Antiferromagnet lattice arrangements influence phase transitions

Date:
September 28, 2020
Source:
Springer
Summary:
New research reveals that the nature of the boundary at which
an antiferromagnet transitions to a state of disorder slightly
depends on the geometry of its lattice arrangement.



FULL STORY ==========================================================================
New research published in EPJ B reveals that the nature of the boundary
at which an antiferromagnet transitions to a state of disorder slightly
depends on the geometry of its lattice arrangement.


========================================================================== Calculations involving 'imaginary' magnetic fields show how the
transitioning behaviours of antiferromagnets are subtly shaped by their
lattice arrangements.

Antiferromagnets contain orderly lattices of atoms and molecules, whose magnetic moments are always pointed in exactly opposite directions to
those of their neighbours.

These materials are driven to transition to other, more disorderly quantum states of matter, or 'phases,' by the quantum fluctuations of their
atoms and molecules -- but so far, the precise nature of this process
hasn't been fully explored. Through new research published in EPJ B,
Yoshihiro Nishiyama at Okayama University in Japan has found that the
nature of the boundary at which this transition occurs depends on the
geometry of an antiferromagnet's lattice arrangement.

Nishiyama's discovery could enable physicists to apply antiferromagnets
in a wider variety of contexts within material and quantum physics. His calculations concerned the 'fidelity' of the materials, which refers in
this case to the degree of overlap between the ground states of their interacting lattice components. Furthermore, the fidelity 'susceptibility' describes the degree to which this overlap is influenced by an applied
magnetic field. Since susceptibility is driven by quantum fluctuations,
it can be expressed within the language of statistical mechanics --
describing how macroscopic observations can arise from the combined
influences of many microscopic vibrations.

This makes it a useful probe of how antiferromagnet phase transitions
are driven by quantum fluctuations.

Using advanced mathematical techniques, Nishiyama calculated how the susceptibility is affected by 'imaginary' magnetic fields -- which do
not influence the physical world, but are crucial for describing the statistical mechanics of phase transitions. By applying this technique to
an antiferromagnet arranged in a honeycomb lattice, he revealed that the transition between orderly, anti-aligned magnetic moments, and a state
of disorder, occurs across a boundary with a different shape to that
associated with the same transition in a square lattice. By clarifying how
the geometric arrangement of lattice components has a subtle influence
on this point of transition, Nishiyama's work could advance physicists' understanding of the statistical mechanics of antiferromagnets.


========================================================================== Story Source: Materials provided by Springer. Note: Content may be edited
for style and length.


========================================================================== Journal Reference:
1. Yoshihiro Nishiyama. Fidelity-susceptibility analysis of the
honeycomb-
lattice Ising antiferromagnet under the imaginary magnetic
field. The European Physical Journal B, 2020; 93 (9) DOI:
10.1140/epjb/e2020-10264-5 ==========================================================================

Link to news story: https://www.sciencedaily.com/releases/2020/09/200928125014.htm

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