Publications

Export 16 results:
Sort by: Author Title Type [ Year (Desc)]
2023
Holbrook, M, Chen Y, Kim H, Frammolino L, Liu M, Pan C-R, Chou M-Y, Zhang C, Shih C-K.  2023.  Creating a Nanoscale Lateral Junction in a Semiconductor Monolayer with a Large Built-in Potential. ACS NANO. 17:6966-6972. AbstractWebsite

n/a

2022
Chen, P, Chan Y-H, Liu R-Y, Zhang H-T, Gao Q, Fedorov A-V, Chou M-Y, Chiang T-C.  2022.  Dimensional crossover and symmetry transformation of charge density waves in VSe2. Phys. Rev. B. 105:161404. AbstractWebsite

n/a

2018
Chen, P, Pai WW, Chan Y-H, Madhavan V, Chou MY, Mo S-K, Fedorov A-V, Chiang T-C.  2018.  Unique Gap Structure and Symmetry of the Charge Density Wave in Single-Layer VSe2, Nov. Phys. Rev. Lett.. 121:196402.: American Physical Society AbstractWebsite

n/a

Xu, C-Z, Chan Y-H, Chen P, Wang X, Flötotto D, Hlevyack JA, Bian G, Mo S-K, Chou M-Y, Chiang T-C.  2018.  Gapped electronic structure of epitaxial stanene on InSb(111), Jan. Phys. Rev. B. 97:035122.: American Physical Society AbstractWebsite
n/a
Flötotto, D, Bai Y, Chan Y-H, Chen P, Wang X, Rossi P, Xu C-Z, Zhang C, Hlevyack JA, Denlinger JD, Hong H, Chou M-Y, Mittemeijer EJ, Eckstein JN, Chiang T-C.  2018.  In Situ Strain Tuning of the Dirac Surface States in Bi2Se3 Films, 2018. Nano LettersNano Letters. 18(9):5628-5632.: American Chemical Society AbstractWebsite
n/a
Chen, P, Pai WW, Chan Y-H, Sun W-L, Xu C-Z, Lin D-S, Chou MY, Fedorov A-V, Chiang T-C.  2018.  Large quantum-spin-Hall gap in single-layer 1T′ WSe2, 2018. 9(1):2003. AbstractWebsite

Two-dimensional (2D) topological insulators (TIs) are promising platforms for low-dissipation spintronic devices based on the quantum-spin-Hall (QSH) effect, but experimental realization of such systems with a large band gap suitable for room-temperature applications has proven difficult. Here, we report the successful growth on bilayer graphene of a quasi-freestanding WSe2 single layer with the 1T′ structure that does not exist in the bulk form of WSe2. Using angle-resolved photoemission spectroscopy (ARPES) and scanning tunneling microscopy/spectroscopy (STM/STS), we observe a gap of 129 meV in the 1T′ layer and an in-gap edge state located near the layer boundary. The system′s 2D TI characters are confirmed by first-principles calculations. The observed gap diminishes with doping by Rb adsorption, ultimately leading to an insulator–semimetal transition. The discovery of this large-gap 2D TI with a tunable band gap opens up opportunities for developing advanced nanoscale systems and quantum devices.

2017
Chen, P, Pai WW, Chan Y-H, Takayama A, Xu C-Z, Karn A, Hasegawa S, Chou MY, Mo S-K, Fedorov A-V, Chiang T-C.  2017.  Emergence of charge density waves and a pseudogap in single-layer TiTe2, 2017. 8(1):516. AbstractWebsite

Two-dimensional materials constitute a promising platform for developing nanoscale devices and systems. Their physical properties can be very different from those of the corresponding three-dimensional materials because of extreme quantum confinement and dimensional reduction. Here we report a study of TiTe2 from the single-layer to the bulk limit. Using angle-resolved photoemission spectroscopy and scanning tunneling microscopy and spectroscopy, we observed the emergence of a (2 × 2) charge density wave order in single-layer TiTe2 with a transition temperature of 92 ± 3 K. Also observed was a pseudogap of about 28 meV at the Fermi level at 4.2 K. Surprisingly, no charge density wave transitions were observed in two-layer and multi-layer TiTe2, despite the quasi-two-dimensional nature of the material in the bulk. The unique charge density wave phenomenon in the single layer raises intriguing questions that challenge the prevailing thinking about the mechanisms of charge density wave formation.

