Lattice-Symmetry-Driven Phase Competition in Vanadium Dioxide
- PDF / 174,280 Bytes
- 5 Pages / 432 x 648 pts Page_size
- 17 Downloads / 186 Views
Lattice-Symmetry-Driven Phase Competition in Vanadium Dioxide A. Tselev,1* I . A. Luk’yanchuk,2 I. N. Ivanov,1 J. D. Budai,1 J. Z. Tischler,1 E. Strelcov,3 A. Kolmakov,3 and S. V. Kalinin1 1 Oak Ridge National Laboratory, Oak Ridge, TN 37831 2 Laboratory of Condensed Matter Physics, University of Picardie Jules Verne, Amiens, 80039, France 3 Physics Department, Southern Illinois University Carbondale, Carbondale, IL 62901 ABSTRACT We performed group-theoretical analysis of the symmetry relationships between lattice structures of R, M1, M2, and T phases of vanadium dioxide in the frameworks of the general Ginzburg-Landau phase transition theory. The analysis leads to a conclusion that the competition between the lower-symmetry phases M1, M2, and T in the metal-insulator transition is pure symmetry driven, since all the three phases correspond to different directions of the same multicomponent structural order parameter. Therefore, the lower-symmetry phases can be stabilized in respect to each other by small perturbations such as doping or stress. INTRODUCTION Vanadium dioxide exhibits an abrupt, first-order metal-insulator transition (MIT) on cooling at a temperature of about Tc = 68 ºC in bulk with a few orders of magnitude change of electrical conductivity within a sub-100 fs intrinsic time scale [1, 2]. This feature makes the material an excellent candidate for diverse applications in optical, electronic, and opto-electronic devices. In particular, VO2 is considered the most promising candidate for realization of a Mott field-effect transistor, a novel fast electronic switch based on an electrostatically-induced MIT [3, 4]. However, the exact physical mechanism of the MIT is still not completely understood [2, 5-11], which hampers many of the potential applications of the material. There is strong evidence that the main driving force for the transition is electron-electron correlations, however the insulating phase stable in pure VO2 under ambient temperature and pressure—M1—should not be considered as a conventional Mott insulator due to a significant lattice contribution in the formation of the band gap [2, 8], which turns out to be an obstacle in achieving the MIT by means of external fields. Recently, a number of previously unknown aspects of the MIT in this oxide were found [4, 10, 12, 13]. In particular, several reports demonstrated that the MIT in VO2 nanobeams can proceed through competition between two monoclinic phases M1 and M2 [4, 12, 13]. The nature of such phase behavior has been remained unclear. In the M1 phase structure, V atoms are dimerized and arranged into zigzag chains along the c-axis of the parent tetragonal rutile structure (R) [14]. In contrast, in the M2 structure, only half of the V atoms are paired, and those are arranged in strictly linear chains along the rutile cR-axis, whereas the other half makes a twisted arrangement similar to that in M1 with all nearest V-V distances being equal [14]. While the pairing of vanadium atoms may contribute to the band gap formation in the M1 phase t
Data Loading...
