The dynamics of spin-density waves
- Department of Physics and Solid State Science Center, University of California-Los Angeles, Los Angeles, California 90024 (United States)
Spin-density waves (SDWs) are broken-symmetry ground states of metals, the name referring to the periodic modulation of the spin density with period, [lambda][sub 0]=[pi]/[ital k][sub [ital F]], determined by the Fermi wave vector [ital k][sub [ital F]]. The state, originally postulated by Overhauser, has been found in several organic linear-chain compounds. The development of the SDW state opens up a gap in the single-particle excitation spectrum, and the ground state is close to that of an antiferromagnet, as shown by a wide range of magnetic studies. Because of the magnetic ground state and of the incommensurate periodic spin modulation (which can be thought of as two periodic charge modulations in the two spin subbands), both collective charge and spin excitations may occur. These couple to ac magnetic and electric fields, which leads to antiferromagnetic resonances and frequency-dependent collective-mode conductivity. Both have been observed in the spin-density-wave ground state. The interaction of the collective mode with impurities pins the mode to the underlying lattice, and therefore the collective-mode charge excitations occur at finite frequencies in the long-wavelength limit. The mode can also be induced to execute a translational motion upon the application of a dc field which exceeds the threshold field [ital E][sub [ital T]]. Many of the observations on the ac, and on the nonlinear dc, response are similar to those which occur in materials with a charge-density-wave ground state. At low temperatures a novel type of collective transport suggestive of a tunneling process is observed. These low-temperature phenomena remain unexplained.
- OSTI ID:
- 5000231
- Journal Information:
- Reviews of Modern Physics; (United States), Vol. 66:1; ISSN 0034-6861
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
SUPERCONDUCTIVITY AND SUPERFLUIDITY
METALS
COLLECTIVE EXCITATIONS
ELECTRIC CONDUCTIVITY
ELECTRODYNAMICS
FREQUENCY DEPENDENCE
GINZBURG-LANDAU THEORY
GROUND STATES
IMPURITIES
MEAN-FIELD THEORY
SYMMETRY BREAKING
ELECTRICAL PROPERTIES
ELEMENTS
ENERGY LEVELS
ENERGY-LEVEL TRANSITIONS
EXCITATION
PHYSICAL PROPERTIES
665430* - Other Topics in Quantum Fluids & Solids- (1992-)