Absorption edge, urbach tail, and electron-phonon interactions in topological insulator Bi2Se3 and band insulator (Bi0.89In0.11)2Se3

2019 ◽  
Vol 114 (16) ◽  
pp. 162105 ◽  
Author(s):  
Jiajun Zhu ◽  
Yunyouyou Xia ◽  
Gang Li ◽  
Shengqiang Zhou ◽  
S. Wimmer ◽  
...  
Keyword(s):  
Topological Insulator ◽  
Absorption Edge ◽  
Urbach Tail ◽  
Band Insulator

Temperature shift of the absorption edge and Urbach tail ofZrSxSe2−xsingle crystals

2017 ◽  
Vol 95 (24) ◽  
Author(s):  
Mohamed Moustafa ◽  
Anke Wasnick ◽  
Christoph Janowitz ◽  
Recardo Manzke
Keyword(s):  
Absorption Edge ◽  
Temperature Shift ◽  
Urbach Tail

scholarly journals Experimental Observation of Temperature-Driven Topological Phase Transition in HgTe/CdHgTe Quantum Wells

2019 ◽  
Author(s):  
Maksim Zholudev ◽  
Aleksandr Kadykov ◽  
Mikhail Fadeev ◽  
Michal Marcinkiewicz ◽  
Sandra Ruffenach ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Phase Transition ◽  
Quantum Wells ◽  
Topological Insulator ◽  
Critical Magnetic Field ◽  
Topological Phase ◽  
Temperature Dependent ◽  
Transition Parameter ◽  
Topological Phase Transition ◽  
Band Insulator

We report on comparison between temperature-dependent magneto¬absorption and magnetotransport spectroscopy of HgTe/CdHgTe quantum wells in terms of detection of phase transition between topological insulator and band insulator states. Our results demonstrate that temperature-dependent magnetospectroscopy is a powerful tool to discriminate trivial and topological insulator phases, yet magnetotransport method is shown to have advantages for clear manifestation of the phase transition with accurate quantitative values of transition parameter (i.e. critical magnetic field Bc).

scholarly journals Experimental Observation of Temperature-Driven Topological Phase Transition in HgTe/CdHgTe Quantum Wells

2019 ◽  
Vol 4 (1) ◽  
pp. 27 ◽  
Author(s):  
Maksim S. Zholudev ◽  
Aleksandr M. Kadykov ◽  
Mikhail A. Fadeev ◽  
Michal Marcinkiewicz ◽  
Sandra Ruffenach ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Phase Transition ◽  
Quantum Wells ◽  
Topological Insulator ◽  
Critical Magnetic Field ◽  
Topological Phase ◽  
Temperature Dependent ◽  
Transition Parameter ◽  
Topological Phase Transition ◽  
Band Insulator

We report on the comparison between temperature-dependent magneto-absorption and magnetotransport spectroscopy of HgTe/CdHgTe quantum wells in terms of the detection of the phase transition between the topological insulator and band insulator states. Our results demonstrate that temperature-dependent magnetospectroscopy is a powerful tool to discriminate trivial and topological insulator phases, yet the magnetotransport method is shown to have advantages for the clear manifestation of the phase transition with accurate quantitative values of the transition parameter (i.e., critical magnetic field Bc).

scholarly journals Transformation of the Topological Phase and the Edge Modes of Double-Bilayer Bismuthene with Inter-Bilayer Spacing

Crystals ◽  
2019 ◽  
Vol 9 (5) ◽  
pp. 266 ◽  
Author(s):  
Huanzhi Hu ◽  
Zhibin Shi ◽  
Peng Wang ◽  
Weiping Zhou ◽  
Tai-Chang Chiang ◽  
...  
Keyword(s):  
Phase Transition ◽  
Valence Band ◽  
Conduction Band ◽  
Topological Insulator ◽  
First Principles ◽  
Topological Phase ◽  
First Principles Calculations ◽  
Topological Phase Transition ◽  
Band Inversion ◽  
Band Insulator

