One-Dimensional Instability inBaVS3

Abstract

The 3d(1) system BaVS3 undergoes a series of remarkable electronic phase transitions. We show that the metal-insulator transition at T(MI)=70 K is associated with a structural transition announced by a huge regime of one-dimensional (1D) lattice fluctuations, detected up to 170 K. These 1D fluctuations correspond to a 2k(F)=c(*)/2 charge-density wave (CDW) instability of the d(z(2)) electron gas. We discuss the formation below T(MI) of an unconventional CDW state involving the condensation of the other V4+ 3d(1) electrons of the quasidegenerate e(t(2g)) orbitals. This study stresses the role of the orbital degrees of freedom in the physics of BaVS3 and reveals the inadequacy of current first principle band calculations to describe its electronic ground state.

Structural aspects of the metal–insulator transition in BaVS3

“…This interpretation is further confirmed by the experimental observation 18 below T MI where the excess of intensity of the Bragg reflections (proportional to ε) varies with the intensity of the superstructure satellite reflection (proportional to the square of η).…”

“…According to recent X-ray studies 12,18 , no additional structural features have been detected at the T x phase transition.…”

Dynamical mean-field theory using Wannier functions: A flexible route to electronic structure calculations of strongly correlated materials

“…At ϳ70 K a second continuous phase transition takes place, 95,96 namely a metal-insulator transition ͑MIT͒ below which BaVS 3 becomes a paramagnetic insulator. A doubling of the primitive unit cell [97][98][99] is accompanying the MIT. Together with large one-dimensional structural fluctuations along the chains 98 and additional precursive behavior for the Hall constant 91 just above T MIT , the transition scenario is reminescent of a Peierls transition into a chargedensity wave ͑CDW͒ state.…”

“…A doubling of the primitive unit cell [97][98][99] is accompanying the MIT. Together with large one-dimensional structural fluctuations along the chains 98 and additional precursive behavior for the Hall constant 91 just above T MIT , the transition scenario is reminescent of a Peierls transition into a chargedensity wave ͑CDW͒ state. Finally a third second-order transition appears to occur at ϳ30 K. This so-called "X" transition is of magnetic kind and shall announce the onset of incommensurate antiferromagnetic order 100 in the insulator.…”

Competing itinerant and localized states in strongly correlatedBaVS3

“…This observation is not only adding even more complexity to the already existing problems, but also underlines the tricky nature of the electronic structure. At ambient pressure the MIT is early announced by strong precursive behavior such as a large increase of the Hall coefficient 5 and a wide one-dimensional (1D) lattice-fluctuation regime 13 along the c axis of the system. In fact, it seems to be established 7,8,13,14 that the MIT may be described in terms of a charge-density wave (CDW) instability.…”