Names | |
---|---|
IUPAC name selenoxobismuth, selanylidenebismuth [1] | |
Identifiers | |
3D model (JSmol) | |
ChemSpider | |
ECHA InfoCard | 100.031.901 |
EC Number |
|
PubChem CID | |
UNII | |
CompTox Dashboard (EPA) | |
| |
| |
Properties | |
Bi2Se3 | |
Molar mass | 654.8 g/mol [2] |
Appearance | Dull grey [3] |
Density | 6.82 g/cm3 [2] |
Melting point | 710 °C (1,310 °F; 983 K) [2] |
insoluble | |
Solubility | insoluble in organic solvents soluble in strong acids [2] |
Structure | |
rhombohedral | |
Thermochemistry | |
Std enthalpy of formation (ΔfH⦵298) | -140 kJ/mol |
Hazards | |
Occupational safety and health (OHS/OSH): | |
Main hazards | Toxic [3] |
NFPA 704 (fire diamond) | |
Related compounds | |
Other anions | Bismuth(III) oxide Bismuth trisulfide Bismuth telluride |
Other cations | Arsenic triselenide Antimony triselenide |
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa). |
Bismuth selenide (Bi2Se3) is a gray compound of bismuth and selenium also known as bismuth(III) selenide.
Bismuth selenide is a semiconductor and a thermoelectric material. [4] While stoichiometric bismuth selenide should be a semiconductor with a gap of 0.3 eV, naturally occurring selenium vacancies act as electron donors, so Bi2Se3 is intrinsically n-type. [5] [6] [7]
Bismuth selenide has a topologically insulating ground-state. [8] Topologically protected Dirac cone surface states have been observed in Bismuth selenide and its insulating derivatives leading to intrinsic topological insulators, [6] [9] [10] [11] which later became the subject of world-wide scientific research. [12] [13] [14] [15]
Bismuth selenide is a van der Waals material consisting of covalently bound five-atom layers (quintuple layers) which are held together by van der Waals interactions [16] and spin-orbit coupling effects. [17] Although the (0001) surface is chemically inert (mostly due to the inert-pair effect of Bi [17] ), there are metallic surface states, protected by the non-trivial topology of the bulk. For this reason, the Bi2Se3 surface is an interesting candidate for van der Waals epitaxy and subject of scientific research. For instance, different phases of antimony layers can be grown on Bi2Se3, [18] [19] by means of which topological pn-junctions can be realised. [20] More intriguingly, Sb layers undergo topological phase transitions when attached to the Bi2Se3 surface and thus inherit the non-trivial topological properties of the Bi2Se3 substrate. [21] [22]
Although bismuth selenide occurs naturally (as the mineral guanajuatite) at the Santa Catarina Mine in Guanajuato, Mexico [23] as well as some sites in the United States and Europe, [24] such deposits are rare and contain a significant level of sulfur [24] atoms as an impurity. For this reason, most bismuth selenide used in research into potential commercial applications is synthesized. Commercially-produced samples are available for use in research, but the concentration of selenium vacancies is heavily dependent upon growth conditions, [25] [26] and so bismuth selenide used for research is often synthesized in the laboratory.
A stoichiometric mixture of elemental bismuth and selenium, when heated above the melting points of these elements in the absence of air, will become a liquid that freezes to crystalline Bi2Se3. [27] Large single crystals of bismuth selenide can be prepared by the Bridgman–Stockbarger method. [28]
In physics, the Kondo effect describes the scattering of conduction electrons in a metal due to magnetic impurities, resulting in a characteristic change i.e. a minimum in electrical resistivity with temperature. The cause of the effect was first explained by Jun Kondo, who applied third-order perturbation theory to the problem to account for scattering of s-orbital conduction electrons off d-orbital electrons localized at impurities. Kondo's calculation predicted that the scattering rate and the resulting part of the resistivity should increase logarithmically as the temperature approaches 0 K. Experiments in the 1960s by Myriam Sarachik at Bell Laboratories provided the first data that confirmed the Kondo effect. Extended to a lattice of magnetic impurities, the Kondo effect likely explains the formation of heavy fermions and Kondo insulators in intermetallic compounds, especially those involving rare earth elements such as cerium, praseodymium, and ytterbium, and actinide elements such as uranium. The Kondo effect has also been observed in quantum dot systems.
In physics, topological order is a kind of order in the zero-temperature phase of matter. Macroscopically, topological order is defined and described by robust ground state degeneracy and quantized non-Abelian geometric phases of degenerate ground states. Microscopically, topological orders correspond to patterns of long-range quantum entanglement. States with different topological orders cannot change into each other without a phase transition.
In particle physics, a relativistic particle is an elementary particle with kinetic energy greater than or equal to its rest-mass energy given by Einstein's relation, , or specifically, of which the velocity is comparable to the speed of light .
Bismuth telluride is a gray powder that is a compound of bismuth and tellurium also known as bismuth(III) telluride. It is a semiconductor, which, when alloyed with antimony or selenium, is an efficient thermoelectric material for refrigeration or portable power generation. Bi2Te3 is a topological insulator, and thus exhibits thickness-dependent physical properties.
