J. Phys. IV France
Volume 114, April 2004
Page(s) 61 - 65

J. Phys. IV France
114 (2004) 61
DOI: 10.1051/jp4:2004114011

Field-induced spin-density-wave phases in TMTSF organic conductors: Quantization versus non-quantization

N. Dupuis1 and K. Sengupta2

1  Laboratoire de Physique des Solides, Bât. 510, Université Paris Sud, 91405 Orsay Cedex, France
2  Department of Physics, Yale University, New Haven, CT-06520-8120, USA

We study the magnetic-field-induced spin-density-wave (FISDW) phases in TMTSF organic conductors in the framework of the quantized nesting model. In agreement with recent suggestions, we find that the SDW wave-vector ${\bf Q}$ deviates from its quantized value near the transition temperature Tc for all phases with quantum numbers N>0. Deviations from quantization are more pronounced at low pressure and higher N and may lead to a suppression of the first-order transitions $N+1\to N$ for $N\ge 5$. Below a critical pressure, we find that the N=0 phase invades the entire phase diagram in accordance with earlier experiments. We also show that at T=0, the quantization of ${\bf Q}$ and hence the Hall conductance is always exact. Our results suggest a novel phase transition/crossover at intermediate temperatures between phases with quantized and non-quantized ${\bf Q}$. Key words. Organic conductors - Spin-density wave - Quantum Hall effect

© EDP Sciences 2004