doi.org/10.1103/PhysRevB.86.201401}, DOI={10.1103/physrevb.86.201401}, abstractNote={An unusual photo-galvanic effect is predicted on the topological insulator surface when its semi-metallic electronic spectrum is modified by an adjacent ferromagnet. The effect is correlated with light absorption in a wide frequency range (from a few to hundreds of meV) and produces a pronounced response that is not only resonant to the photon energy but also tunable by an external electrical bias. The exceptionally strong peak photocurrent of the order of $\mu$A/cm may be achieved at elevated temperatures with the illumination power of 1 W/cm$^2$ in the THz range on Bi$_2$Se$_3$. These advantages could enable room-temperature detection of far-infrared radiation.}, number={20}, journal={Physical Review B}, publisher={American Physical Society (APS)}, author={Semenov, Yuriy G. and Li, Xiaodong and Kim, Ki Wook}, year={2012}, month={Nov} }
 @article{li_borysenko_nardelli_kim_2011, title={Electron transport properties of bilayer graphene}, volume={84}, ISSN={1098-0121 1550-235X}, url={http://dx.doi.org/10.1103/PhysRevB.84.195453}, DOI={10.1103/physrevb.84.195453}, abstractNote={Electron transport in bilayer graphene is studied by using a first principles analysis and theMonte Carlo simulation under conditions relevant to potential applications. While the intrinsic properties are found to be much less desirable in bilayer than in monolayer graphene, with significantly reduced mobilities and saturation velocities, the calculation also reveals the dominant influence of extrinsic factors such as the substrate and impurities. Accordingly, the difference between two graphene forms are more muted in realistic settings although the velocity-field characteristics remain substantially lower in the bilayer. When bilayer graphene is subject to an interlayer bias, the resulting changes in the energy dispersion lead to stronger electron scattering at the bottom of the conduction band. The mobility decreases significantly with the size of the generated bandgap, whereas the saturation velocity remains largely unaffected.}, number={19}, journal={Physical Review B}, publisher={American Physical Society (APS)}, author={Li, X. and Borysenko, K. M. and Nardelli, M. Buongiorno and Kim, K. W.}, year={2011}, month={Nov} }
 @article{li_barry_zavada_buongiorno nardelli_kim_2010, title={Surface polar phonon dominated electron transport in graphene}, volume={97}, ISSN={0003-6951 1077-3118}, url={http://dx.doi.org/10.1063/1.3525606}, DOI={10.1063/1.3525606}, abstractNote={The effects of surface polar phonons on the electronic transport properties of monolayer graphene are studied by using a Monte Carlo simulation. Specifically, the low-field electron mobility and saturation velocity are examined for different substrates (SiC, SiO2, and HfO2) in comparison to the intrinsic case. While the results show that the low-field mobility can be substantially reduced by the introduction of surface polar phonon scattering, corresponding degradation of the saturation velocity is not observed for all three substrates at room temperature. It is also found that surface polar phonons can influence graphene’s electrical resistivity even at low temperature, leading potentially to inaccurate estimation of the acoustic phonon deformation potential constant.}, number={23}, journal={Applied Physics Letters}, publisher={AIP Publishing}, author={Li, X. and Barry, E. A. and Zavada, J. M. and Buongiorno Nardelli, M. and Kim, K. W.}, year={2010}, month={Dec}, pages={232105} }