Valleytronics (from ''valley'' and ''electronics'') is an experimental area in

semiconductor A semiconductor is a material which has an electrical conductivity value falling between that of a conductor, such as copper, and an insulator, such as glass. Its resistivity falls as its temperature rises; metals behave in the opposite way. ...

s that exploits local extrema ("valleys") in the

electronic band structure In solid-state physics, the electronic band structure (or simply band structure) of a solid describes the range of energy levels that electrons may have within it, as well as the ranges of energy that they may not have (called ''band gaps'' or ...

. Certain

s have multiple "valleys" in the electronic band structure of the first

Brillouin zone In mathematics and solid state physics, the first Brillouin zone is a uniquely defined primitive cell in reciprocal space. In the same way the Bravais lattice is divided up into Wigner–Seitz cells in the real lattice, the reciprocal lattice ...

, and are known as multivalley semiconductors. Valleytronics is the technology of control over the valley degree of freedom, a local maximum/minimum on the

valence Valence or valency may refer to: Science * Valence (chemistry), a measure of an element's combining power with other atoms * Degree (graph theory), also called the valency of a vertex in graph theory * Valency (linguistics), aspect of verbs rel ...

conduction band In solid-state physics, the valence band and conduction band are the bands closest to the Fermi level, and thus determine the electrical conductivity of the solid. In nonmetals, the valence band is the highest range of electron energies in ...

, of such multivalley semiconductors.

Details

The term was coined in analogy to

spintronics Spintronics (a portmanteau meaning spin transport electronics), also known as spin electronics, is the study of the intrinsic spin of the electron and its associated magnetic moment, in addition to its fundamental electronic charge, in solid-sta ...

. While in spintronics the internal degree of freedom of spin is harnessed to store, manipulate and read out bits of information, the proposal for valleytronics is to perform similar tasks using the multiple extrema of the band structure, so that the information of 0s and 1s would be stored as different discrete values of the

crystal momentum In solid-state physics crystal momentum or quasimomentum is a momentum-like vector associated with electrons in a crystal lattice. It is defined by the associated wave vectors \mathbf of this lattice, according to :_ \equiv \hbar (where \hbar ...

. Valleytronics may refer to other forms of quantum manipulation of valleys in semiconductors, including

quantum computation Quantum computing is a type of computation whose operations can harness the phenomena of quantum mechanics, such as superposition, interference, and entanglement. Devices that perform quantum computations are known as quantum computers. Thoug ...

with valley-based

qubits In quantum computing, a qubit () or quantum bit is a basic unit of quantum information—the quantum version of the classic binary bit physically realized with a two-state device. A qubit is a two-state (or two-level) quantum-mechanical system, ...

,"A valley–spin qubit in a carbon nanotube". E. A. Laird, F. Pei & L. P. Kouwenhoven. ''Nature Nanotechnology'' 8, 565–568 (2013). valley blockade and other forms of

quantum electronics Quantum optics is a branch of atomic, molecular, and optical physics dealing with how individual quanta of light, known as photons, interact with atoms and molecules. It includes the study of the particle-like properties of photons. Photons have b ...

. First experimental evidence of valley blockade predicted in Ref. (which completes the set of Coulomb charge blockade and Pauli spin blockade) has been observed in a single atom doped silicon transistor. Several theoretical proposals and experiments were performed in a variety of systems, such as

graphene Graphene () is an allotrope of carbon consisting of a Single-layer materials, single layer of atoms arranged in a hexagonal lattice nanostructure.

, few-layer phosphorene, some

transition metal dichalcogenide monolayers Transition-metal dichalcogenide (TMD or TMDC) monolayers are atomically thin semiconductors of the type MX2, with M a transition-metal atom ( Mo, W, etc.) and X a chalcogen atom ( S, Se, or Te). One layer of M atoms is sandwiched between tw ...

diamond Diamond is a solid form of the element carbon with its atoms arranged in a crystal structure called diamond cubic. Another solid form of carbon known as graphite is the chemically stable form of carbon at room temperature and pressure, ...

bismuth Bismuth is a chemical element with the symbol Bi and atomic number 83. It is a post-transition metal and one of the pnictogens, with chemical properties resembling its lighter group 15 siblings arsenic and antimony. Elemental bismuth occurs ...

silicon Silicon is a chemical element with the symbol Si and atomic number 14. It is a hard, brittle crystalline solid with a blue-grey metallic luster, and is a tetravalent metalloid and semiconductor. It is a member of group 14 in the periodic ...

carbon nanotubes A scanning tunneling microscopy image of a single-walled carbon nanotube Rotating single-walled zigzag carbon nanotube A carbon nanotube (CNT) is a tube made of carbon with diameters typically measured in nanometers. ''Single-wall carbon nan ...

aluminium arsenide Aluminium arsenide () is a semiconductor material with almost the same lattice constant as gallium arsenide and aluminium gallium arsenide and wider band gap than gallium arsenide. (AlAs) can form a superlattice with gallium arsenide ( GaAs) ...

and

silicene Silicene is a two-dimensional allotrope of silicon, with a hexagonal honeycomb structure similar to that of graphene. Contrary to graphene, silicene is not flat, but has a periodically buckled topology; the coupling between layers in silicene i ...

."Spin valleytronics in silicene: Quantum spin Hall–quantum anomalous Hall insulators and single-valley semimetals". Motohiko Ezawa, ''Phys. Rev. B'' 87, 155415 (2013)

References

External links

* Matthew Francis
"Experiments hint at a new type of electronics: valleytronics"
at ''

Ars Technica ''Ars Technica'' is a website covering news and opinions in technology, science, politics, and society, created by Ken Fisher and Jon Stokes in 1998. It publishes news, reviews, and guides on issues such as computer hardware and software, sc ...

'' ** Source of the above: Zeng, H., Dai, J., Yao, W., et al
2 monolayers by optical pumping"">"Valley polarization in MoS₂ monolayers by optical pumping"
''Nature Nanotechnology'', 7 490–493 (August 2012). . {{Authority control Quantum mechanics Semiconductors