2016
Chen, P, Chan Y-H, Wong M-H, Fang X-Y, Chou MY, Mo S-K, Hussain Z, Fedorov A-V, Chiang T-C.  2016.  Dimensional Effects on the Charge Density Waves in Ultrathin Films of TiSe2. NANO LETTERS. 16(10):6331-6336.
Chen, P, Chan Y-H, Fang X-Y, Mo S-K, Hussain Z, Fedorov A-V, Chou MY, Chiang T-C.  2016.  Hidden Order and Dimensional Crossover of the Charge Density Waves in TiSe2. SCIENTIFIC REPORTS. 6:37910.
Feng, B, Chan Y-H, Feng Y, Liu R-Y, Chou MY, Kuroda K, Yaji K, Harasawa A, Moras P, Barinov A, Malaeb WG, Bareille C, Kondo T, Shin S, Komori F, Chiang T-C, Shi Y, Matsuda I.  2016.  Spin Texture in Type II Weyl Semimetal WTe2. PHYSICAL REVIEW B. 94(19):195134.
2015
Chen, P, Chan Y-H, Fang X-Y, Zhang Y, Chou MY, Mo S-K, Hussain Z, Fedorov A-V, Chiang T-C.  2015.  Charge density wave transition in single-layer titanium diselenide. Nature Communications. 6 Abstract
n/a
2014
Weng, SC, Xu RQ, Said AH, Leu BM, Ding Y, Hong H, Fang XY, Chou MY, Bosak A, Abbamonte P, Cooper SL, Fradkin E, Chang SL, Chiang TC.  2014.  Pressure-induced antiferrodistortive phase transition in SrTiO3: Common scaling of soft-mode with pressure and temperature. Epl. 107:5. AbstractWebsite
n/a
1998
Lee, E, Puzder A, Chou MY, Uzer T, Farrelly D.  1998.  Pair-tunneling states in semiconductor quantum dots: Ground-state behavior in a magnetic field, May. Physical Review B. 57:12281-12284., Number 19 AbstractWebsite

Using classical mechanical and quantum Monte Carlo methods we trace the ground-state behavior with an applied magnetic field of localized electron pair states in a quantum dot. By developing a method to treat nonconserved paramagnetic interactions using variational and diffusion quantum Monte Carlo techniques we find (i) a single-triplet transition at very small magnetic field strengths, (ii) enhanced localization of the two electrons with increasing magnetic field, and (iii) a mechanism for pair breakup that is different from that proposed recently by Wan et al. [Phys. Rev. Lett. 75, 2879 (1995)]. [S0163-1829(98)04016-8].

1997
Williamson, AJ, Rajagopal G, Needs RJ, Fraser LM, Foulkes WMC, Wang Y, Chou MY.  1997.  Elimination of Coulomb finite-size effects in quantum many-body simulations, Feb. Physical Review B. 55:R4851-R4854., Number 8 AbstractWebsite

A model interaction is introduced for quantum many-body simulations of Coulomb systems using periodic I boundary conditions. The interaction gives much smaller finite size effects than the standard Ewald interaction and is also much faster to compute. Variational quantum Monte Carlo simulations of diamond-structure silicon with up to 1000 electrons demonstrate the effectiveness of our method.

Hood, RQ, Chou MY, Williamson AJ, Rajagopal G, Needs RJ, Foulkes WMC.  1997.  Quantum Monte Carlo investigation of exchange and correlation in silicon, Apr. Physical Review Letters. 78:3350-3353., Number 17 AbstractWebsite

Realistic many-body wave functions for diamond-structure silicon are constructed for different values of the Coulomb coupling constant. The coupling-constant-integrated pair correlation function, the exchange-correlation hole, and the exchange-correlation energy density are calculated and compared with those obtained from the local density and average density approximations. We draw conclusions about the reasons for the success of the local density approximation and suggest a method for testing the effectiveness of exchange-correlation functionals.

Foulkes, WMC, Nekovee M, Hood RQ, Chou MY, Needs RJ, Rajagopal G, Williamson AJ.  1997.  Quantum Monte Carlo studies of exchange and correlation in solids, Apr. Abstracts of Papers of the American Chemical Society. 213:125-COMP. AbstractWebsite
n/a