Quantized Hall conductance and its sign reversal in field-induced spin-density waves
Abstract
The sign-reversal phenomenon of the quantized Hall conductance as a function of an external magnetic field (H) observed in (TMTSF)2X is investigated theoretically. After giving a general Hall-conductance formula written in terms of order parameters of the field-induced spin-density wave (FISDW), we have done extensive mean-field calculations for a simplified standard model. It is shown that the many competing order parameters Δn (n=0,+/-1,+/-2, . . .) which coexist in a FISDW state can make the sign of the Hall constant change particularly near the subphase boundary of the FISDW and that numbering of the integer subphases (N=0,1,2, . . . stabilized in this order from high fields) does not necessarily coincide with the Hall number L defined by L=σxy/(e2/h). We have found that the jumps of the Hall constant are accompanied by the spin-density wave gap closing when a FISDW is continuously evolving as H varies. In order for the sign reversal to occur a FISDW must contain many order parameters Δn with n being both signs.
- Publication:
-
Physical Review B
- Pub Date:
- July 1994
- DOI:
- 10.1103/PhysRevB.50.921
- Bibcode:
- 1994PhRvB..50..921M
- Keywords:
-
- 73.40.Hm;
- 74.70.Kn;
- 75.30.Fv;
- Organic superconductors;
- Spin-density waves