G. Bihlmayer - Academia.edu (original) (raw)
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Papers by G. Bihlmayer
Physical Review B - Condensed Matter and Materials Physics, 2005
ABSTRACT The surface structure of Bi(111) was investigated by low-energy electron diffraction (LE... more ABSTRACT The surface structure of Bi(111) was investigated by low-energy electron diffraction (LEED) intensity analysis for temperatures between 140 and 313 K and by first-principles calculations. The diffraction pattern reveals a (1x1) surface structure and LEED intensity versus energy simulations confirm that the crystal is terminated with a Bi bilayer. Excellent agreement is obtained between the calculated and measured diffraction intensities in the whole temperature range. The first interlayer spacing shows no significant relaxation at any temperature while the second interlayer spacing expands slightly. The Debye temperatures deduced from the optimized atomic vibrational amplitudes for the two topmost layers are found to be significantly lower than in the bulk. The experimental results for the relaxations agree well with those of our first-principles calculation.
Applied Physics A: Materials Science & Processing, 2002
... We explore this subject by carrying out self-consistent calculations with the the full-potent... more ... We explore this subject by carrying out self-consistent calculations with the the full-potential linearized augmented plane-wave (FLAPW) method in film geometry [10,11] as implemented in the program FLEUR. We have extended our FLAPW program to deal with non-collinear ...
The surface structure of Bi͑110͒ has been investigated by low-energy electron diffraction intensi... more The surface structure of Bi͑110͒ has been investigated by low-energy electron diffraction intensity analysis and by first-principles calculations. Diffraction patterns at a sample temperature of 110 K and normal incidence reveal a bulk truncated ͑1 ϫ 1͒ surface without indication of any structural reconstruction despite the presence of dangling bonds on the surface layer. Good agreement is obtained between the calculated and measured diffraction intensities for this surface containing only one mirror-plane symmetry element and a buckled bilayer structure. No significant interlayer spacing relaxations are found. The Debye temperature for the surface layer is found to be lower than in the bulk, which is indicative of larger atomic vibrational amplitudes at the surface. Meanwhile, the second layer shows a Debye temperature close to the bulk value. The experimental results for the relaxations agree well with those of our first-principles calculation.
A topologically ordered material is characterized by a rare quantum organization of electrons tha... more A topologically ordered material is characterized by a rare quantum organization of electrons that evades the conventional spontaneously broken symmetry based classification of condensed matter. Exotic spin transport phenomena such as the dissipationless quantum spin Hall effect have been speculated to originate from a novel topological order whose identification requires a spin sensitive measurement, which does not exist to this date in any system (neither in Hg(Cd)Te quantum wells nor in the topological insulator BiSb). Using Mott polarimetry, we probe the spin degrees of freedom of these quantum spin Hall states and demonstrate that topological quantum numbers are uniquely determined from spin texture imaging measurements. Applying this method to the Bi{1-x}Sb{x} series, we identify the origin of its novel order and unusual chiral properties. These results taken together constitute the first observation of surface electrons collectively carrying a geometrical quantum (Berry's) phase and definite chirality (mirror Chern number, n_M =-1), which are the key electronic properties for realizing topological computing bits with intrinsic spin Hall-like topological phenomena. Our spin-resolved results not only provides the first clear proof of a topological insulating state in nature but also demonstrate the utility of spin-resolved ARPES technique in measuring the quantum spin Hall phases of matter.
We report high-resolution spin-resolved photoemission spectroscopy (Spin-ARPES) measurements on t... more We report high-resolution spin-resolved photoemission spectroscopy (Spin-ARPES) measurements on the parent compound Sb of the first discovered 3D topological insulator Bi1−xSbx [D. Hsieh et al., Nature 452, 970 (2008) Submitted 2007. By modulating the incident photon energy, we are able to map both the bulk and (111) surface band structure, from which we directly demonstrate that the surface bands are spin polarized by the spin-orbit interaction and connect the bulk valence and conduction bands in a topologically non-trivial way. A unique asymmetric Dirac surface state gives rise to a k-splitting of its spin polarized electronic channels. These results complement our previously published works on this materials class and re-confirm our discovery of first bulk (3D) topological insulator -topological order in bulk solids.
Physical Review B, 2005
The structural and electronic properties of La 2 Zr 2 O 7 and La 2 Hf 2 O 7 pyrochlore compounds ... more The structural and electronic properties of La 2 Zr 2 O 7 and La 2 Hf 2 O 7 pyrochlore compounds were investigated using the first principles full-potential linearized augmented plane wave method within the density functional theory. In this approach, the generalized gradient approximation was used for the exchange-correlation potential. We have optimized the internal structure parameter and then calculated the ground-state energy, the lattice constant, the bulk modulus, and its pressure derivative. The interatomic distances and angles were also determined. The results are in good agreement with available experimental measurements. Our electronic structure calculations predict a direct band gap at the ⌫ point; the nature of chemical bonding is dominated by the presence of ionic character. Furthermore, both La 2 Zr 2 O 7 and La 2 Hf 2 O 7 compounds are found to be insulating, which is in good agreement with experimental data.
