Most quantum states of matter are categorized by the symmetries they break. Note that in the topological insulator, the surface states are linear in momentum and meet at an odd number of points in k-space. In the trivial case, even a small perturbation (say, changing the chemistry of the surface) can open a gap in the surface states, but in the nontrivial case, the conducting surface states are protected. In both cases, there are allowed electron states (black lines) introduced by the surface that lie in the bulk band gap (the bulk valence and conduction bands are indicated by the green and blue lines, respectively). The sketches (bottom) show the electronic structure (energy versus momentum) for a “trivial” insulator (left) and a strong topological insulator (right), such as Bi 1 − x Sb x. In this sense, it cannot be simply transformed into the surface of a normal insulator. The metallic surface of a topological insulator is different from an ordinary surface because its metallic nature is protected by certain symmetry invariants. Illustration: Alan Stonebraker Figure 1: When we think of topology, we normally think of objects that cannot be simply transformed into each other, such as a rubber band and a Möbius strip (top). The four quantum numbers conventionally used to describe the quantum state of an electron in an atom are the principal quantum number n, the azimuthal (orbital) quantum number ℓ parallel to the field, a phenomenon known as Larmor precession.Illustration: Alan Stonebraker Figure 1: When we think of topology, we normally think of objects that cannot be simply transformed into each other, such as a rubber band and a Möbius strip (top). The term magnetic in the name refers to the magnetic dipole moment associated with each type of angular momentum, so states having different magnetic quantum numbers shift in energy in a magnetic field according to the Zeeman effect. For an electron, s is 1⁄ 2, and m s is either + 1⁄ 2 or − 1⁄ 2, often called "spin-up" and "spin-down", or α and β. The spin magnetic quantum number m s specifies the z-axis component of the spin angular momentum for a particle having spin quantum number s. It specifies the component of the orbital angular momentum that lies along a given axis, conventionally called the z-axis, so it describes the orientation of the orbital in space. The orbital magnetic quantum number ( m l or m ) distinguishes the orbitals available within a given subshell of an atom. In atomic physics, a magnetic quantum number is a quantum number used to distinguish quantum states of an electron or other particle according to its angular momentum along a given axis in space. JSTOR ( May 2016) ( Learn how and when to remove this template message). Unsourced material may be challenged and removed.įind sources: "Magnetic quantum number" – news Please help improve this article by adding citations to reliable sources. This article needs additional citations for verification.
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |