Skip to main content
U.S. flag

An official website of the United States government

Official websites use .gov
A .gov website belongs to an official government organization in the United States.

Secure .gov websites use HTTPS
A lock ( ) or https:// means you’ve safely connected to the .gov website. Share sensitive information only on official, secure websites.

Surface conduction of topological Dirac electrons in bulk insulating Bi2Se3



Dohun Kim, Sungjae Cho, Nicholas P. Butch, Paul Syers, Kevin Kirshenbaum, Shaffique Adam, Johnpierre Paglione, Michael S. Fuhrer


The newly-discovered three-dimensional strong topological insulators (STIs) exhibit topologically-protected Dirac surface states. While the STI surface state has been studied spectroscopically by e.g. photoemission and scanned probes, transport experiments have failed to demonstrate the most fundamental signature of the STI: ambipolar metallic electronic transport in the topological surface of an insulating bulk. Here we show that the surfaces of thin (<10 nm), low-doped Bi2Se3 (≈1017/cm3) crystals are strongly electrostatically coupled, and a gate electrode can completely remove bulk charge carriers and bring both surfaces through the Dirac point simultaneously. We observe clear surface band conduction with linear Hall resistivity and well-defined ambipolar field effect, as well as a charge-inhomogeneous minimum conductivity region. A theory of charge disorder in a Dirac band explains well both the magnitude and the variation with disorder strength of the minimum conductivity (2 to 5 e2/h per surface) and the residual (puddle) carrier density (0.4 x 1012 cm-2 to 4 x 1012 cm-2). From the measured carrier mobilities 320 cm2/Vs to 1500 cm2/Vs, the charged impurity densities 0.5 cm-2 to 2.3 x 1013 cm-2 are inferred. They are of a similar magnitude to the measured doping levels at zero gate voltage (1 x 1013 cm-2 to 3 x 1013 cm-2), identifying dopants as the charged impurities.
Nature Physics


topological insulator, Hall effect, dopants, Dirac band structure, surface states


Kim, D. , Cho, S. , Butch, N. , Syers, P. , Kirshenbaum, K. , Adam, S. , Paglione, J. and Fuhrer, M. (2012), Surface conduction of topological Dirac electrons in bulk insulating Bi2Se3, Nature Physics, [online], (Accessed June 17, 2024)


If you have any questions about this publication or are having problems accessing it, please contact

Created April 14, 2012, Updated October 12, 2021