44,789 research outputs found
NMR relaxation rate and dynamical structure factors in nematic and multipolar liquids of frustrated spin chains under magnetic fields
Recently, it has been shown that spin nematic (quadrupolar) or higher
multipolar correlation functions exhibit a quasi long-range order in the wide
region of the field-induced Tomonaga-Luttinger-liquid (TLL) phase in spin-1/2
zigzag chains. In this paper, we point out that the temperature dependence of
the NMR relaxation rate 1/T_1 in these multipolar TLLs is qualitatively
different from that in more conventional TLLs of one-dimensional quantum
magnets (e.g., the spin-1/2 Heisenberg chain); 1/T_1 decreases with lowering
temperature in multipolar TLL. We also discuss low-energy features in spin
dynamical structure factors which are characteristic of the multipolar TLL
phases.Comment: 4+epsilon pages, 2 figures, published versio
In search of multipolar order on the Penrose tiling
Based on Monte Carlo calculations, multipolar ordering on the Penrose tiling,
relevant for two-dimensional molecular adsorbates on quasicrystalline surfaces
and for nanomagnetic arrays, has been analyzed. These initial investigations
are restricted to multipolar rotors of rank one through four - described by
spherical harmonics Ylm with l=1...4 and restricted to m=0 - positioned on the
vertices of the rhombic Penrose tiling. At first sight, the ground states of
odd-parity multipoles seem to exhibit long-range multipolar order, indicated by
the appearance of a superstructure in the form of the decagonal
Hexagon-Boat-Star tiling, in agreement with previous investigations of dipolar
systems. Yet careful analysis establishes that long-range multipolar order is
absent in all cases investigated here, and only short-range order exists. This
result should be taken as a warning for any future analysis of order in either
real or simulated arrangements of multipoles on quasiperiodic templates
Multipolar Planetary Nebulae: Not as Geometrically Diversified as Thought
Planetary nebulae (PNe) have diverse morphological shapes, including
point-symmetric and multipolar structures. Many PNe also have complicated
internal structures such as torus, lobes, knots, and ansae. A complete
accounting of all the morphological structures through physical models is
difficult. A first step toward such an understanding is to derive the true
three-dimensional structure of the nebulae. In this paper, we show that a
multipolar nebula with three pairs of lobes can explain many of such features,
if orientation and sensitivity effects are taken into account. Using only six
parameters - the inclination and position angles of each pair - we are able to
simulate the observed images of 20 PNe with complex structures. We suggest that
the multipolar structure is an intrinsic structure of PNe and the statistics of
multipolar PNe has been severely underestimated in the past.Comment: 36 pages, 5 figures, 2 table
Emergent multipolar spin correlations in a fluctuating spiral - The frustrated ferromagnetic S=1/2 Heisenberg chain in a magnetic field
We present the phase diagram of the frustrated ferromagnetic S=1/2 Heisenberg
J_1-J_2 chain in a magnetic field, obtained by large scale exact
diagonalizations and density matrix renormalization group simulations. A vector
chirally ordered state, metamagnetic behavior and a sequence of spin-multipolar
Luttinger liquid phases up to hexadecupolar kind are found. We provide
numerical evidence for a locking mechanism, which can drive spiral states
towards spin-multipolar phases, such as quadrupolar or octupolar phases. Our
results also shed light on previously discovered spin-multipolar phases in
two-dimensional quantum magnets in a magnetic field.Comment: 4+ pages, 4 figure
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