91福利

The Charge Density Wave (CDW) in ZrTe3 is driven by a Fermi-surface nesting of the quasi 1-dimensional Fermi surface sheet of the Te p_x orbitals. The material is made of prismatic ZrTe_3 chains that are laterally linked through Te p-bonding. The CDW develops below T_CDW = 63 K with a modulation vector q_CDW in the a*-c*-plane perpendicular to the prismatic chains.

In the bulk we have found a giant Kohn anomaly and the thermodynamic signature of the soft mode driven Peierls transition by inelastic and diffuse x-ray scattering. The temperature dependent phonon softening show strong deviations from mean field behaviour and is compatible with an order parameter of dimension n = 2 [1].

Cleavage of the crystal exposes well-ordered surfaces in the a-b plane. The opening of a gap in the electronic structure was previously observed by angle resolved photoemission (ARPES) and the full temperature dependence was discussed to be compatible with a BCS model [2]. Our new high-resolution ARPES data show all bands split in two. A comparison with first principles scalar-relativistic band structure calculations shows that the observed electronic structure is not fully compatible with the expectation from bulk ZrTe_3 [3]. Rather, a surface relaxation gives rise to a subtly modified behaviour in the top layer. The splitting arises in the bi-layer of the topmost (ZrTe3)_3 chains. This leads to the interesting conclusion that controlled modifications of the CDW system are possible at the surface and their properties can be studied by surface sensitive techniques.

References
----------

[1] M. Hoesch et al. Phys. Rev. Lett. 102 (2009) 086402.
[2] T. Yokoya et al., Phys. Rev. B 71 (2005) 140504(R).
[3] M. Hoesch et al., Phys. Rev. B 80 (2009) 075423.