A Majorana fermion, also referred to as a Majorana particle, is a fermion that is its own antiparticle. They were hypothesised by Ettore Majorana in 1937. The term is sometimes used in opposition to a Dirac fermion, which describes fermions that are not their own antiparticles.
The quantum spin Hall state is a state of matter proposed to exist in special, two-dimensional semiconductors that have a quantized spin-Hall conductance and a vanishing charge-Hall conductance. The quantum spin Hall state of matter is the cousin of the integer quantum Hall state, and that does not require the application of a large magnetic field. The quantum spin Hall state does not break charge conservation symmetry and spin- conservation symmetry.
Subir Sachdev is Herchel Smith Professor of Physics at Harvard University specializing in condensed matter. He was elected to the U.S. National Academy of Sciences in 2014, and received the Lars Onsager Prize from the American Physical Society and the Dirac Medal from the ICTP in 2018. He was a co-editor of the Annual Review of Condensed Matter Physics from 2017–2019.
A topological insulator is a material whose interior behaves as an electrical insulator while its surface behaves as an electrical conductor, meaning that electrons can only move along the surface of the material.
Antimony telluride is an inorganic compound with the chemical formula Sb2Te3. As is true of other pnictogen chalcogenide layered materials, it is a grey crystalline solid with layered structure. Layers consist of two atomic sheets of antimony and three atomic sheets of tellurium and are held together by weak van der Waals forces. Sb2Te3 is a narrow-gap semiconductor with a band gap 0.21 eV; it is also a topological insulator, and thus exhibits thickness-dependent physical properties.
Samarium hexaboride (SmB6) is an intermediate-valence compound where samarium is present both as Sm2+ and Sm3+ ions at the ratio 3:7. It is a Kondo insulator having a metallic surface state.
Weyl fermions are massless chiral fermions embodying the mathematical concept of a Weyl spinor. Weyl spinors in turn play an important role in quantum field theory and the Standard Model, where they are a building block for fermions in quantum field theory. Weyl spinors are a solution to the Dirac equation derived by Hermann Weyl, called the Weyl equation. For example, one-half of a charged Dirac fermion of a definite chirality is a Weyl fermion.
Bismuth antimonides, Bismuth-antimonys, or Bismuth-antimony alloys, (Bi1−xSbx) are binary alloys of bismuth and antimony in various ratios.
In physics, Dirac cones are features that occur in some electronic band structures that describe unusual electron transport properties of materials like graphene and topological insulators. In these materials, at energies near the Fermi level, the valence band and conduction band take the shape of the upper and lower halves of a conical surface, meeting at what are called Dirac points.
YbBiPt is an intermetallic material which at low temperatures exhibits an extremely high value of specific heat, which is a characteristic of heavy-fermion behavior. YbBiPt has a noncentrosymmetric cubic crystal structure; in particular it belongs to the ternary half-Heusler compounds.
The term Dirac matter refers to a class of condensed matter systems which can be effectively described by the Dirac equation. Even though the Dirac equation itself was formulated for fermions, the quasi-particles present within Dirac matter can be of any statistics. As a consequence, Dirac matter can be distinguished in fermionic, bosonic or anyonic Dirac matter. Prominent examples of Dirac matter are graphene and other Dirac semimetals, topological insulators, Weyl semimetals, various high-temperature superconductors with -wave pairing and liquid helium-3. The effective theory of such systems is classified by a specific choice of the Dirac mass, the Dirac velocity, the gamma matrices and the space-time curvature. The universal treatment of the class of Dirac matter in terms of an effective theory leads to a common features with respect to the density of states, the heat capacity and impurity scattering.
Magnetic topological insulators are three dimensional magnetic materials with a non-trivial topological index protected by a symmetry other than time-reversal. In contrast with a non-magnetic topological insulator, a magnetic topological insulator can have naturally gapped surface states as long as the quantizing symmetry is broken at the surface. These gapped surfaces exhibit a topologically protected half-quantized surface anomalous Hall conductivity perpendicular to the surface. The sign of the half-quantized surface anomalous Hall conductivity depends on the specific surface termination.
Photonic topological insulators are artificial electromagnetic materials that support topologically non-trivial, unidirectional states of light. Photonic topological phases are classical electromagnetic wave analogues of electronic topological phases studied in condensed matter physics. Similar to their electronic counterparts, they, can provide robust unidirectional channels for light propagation.
The Rashba–Edelstein effect (REE) is a spintronics-related effect, consisting in the conversion of a bidimensional charge current into a spin accumulation. This effect is an intrinsic charge-to-spin conversion mechanism and it was predicted in 1990 by the scientist V.M. Edelstein. It has been demonstrated in 2013 and confirmed by several experimental evidences in the following years.
Pedram Roushan is an Iranian-American physicist working at Google AI on quantum computing and quantum simulation.
Bismuth-containing solid-state compounds pose an interest to both the physical inorganic chemists as well as condensed matter physicists due to the element's massive spin-orbit coupling, stabilization of lower oxidation states, and the inert pair effect. Additionally, the stabilization of the Bi in the +1 oxidation state gives rise to a plethora of subhalide compounds with interesting electronics and 3D structures.