scholarly journals Anomalous surface states at interfaces inp-wave superconductors

2014 ◽  
Vol 90 (6) ◽  
Author(s):  
S. V. Bakurskiy ◽  
A. A. Golubov ◽  
M. Yu. Kupriyanov ◽  
K. Yada ◽  
Y. Tanaka
Keyword(s):  
Surface States ◽  
Anomalous Surface

scholarly journals Symmetry Indicators and Anomalous Surface States of Topological Crystalline Insulators

2018 ◽  
Vol 8 (3) ◽  
Author(s):  
Eslam Khalaf ◽  
Hoi Chun Po ◽  
Ashvin Vishwanath ◽  
Haruki Watanabe
Keyword(s):  
Surface States ◽  
Anomalous Surface ◽  
Topological Crystalline Insulators

scholarly journals Are the surface Fermi arcs in Dirac semimetals topologically protected?

2016 ◽  
Vol 113 (31) ◽  
pp. 8648-8652 ◽  
Author(s):  
Mehdi Kargarian ◽  
Mohit Randeria ◽  
Yuan-Ming Lu
Keyword(s):  
Chemical Potential ◽  
Surface States ◽  
Quantum Oscillation ◽  
Band Model ◽  
Fermi Surfaces ◽  
Space Groups ◽  
Angle Resolved Photoemission Spectroscopy ◽  
Fermi Arcs ◽  
Anomalous Surface ◽  
Dirac Semimetals

Motivated by recent experiments probing anomalous surface states of Dirac semimetals (DSMs) Na3Bi and Cd3As2, we raise the question posed in the title. We find that, in marked contrast to Weyl semimetals, the gapless surface states of DSMs are not topologically protected in general, except on time-reversal-invariant planes of surface Brillouin zone. We first demonstrate this finding in a minimal four-band model with a pair of Dirac nodes at k=(0,0,±Q), where gapless states on the side surfaces are protected only near kz=0. We then validate our conclusions about the absence of a topological invariant protecting double Fermi arcs in DSMs, using a K-theory analysis for space groups of Na3Bi and Cd3As2. Generically, the arcs deform into a Fermi pocket, similar to the surface states of a topological insulator, and this pocket can merge into the projection of bulk Dirac Fermi surfaces as the chemical potential is varied. We make sharp predictions for the doping dependence of the surface states of a DSM that can be tested by angle-resolved photoemission spectroscopy and quantum oscillation experiments.

scholarly journals Dirac semimetal in β-CuI without surface Fermi arcs

2018 ◽  
Vol 115 (33) ◽  
pp. 8311-8315 ◽  
Author(s):  
Congcong Le ◽  
Xianxin Wu ◽  
Shengshan Qin ◽  
Yinxiang Li ◽  
Ronny Thomale ◽  
...  
Keyword(s):  
First Principles ◽  
Surface States ◽  
Energy Difference ◽  
First Principles Calculations ◽  
Small Energy ◽  
Concrete Material ◽  
Dirac Semimetal ◽  
Fermi Arcs ◽  
Anomalous Surface ◽  
Weyl Semimetals

Anomalous surface states with Fermi arcs are commonly considered to be a fingerprint of Dirac semimetals (DSMs). In contrast to Weyl semimetals, however, Fermi arcs of DSMs are not topologically protected. Using first-principles calculations, we predict that β-cuprous iodide (β-CuI) is a peculiar DSM whose surface states form closed Fermi pockets instead of Fermi arcs. In such a fermiological Dirac semimetal, the deformation mechanism from Fermi arcs to Fermi pockets stems from a large cubic term preserving all crystal symmetries and from the small energy difference between the surface and bulk Dirac points. The cubic term in β-CuI, usually negligible in prototypical DSMs, becomes relevant because of the particular crystal structure. As such, we establish a concrete material example manifesting the lack of topological protection for surface Fermi arcs in DSMs.

Zero-loss omega-filtered REM and RHEED on the new Zeiss 912

1991 ◽  
Vol 49 ◽  
pp. 616-617
Author(s):  
J.C.H. Spence ◽  
J. Mayer
Keyword(s):  
Electron Microscopy ◽  
Materials Science ◽  
Surface States ◽  
Ccd Camera ◽  
Dark Field ◽  
Ion Pump ◽  
Magnetic Imaging ◽  
Reflection Electron Microscopy ◽  
Diffraction Patterns ◽  
Large Background

The Zeiss 912 is a new fully digital, side-entry, 120 Kv TEM/STEM instrument for materials science, fitted with an omega magnetic imaging energy filter. Pumping is by turbopump and ion pump. The magnetic imaging filter allows energy-filtered images or diffraction patterns to be recorded without scanning using efficient parallel (area) detection. The energy loss intensity distribution may also be displayed on the screen, and recorded by scanning it over the PMT supplied. If a CCD camera is fitted and suitable new software developed, “parallel ELS” recording results. For large fields of view, filtered images can be recorded much more efficiently than by Scanning Reflection Electron Microscopy, and the large background of inelastic scattering removed. We have therefore evaluated the 912 for REM and RHEED applications. Causes of streaking and resonance in RHEED patterns are being studied, and a more quantitative analysis of CBRED patterns may be possible. Dark field band-gap REM imaging of surface states may also be possible.

Thermal Laser Stimulation Technique for AlGaN/GaN HEMT Technologies Improvement

2013 ◽  
Author(s):  
Dominique Carisetti ◽  
Nicolas Sarazin ◽  
Nathalie Labat ◽  
Nathalie Malbert ◽  
Arnaud Curutchet ◽  
...  
Keyword(s):  
Surface States ◽  
Leakage Currents ◽  
Laser Stimulation ◽  
Long Term Stability ◽  
Field Plate ◽  
Gan Hemt ◽  
Die Surface ◽  
Scan Speed ◽  
Stimulation Technique

Abstract To improve the long-term stability of AlGaN/GaN HEMTs, the reduction of gate and drain leakage currents and electrical anomalies at pinch-off is required. As electron transport in these devices is both coupled with traps or surface states interactions and with polarization effects, the identification and localization of the preeminent leakage path is still challenging. This paper demonstrates that thermal laser stimulation (TLS) analysis (OBIRCh, TIVA, XIVA) performed on the die surface are efficient to localize leakage paths in GaN based HEMTs. The first part details specific parameters, such as laser scan speed, scan direction, wavelength, and laser power applied for leakage gate current paths identification. It compares results obtained with Visible_NIR electroluminescence analysis with the ones obtained by the TLS techniques on GaN HEMT structures. The second part describes some failure analysis case studies of AlGaN/GaN HEMT with field plate structure which were successful, thanks to the OBIRCh technique.

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