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Wallpaper fermions and the nonsymmorphic Dirac insulator
Wieder, Benjamin J.,Bradlyn, Barry,Wang, Zhijun,Cano, Jennifer,Kim, Youngkuk,Kim, Hyeong-Seok D.,Rappe, Andrew M.,Kane, C. L.,Bernevig, B. Andrei American Association for the Advancement of Scienc 2018 Science Vol.361 No.6399
<P>Materials whose gapless surface states are protected by crystal symmetries include mirror topological crystalline insulators and nonsymmorphic hourglass insulators. There exists only a very limited set of possible surface crystal symmetries, captured by the 17 'wallpaper groups.' Here we show that a consideration of symmetry-allowed band degeneracies in the wallpaper groups can be used to understand previously described topological crystalline insulators and to predict phenomenologically distinct examples. In particular, the two wallpaper groups with multiple glide lines, pgg and p4g, allow for a topological insulating phase whose surface spectrum consists of only a single, fourfolddegenerate, true Dirac fermion, representing an exception to a symmetry-enhanced fermion-doubling theorem. We theoretically predict the presence of this phase in Sr2Pb3 in space group 127 (P4/mbm).</P>
Zhang, Ellen Ziyi,Oh, Wang-Yuhl,Villiger, Martin L,Chen, Liang,Bouma, Brett E,Vakoc, Benjamin J Optical Society of America 2013 Optics express Vol.21 No.1
<P>Polarization mode dispersion (PMD), which can be induced by circulators or even moderate lengths of optical fiber, is known to be a dominant source of instrumentation noise in fiber-based PS-OCT systems. In this paper we propose a novel PMD compensation method that measures system PMD using three fixed calibration signals, numerically corrects for these instrument effects and reconstructs an improved sample image. Using a frequency multiplexed PS-OFDI setup, we validate the proposed method by comparing birefringence noise in images of intralipid, muscle, and tendon with and without PMD compensation.</P>
SLIDERS FOR THE NEXT GENERATION MAGNETIC HARD DISK DRIVE SYSTEMS - NUMERICAL SIMULATION
Myung S. Jhon,Paul R. Peck,Soo-Choon Kang,Benjamin L. Wang,In-Eung Kim,Ki-Ook Park 한국자기학회 1995 韓國磁氣學會誌 Vol.5 No.5
Fundamental issues and general procedures of modeling the head disk interface (HDI) in order to provide design criteria for future ultra-low flying sliders are given. Intermittent contact and gaseous rarefaction effects are discussed using nonconventional kinetic theory. To illustrate the simulation results, we modeled IBM 3370 taper flat sliders and positive/negative bow tie sliders. Several alternative HDI concepts for future disk drives - viscoelastic bearings, a hybrid system, and contact recording - are also briefly discussed.