Research brings new control over topological insulator

Mar 20, 2014

An international team of scientists investigating the electronic properties of ultra-thin films of new materials – topological insulators (TIs) - has demonstrated a new method to tune their unique properties using strain.

Topological insulators are with surfaces that host a new quantum state of matter and are insensitive to contaminants, defects and impurities. Surface electrons in TIs behave like massless Dirac particles in a similar way to electrons in graphene. Moreover, surface currents in also preserve their spin orientation and coherence on a macro scale.

The research, carried out by physicists from the University of York, UK, the University of Wisconsin, Milwaukee, USA, and the University of Cadiz, Spain is reported in the journal Nature Physics.

The ability to control the surface electronic states of TIs is a crucial step in the realisation of their potential in highly energy efficient spintronic devices.

Dr Vlado Lazarov, from York's Department of Physics, said: "These inherent properties of TIs, and the interplay between magnetism and proximity to superconductors, make topological insulators a prime platform for the realisation of solid state quantum computing devices.

"The ability to control the surface of the TIs is a crucial step in realising their potential in energy efficient devices. Through our research, we have shown that it is possible to tune the properties using strain."

Using Scanning Tunneling Microscopy at UW-Milwaukee and aberration corrected Transmission Electron Microscopy at the York-JEOL Nanocentre, the researchers demonstrated that can lift the topological order, while compressive strain can shift in energy the characteristic Dirac point.

Professor Lian Li, from UW-Milwaukee, said: "Using these advanced microscopes, we examined the low-angle tilt grain boundaries in Bi2Se3(0001) films and found that they consist of arrays of alternating edge dislocation pairs. Along the boundary, these dislocations introduce different types of strain – compressive and tensile.

"Through further tunnelling spectroscopy measurements and quantum mechanical calculations, we discovered that Dirac states are enhanced under tensile strain and destroyed under compressive strain. These findings suggest new ways to control TIs' , for example, by applying stress."

Explore further: New compound shows unusual conducting properties

More information: The paper 'Tuning Dirac states by strain in the topological insulator Bi2Se3' by Y. Liu, Y. Y. Li, S. Rajput, D. Gilks, L. Lari, P. L. Galindo, M. Weinert, V. K. Lazarov and L. Li will appear in the April edition of Nature Physics (DOI: 10.1038/NPHYS2898).

add to favorites email to friend print save as pdf

Related Stories

Researchers forward quest for quantum computing

May 23, 2013

Research teams from UW-Milwaukee and the University of York investigating the properties of ultra-thin films of new materials are helping bring quantum computing one step closer to reality.

Blocking infinity in a topological insulator

Feb 08, 2013

(Phys.org)—In bulk, topological insulators (TIs) are good insulators, but on their surface they act as metals, with a twist: the spin and direction of electrons moving across the surface of a TI are locked ...

Novel topological crystalline insulator shows mass appeal

Aug 29, 2013

Disrupting the symmetrical structure of a solid-state topological crystalline insulator creates mass in previously mass-less electrons and imparts an unexpected level of control in this nascent class of materials, an international ...

Recommended for you

A transistor-like amplifier for single photons

1 hour ago

Data transmission over long distances usually utilizes optical techniques via glass fibres – this ensures high speed transmission combined with low power dissipation of the signal. For quite some years ...

Timely arrival of Pharao space clock

Jul 28, 2014

ESA has welcomed the arrival of Pharao, an important part of ESA's atomic clock experiment that will be attached to the International Space Station in 2016.

User comments : 0