The transformations of the topological phase and the edge modes of a double-bilayer bismuthene were investigated with first-principles calculations and Green’s function as the inter-bilayer spacing increased from 0 Å to 10 Å. At a critical spacing of 2 Å, a topological phase transition from a topological insulator to a band insulator resulting from a band inversion between the highest valence band and the second lowest conduction band, was observed, and this was understood based on the particular orbital characters of the band inversion involved states. The edge modes of double-bilayer bismuthene survived the phase transition. When d was 2 Å < d < 4 Å, the interaction between the edge modes of two separated bismuthene bilayers induced an anti-crossing gap and resulted in a trivial band connection. At and beyond 4 Å, the two bilayers behavior decoupled entirely. The results demonstrate the transformability of the topological phase and the edge modes with the inter-bilayer spacing in double-bilayer bismuthene, which may be useful for spintronic applications.

The Electronic Absorption Edge of Petroleum

1992 ◽  
Vol 46 (9) ◽  
pp. 1405-1411 ◽  
Author(s):  
Oliver C. Mullins ◽  
Sudipa Mitra-Kirtley ◽  
Yifu Zhu
Keyword(s):  
Electronic Absorption ◽  
Absorption Edge ◽  
Spectral Region ◽  
Population Distribution ◽  
Fluorescence Emission ◽  
Crude Oils ◽  
Excitation Wavelength ◽  
Urbach Tail ◽  
Wide Range ◽  
Peak Widths

The electronic absorption spectra of more than 20 crude oils and asphaltenes are examined. The spectral location of the electronic absorption edge varies over a wide range, from the near-infrared for heavy oils and asphaltenes to the near-UV for gas condensates. The functional form of the electronic absorption edge for all crude oils (measured) is characteristic of the “Urbach tail,” a phenomenology which describes electronic absorption edges in wide-ranging materials. The crude oils all show similar Urbach widths, which are significantly larger than those generally found for various materials but are similar to those previously reported for asphaltenes. Monotonically increasing absorption at higher photon energy continues for all crude oils until the spectral region is reached where single-ring aromatics dominate absorption. However, the rate of increasing absorption at higher energies moderates, thereby deviating from the Urbach behavior. Fluorescence emission spectra exhibit small red shifts from the excitation wavelength and small fluorescence peak widths in the Urbach regions of different crude oils, but show large red shifts and large peak widths in spectral regions which deviate from the Urbach behavior. This observation implies that the Urbach spectral region is dominated by lowest-energy electronic absorption of corresponding chromophores. Thus, the Urbach tail gives a direct measure of the population distribution of chromophores in crude oils. Implied population distributions are consistent with thermally activated growth of large chromophores from small ones.

X-Ray absorption edge elemental imaging of B. thuringienis

1989 ◽  
Vol 47 ◽  
pp. 212-213
Author(s):  
R. L. Stears
Keyword(s):  
Absorption Edge ◽  
Elemental Distribution ◽  
X Rays ◽  
Differential Absorption ◽  
Synchrotron Source ◽  
High Brightness ◽  
X Ray ◽  
Elemental Imaging ◽  
Cellular Integrity ◽  
X Ray Absorption

Because of the nature of the bacterial endospore, little work has been done on analyzing their elemental distribution and composition in the intact, living, hydrated state. The majority of the qualitative analysis entailed intensive disruption and processing of the endospores, which effects their cellular integrity and composition.Absorption edge imaging permits elemental analysis of hydrated, unstained specimens at high resolution. By taking advantage of differential absorption of x-ray photons in regions of varying elemental composition, and using a high brightness, tuneable synchrotron source to obtain monochromatic x-rays, contact x-ray micrographs can be made of unfixed, intact endospores that reveal sites of elemental localization. This study presents new data demonstrating the application of x-ray absorption edge imaging to produce elemental information about nitrogen (N) and calcium (Ca) localization using Bacillus thuringiensis as the test specimen.

Reflectivity spectra of Eu rich EuO near the absorption edge

1979 ◽  
Vol 40 (3) ◽  
pp. 315-319 ◽  
Author(s):  
M. Escorne ◽  
A. Mauger ◽  
C. Godart ◽  
J.C. Achard
Keyword(s):  
Absorption Edge ◽  
Reflectivity Spectra
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