Physical Review B - Condensed Matter and Materials Physics, 2005
ABSTRACT The surface structure of Bi(111) was investigated by low-energy electron diffraction (LE... more ABSTRACT The surface structure of Bi(111) was investigated by low-energy electron diffraction (LEED) intensity analysis for temperatures between 140 and 313 K and by first-principles calculations. The diffraction pattern reveals a (1x1) surface structure and LEED intensity versus energy simulations confirm that the crystal is terminated with a Bi bilayer. Excellent agreement is obtained between the calculated and measured diffraction intensities in the whole temperature range. The first interlayer spacing shows no significant relaxation at any temperature while the second interlayer spacing expands slightly. The Debye temperatures deduced from the optimized atomic vibrational amplitudes for the two topmost layers are found to be significantly lower than in the bulk. The experimental results for the relaxations agree well with those of our first-principles calculation.
Applied Physics A: Materials Science & Processing, 2002
... We explore this subject by carrying out self-consistent calculations with the the full-potent... more ... We explore this subject by carrying out self-consistent calculations with the the full-potential linearized augmented plane-wave (FLAPW) method in film geometry [10,11] as implemented in the program FLEUR. We have extended our FLAPW program to deal with non-collinear ...
The surface structure of Bi͑110͒ has been investigated by low-energy electron diffraction intensi... more The surface structure of Bi͑110͒ has been investigated by low-energy electron diffraction intensity analysis and by first-principles calculations. Diffraction patterns at a sample temperature of 110 K and normal incidence reveal a bulk truncated ͑1 ϫ 1͒ surface without indication of any structural reconstruction despite the presence of dangling bonds on the surface layer. Good agreement is obtained between the calculated and measured diffraction intensities for this surface containing only one mirror-plane symmetry element and a buckled bilayer structure. No significant interlayer spacing relaxations are found. The Debye temperature for the surface layer is found to be lower than in the bulk, which is indicative of larger atomic vibrational amplitudes at the surface. Meanwhile, the second layer shows a Debye temperature close to the bulk value. The experimental results for the relaxations agree well with those of our first-principles calculation.
A topologically ordered material is characterized by a rare quantum organization of electrons tha... more A topologically ordered material is characterized by a rare quantum organization of electrons that evades the conventional spontaneously broken symmetry based classification of condensed matter. Exotic spin transport phenomena such as the dissipationless quantum spin Hall effect have been speculated to originate from a novel topological order whose identification requires a spin sensitive measurement, which does not exist to this date in any system (neither in Hg(Cd)Te quantum wells nor in the topological insulator BiSb). Using Mott polarimetry, we probe the spin degrees of freedom of these quantum spin Hall states and demonstrate that topological quantum numbers are uniquely determined from spin texture imaging measurements. Applying this method to the Bi{1-x}Sb{x} series, we identify the origin of its novel order and unusual chiral properties. These results taken together constitute the first observation of surface electrons collectively carrying a geometrical quantum (Berry's) phase and definite chirality (mirror Chern number, n_M =-1), which are the key electronic properties for realizing topological computing bits with intrinsic spin Hall-like topological phenomena. Our spin-resolved results not only provides the first clear proof of a topological insulating state in nature but also demonstrate the utility of spin-resolved ARPES technique in measuring the quantum spin Hall phases of matter.
We report high-resolution spin-resolved photoemission spectroscopy (Spin-ARPES) measurements on t... more We report high-resolution spin-resolved photoemission spectroscopy (Spin-ARPES) measurements on the parent compound Sb of the first discovered 3D topological insulator Bi1−xSbx [D. Hsieh et al., Nature 452, 970 (2008) Submitted 2007. By modulating the incident photon energy, we are able to map both the bulk and (111) surface band structure, from which we directly demonstrate that the surface bands are spin polarized by the spin-orbit interaction and connect the bulk valence and conduction bands in a topologically non-trivial way. A unique asymmetric Dirac surface state gives rise to a k-splitting of its spin polarized electronic channels. These results complement our previously published works on this materials class and re-confirm our discovery of first bulk (3D) topological insulator -topological order in bulk solids.
Physical Review B, 2005
The structural and electronic properties of La 2 Zr 2 O 7 and La 2 Hf 2 O 7 pyrochlore compounds ... more The structural and electronic properties of La 2 Zr 2 O 7 and La 2 Hf 2 O 7 pyrochlore compounds were investigated using the first principles full-potential linearized augmented plane wave method within the density functional theory. In this approach, the generalized gradient approximation was used for the exchange-correlation potential. We have optimized the internal structure parameter and then calculated the ground-state energy, the lattice constant, the bulk modulus, and its pressure derivative. The interatomic distances and angles were also determined. The results are in good agreement with available experimental measurements. Our electronic structure calculations predict a direct band gap at the ⌫ point; the nature of chemical bonding is dominated by the presence of ionic character. Furthermore, both La 2 Zr 2 O 7 and La 2 Hf 2 O 7 compounds are found to be insulating, which is in good agreement with experimental data.