scholarly journals Structure and phase transitions in A -site ordered RBaMn2O6 ( R=Pr,Nd ) perovskites with a polar ground state

2021 ◽  
Vol 103 (6) ◽  
Author(s):  
J. Blasco ◽  
G. Subías ◽  
M. L. Sanjuán ◽  
J. L. García-Muñoz ◽  
F. Fauth ◽  
...  
Keyword(s):  
Phase Transitions ◽  
Ground State ◽  
A Site

Crystal Structures and Phase Transitions in A-Site Deficient Perovskites Ln1/3TaO3

2008 ◽  
Vol 20 (21) ◽  
pp. 6666-6676 ◽  
Author(s):  
Qingdi Zhou ◽  
Paul J. Saines ◽  
Neeraj Sharma ◽  
Jimmy Ting ◽  
Brendan J. Kennedy ◽  
...  
Keyword(s):  
Phase Transitions ◽  
Crystal Structures ◽  
A Site

scholarly journals Unconventional phase transitions in strongly anisotropic 2D (pseudo)spin systems

2018 ◽  
Vol 185 ◽  
pp. 08006
Author(s):  
Vitaly Konev ◽  
Evgeny Vasinovich ◽  
Vasily Ulitko ◽  
Yury Panov ◽  
Alexander Moskvin
Keyword(s):  
Magnetic Field ◽  
Monte Carlo ◽  
Phase Transitions ◽  
Ground State ◽  
Quantum Monte Carlo ◽  
Mean Field ◽  
Spin Systems ◽  
Field Approach ◽  
Generalized Mean

We have applied a generalized mean-field approach and quantum Monte-Carlo technique for the model 2D S = 1 (pseudo)spin system to find the ground state phase with its evolution under application of the (pseudo)magnetic field. The comparison of the two methods allows us to clearly demonstrate the role of quantum effects. Special attention is given to the role played by an effective single-ion anisotropy ("on-site correlation").

SPECTRAL PROPERTIES AND SYMMETRIES OF DOUBLE COVERINGS OF GRAPHS WITH APPLICATIONS TO SUPERCONDUCTIVITY

2005 ◽  
Vol 15 (02) ◽  
pp. 301-324
Author(s):  
JACOB RUBINSTEIN ◽  
MICHELLE SCHATZMAN
Keyword(s):  
Magnetic Field ◽  
Phase Transition ◽  
Phase Transitions ◽  
Ground State ◽  
Spectral Properties ◽  
Embedded Graph ◽  
Symmetry Constraints ◽  
The Laplace Operator ◽  
The Magnetic Field ◽  
Double Coverings

Let M be a planar embedded graph, and let [Formula: see text] be its double covering. We count the multiplicity of the ground states of the Laplace operator on [Formula: see text] under certain symmetry constraints. The examples of interest for us are ladder-like graphs made out of n, identical rectangles. We find that in the case of an odd n, the multiplicity of the ground state is 2, and if n, is even, the ground state is simple. This result gives an answer to a conjecture by Parks on the type of phase transitions that can occur in a superconducting ladder: Parks conjectured that in the case when the magnetic field is one half fluxoid per rectangle, the phase transition would be continuous in the case of a ladder made out of two rectangles. Our result indeed implies Parks conjecture and generalizes it to any even ladder. The mathematics of this paper is a mixture of topology, symmetry arguments and comparison theorem between the eigenvalues of Laplace operators on graphs with well chosen boundary conditions.

QUANTUM PHASE TRANSITIONS AND ENTANGLEMENT IN J1–J2 MODEL

2004 ◽  
Vol 15 (08) ◽  
pp. 1095-1103 ◽  
Author(s):  
RECEP ERYIĞIT ◽  
RESUL ERYIĞIT ◽  
YIĞIT GÜNDÜÇ
Keyword(s):  
Phase Transition ◽  
Phase Diagram ◽  
Phase Transitions ◽  
Ground State ◽  
Abrupt Change ◽  
Quantum Phase Transitions ◽  
Nearest Neighbors ◽  
Competing Interactions ◽  
One Dimensional ◽  
Transition Points

We study ground state pairwise entanglement within one-dimensional spin-1/2 antiferromagnetic J1–J2 model with competing interactions. Contrary to some claims we found that frustration does not increase entanglement. Concurrence of nearest and next nearest neighbors are found to show abrupt change at phase transition points. We also show that the concurrence can be used to classify the phase diagram of the model in anisotropy–frustration plane.

Investigation of the structure and phase transitions in the novel A-site substituted distorted perovskite compound Na0.5Bi0.5TiO3

2002 ◽  
Vol 58 (2) ◽  
pp. 168-178 ◽  
Author(s):  
G. O. Jones ◽  
P. A. Thomas
Keyword(s):  
Phase Transitions ◽  
Phase Space ◽  
Profile Analysis ◽  
Second Harmonic ◽  
Rhombohedral Phase ◽  
Polar Axis ◽  
Temperature Limit ◽  
Space Group ◽  
Systematic Behaviour ◽  
A Site

Rietveld neutron powder profile analysis of the compound Na0.5Bi0.5TiO3 (NBT) is reported over the temperature range 5–873 K. The sequence of phase transitions from the high-temperature prototypic cubic structure (above 813 K), to one of tetragonal (673–773 K) and then rhombohedral structures (5–528 K) has been established. Coexisting tetragonal/cubic (773–813 K) and rhombohedral/tetragonal (with an upper temperature limit of 145 K between 528 and 673 K) phases have also been observed. Refinements have revealed that the rhombohedral phase, space group R3c, with a H = 5.4887 (2), c H = 13.5048 (8) Å, V = 352.33 (3) Å3, Z = 6 and D x = 5.99 Mg m−3, exhibits an antiphase, a − a − a − oxygen tilt system, ω = 8.24 (4)°, with parallel cation displacements at room temperature. The tetragonal phase, space group P4bm, with a T = 5.5179 (2), c T = 3.9073 (2) Å, V = 118.96 (1) Å3, Z = 2 and D x = 5.91 Mg m−3, possesses an unusual combination of in-phase, a 0 a 0 c + oxygen octahedra tilts, ω = 3.06 (2)°, and antiparallel cation displacements along the polar axis. General trends of cation displacements and the various deviations of the octahedral network from the prototypic cubic perovskite structure have been established and their systematic behaviour with temperature is reported. An investigation of phase transition behaviour using second harmonic generation (SHG) to establish the centrosymmetric or non-centrosymmetric nature of the various phases is also reported.

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