Volume 77, Number 2, January 2007
Article Number 27001
Number of page(s) 5
Section Condensed Matter: Electronic Structure, Electrical, Magnetic and Optical Properties
Published online 10 January 2007
EPL, 77 (2007) 27001
DOI: 10.1209/0295-5075/77/27001

Experimental determination of the Fermi surface of the spin spiral compound $\chem{TICo_2Se_2}$

H.-K. Jeong1, T. Valla2, R. Berger3, P. D. Johnson2 and K. E. Smith1

1  Department of Physics, Boston University - Boston, MA 02215, USA
2  Condensed Matter Physics and Materials Science Division, Brookhaven National Laboratory - Upton NY 11973, USA
3  Department of Materials Chemistry, Uppsala University - Box 538, S-75121, Uppsala, Sweden

received 11 September 2006; accepted in final form 15 November 2006; published January 2007
published online 10 January 2007

The electronic structure of ${\rm TlCo}_{2}{\rm Se}_{2}$ has been measured using high resolution angle resolved photoemission spectroscopy. ${\rm TlCo}_{2}{\rm Se}_{2}$ is thought to be an example of an incommensurate spin spiral system, where the magnetic moments of the cobalt layers are aligned ferromagnetically in the ab plane, but the magnetic moments are rotated by $\sim 121^{\circ }$ along the c-axis. However, experimental evidence in the electronic structure supporting spin spiral states has been lacking. Our experimental results clearly show the existence of band crossings near the Fermi level that are consistent with such states. Our data also reveal a remarkably heavily nested square Fermi surface in the plane perpendicular to the spin spiral, confirming the predicted quasi$\hbox{--} $two-dimensional electronic structure.

79.60.Bm - Clean metal, semiconductor, and insulator surfaces .
71.20.Be - Transition metals and alloys .
71.18.+y - Fermi surface: calculations and measurements; effective mass, g factor .

© Europhysics Letters Association 2007