2,749 research outputs found
The Achievements of Trooper Mulloy
In the summer of 1900 Lorne Mulloy, a wounded Canadian soldier serving with the second Canadian contingent in South Africa, wrote from a military hospital in Johannesburg to his family about serious wounds to his eyes received in battle: “I have not experienced even the faintest sensation of light since that shot was fired. My left eye is totally destroyed and my right one is so badly injured that it is like a man halting between life and death undecided to advance or retreat.” Although totally blind because of these wounds Mulloy went on to obtain three university degrees, and became a respected professor and speaker on political issues in Canada and Britain and a prominent figure in his local community. His life is a remarkable story of achievement in the face of adversity
Localization Lifetime of a Many-Body System with Periodic Constructed Disorder
We show that, in a many-body system, all particles can be strongly confined
to the initially occupied sites for a time that scales as a high power of the
ratio of the bandwidth of site energies to the hopping amplitude. Such
time-domain formulation is complementary to the formulation of the many-body
localization of all stationary states with a large localization length. The
long localization lifetime is achieved by constructing a periodic sequence of
site energies with a large period in a one-dimensional chain. The scaling of
the localization lifetime is independent of the number of particles for a broad
range of the coupling strength. The analytical results are confirmed by
numerical calculations
Interplay between Magnetic and Vestigial Nematic Orders in the Layered - Classical Heisenberg Model
We study the layered - classical Heisenberg model on the square
lattice using a self-consistent bond theory. We derive the phase diagram for
fixed as a function of temperature , and interplane coupling
. Broad regions of (anti)ferromagnetic and stripe order are found, and are
separated by a first-order transition near (in units of
). Within the stripe phase the magnetic and vestigial nematic
transitions occur simultaneously in first-order fashion for strong . For
weaker there is in addition, for , an intermediate
regime of split transitions implying a finite temperature region with nematic
order but no long-range stripe magnetic order. In this split regime, the order
of the transitions depends sensitively on the deviation from and
, with split second-order transitions predominating for . We find that the value of depends weakly on the
interplane coupling and is just slightly larger than for . In contrast the value of increases quickly from at
as the interplane coupling is further reduced. In
addition, the magnetic correlation length is shown to directly depend on the
nematic order parameter and thus exhibits a sharp increase (or jump) upon
entering the nematic phase. Our results are broadly consistent with predictions
based on itinerant electron models of the iron-based superconductors in the
normal-state, and thus help substantiate a classical spin framework for
providing a phenomenological description of their magnetic properties.Comment: 13 pages, 20 figure
Nematic Bond Theory of Heisenberg Helimagnets
We study classical two-dimensional frustrated Heisenberg models with
generically incommensurate groundstates. A new theory for the spin-nematic
"order by disorder" transition is developed based on the self-consistent
determination of the effective exchange coupling bonds. In our approach,
fluctuations of the constraint field imposing conservation of the local
magnetic moment drive nematicity at low temperatures. The critical temperature
is found to be highly sensitive to the peak helimagnetic wavevector, and
vanishes continuously when approaching rotation symmetric Lifshitz points.
Transitions between symmetry distinct nematic orders may occur by tuning the
exchange parameters, leading to lines of bicritical points.Comment: 4 pages, 4 figure
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