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Landau theory
About: Landau theory is a research topic. Over the lifetime, 2882 publications have been published within this topic receiving 57078 citations.
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TL;DR: In this paper, the phase transition from the tetragonal to the orthorhombic structure in La2−xSr��Sr585Sr676Sr672Sr695Sr696Sr705Sr671Sr684Sr619Sr737Sr686Sr718Sr1.
Abstract: The phase transition from the tetragonal to the orthorhombic structure in La2−x
Sr
x
CuO4+δ has been studied combining elastic and inelastic neutron scattering and specific heat measurements on the same well characterized crystals. This analysis focusses on the comparison between undoped and doped compounds. The proportionality between the orderparameter and the orthorhombic strain, predicted by the Landau theory, can be confirmed in La2−x
Sr
x
CuO4+δ in a wide concentration and temperature range. We observe different values for the critical exponent β for doped superconducting and undoped insulating crystals. The temperature dependent study of the soft modes on a metallic superconducting crystal reveals an extremely large temperature range where this mode is strongly anharmonic. The comparison with previously published data shows that the frequencies of the soft modes at low temperatures decrease with doping, i.e. with increasing charge carrier concentration.
19 citations
TL;DR: In this article, a quantum triangular antiferromagnet with an incommensurate (IC) structure due to a Dzyaloshinskii-Moriya interaction is investigated, and the ground state reconstruction due to fluctuations is described phenomenologically, by means of a biquadratic term.
Abstract: is a quantum triangular antiferromagnet, ferromagnetically stacked, with an incommensurate (IC) structure due to a Dzyaloshinskii-Moriya interaction. Because of the classical degeneracy caused by the frustration, fluctuations in have extraordinarily large effects, such as the phase transition in longitudinal magnetic field (normal to the planes, parallel to the IC wavenumber q) and the plateau in q in transverse field (perpendicular to q). We argue that fluctuations are responsible also for the new IC phase discovered in transverse field near the Neel temperature , by Werner et al (Werner T, Weber H B, Wosnitza J, Kelnberger A, Meschke M, Schotte U, Stuser N, Ding Y and Winkelmann M 1997 Solid State Commun. 102 609). We develop and analyse the corresponding minimal Landau theory; the ground-state reconstruction due to fluctuations is described phenomenologically, by means of a biquadratic term. The Landau theory gives two IC phases, one familiar from previous studies; the properties of the new IC phase, which occupies a pocket of the temperature-field phase diagram near , agree qualitatively with those of the new phase found experimentally.
19 citations
TL;DR: In this paper, a single phase Mn 5 Ge 3 ribbons were successfully synthesized by single roller melt-spinning method followed by an annealing procedure at 800°C for 1h.
19 citations
01 Jan 1999
TL;DR: Two new elementary proofs are given of Landau's Theorem on necessary and sufficient conditions for a sequence of integers to be the score sequence for some tournament, and both proofs are constructive, so they each provide an algorithm for obtaining a tournament realizing a sequence satisfyingLandau's conditions.
Abstract: Two new elementary proofs are given of Landau's Theorem on necessary and sufficient conditions for a sequence of integers to be the score sequence for some tournament. The first is related to existing proofs by majorization, but it avoids depending on any facts about majorization. The second is natural and direct. Both proofs are constructive, so they each provide an algorithm for obtaining a tournament realizing a sequence satisfying Landau's conditions.
19 citations
TL;DR: It is shown that pulses in the complete quintic one-dimensional Ginzburg–Landau equation with complex coefficients appear through a saddle-node bifurcation which is determined analytically through a suitable approximation of the explicit form of the pulses.
Abstract: It is shown that pulses in the complete quintic one-dimensional Ginzburg–Landau equation with complex coefficients appear through a saddle-node bifurcation which is determined analytically through a suitable approximation of the explicit form of the pulses The results are in excellent agreement with direct numerical simulations
19 citations