# Synopsis: A dilute magnetic topological semiconductor?

By doping the topological insulator ${\text{Bi}}_{2}{\text{Te}}_{3}$ with magnetic manganese, researchers have turned it into a dilute ferromagnetic semiconductor.

${\text{Bi}}_{2}{\text{Te}}_{3}$ and ${\text{Bi}}_{2}{\text{Se}}_{3}$ have a rich history as very good room-temperature thermoelectric materials, but recently they have been at the center of attention in the rapidly developing field of topological insulators. Although these materials are bulk insulators, they possess topologically protected gapless surface states, protected in the sense that they are immune to disorder, perturbations, or fluctuations. It was recently shown that doping ${\text{Bi}}_{2}{\text{Se}}_{3}$ with nonmagnetic copper results in superconductivity.

Now, in an article appearing in Physical Review B, Yew San Hor and collaborators from the chemistry and physics departments of Princeton University, US, show that doping ${\text{Bi}}_{2}{\text{Te}}_{3}$ with magnetic manganese makes the compound magnetic, while still preserving the topological surface states that are present in the parent material. Their detailed study shows that, as manganese doping levels are increased, this first gives rise to local magnetic moments, but subsequently leads to a second-order ferromagnetic transition. Scanning tunneling microscopy allows visualizing individual magnetic dopant atoms and reveals no manganese clusters, an indication that the system is a true dilute ferromagnetic semiconductor. Angle-resolved photoemission spectroscopy reveals that, although subtly altered by the doping, the topological surface states are still there just above the ferromagnetic transition temperature. – Alex Klironomos

### Announcements

More Announcements »

## Previous Synopsis

Atomic and Molecular Physics

## Next Synopsis

Atomic and Molecular Physics

## Related Articles

Semiconductor Physics

### Focus: Landmarks—Accidental Discovery Leads to Calibration Standard

The quantum Hall effect, discovered unexpectedly 35 years ago, is now the basis for defining the unit of electrical resistance. Read More »

Magnetism

### Synopsis: Spin Transport in Room-Temperature Germanium

Germanium layers can carry spin-polarized currents over several hundred nanometers at room temperature, a key asset for spintronic applications. Read More »

Semiconductor Physics

### Viewpoint: Crystal Vibrations Invert Quantum Dot Exciton

Phonons assist in creating an excitation-dominated state, or population inversion, in a single quantum dot—an effect that could be used to realize single-photon sources. Read More »