12,823 research outputs found
Phase diagram of the spin-1/2 triangular J1-J2 Heisenberg model on a three-leg cylinder
We study the phase diagram of the frustrated Heisenberg model on the triangular lattice with nearest- and next-nearest-neighbor spin-exchange coupling, on three-leg ladders. Using the density-matrix renormalization-group method, we obtain the complete phase diagram of the model, which includes quasi-long-range 120° and columnar order, and a Majumdar-Ghosh phase with short-ranged correlations. All these phases are nonchiral and planar. We also identify the nature of phase transitions
Haldane phase in the hubbard model at 2/3-filling for the organic molecular compound Mo3 S7 (dmit)3
We report the discovery of a correlated insulator with a bulk gap at 2/3 filling in a geometrically frustrated Hubbard model that describes the low-energy physics of Mo3S7(dmit)(3). This is very different from the Mott insulator expected at half-filling. We show that the insulating phase, which persists even for very weak electron-electron interactions (U), is adiabatically connected to the Haldane phase and is consistent with experiments on Mo3S7(dmit)(3)
Critical exponents and phase transition in gold nuclei fragmentation at energies 10.6 and 4.0 GeV/nucleon
An attempt to extract critical exponents gamma, beta and tau from data on
gold nuclei fragmentation due to interactions with nuclear emulsion at energies
4.0 A GeV and 10.6 A GeV is presented. Based on analysis of Campi's 2nd charge
moments, two subsets of data at each energy are selected from the inclusive
data, corresponding to 'liquid' and 'gas' phases. The extracted values of
critical exponents from the selected data sets are in agreement with
predictions of 'liquid-gas' model of phase transition.Comment: 21 pages, 15 figure
Tunable dipolar magnetism in high-spin molecular clusters
We report on the Fe17 high-spin molecular cluster and show that this system
is an exemplification of nanostructured dipolar magnetism. Each Fe17 molecule,
with spin S=35/2 and axial anisotropy as small as D=-0.02K, is the magnetic
unit that can be chemically arranged in different packing crystals whilst
preserving both spin ground-state and anisotropy. For every configuration,
molecular spins are correlated only by dipolar interactions. The ensuing
interplay between dipolar energy and anisotropy gives rise to macroscopic
behaviors ranging from superparamagnetism to long-range magnetic order at
temperatures below 1K.Comment: Replaced with version accepted for publication in Physical Review
Letter
Competition between disorder and exchange splitting in superconducting ZrZn_2
We propose a simple picture for the occurrence of superconductivity and the
pressure dependence of the superconducting critical temperature, T_{SC}, in
ZrZn_2. According to our hypothesis the pairing potential is independent of
pressure, but the exchange splitting, E_{xc}, leads to a pressure dependence in
the (spin dependent) density of states at the Fermi level,
D_\sigma(\epsilon_F). Assuming p-wave pairing T_{SC} is dependent on
D_\sigma(\epsilon_F) which ensures that, in the absence of non-magnetic
impurities, T_{SC} decreases as pressure is applied until it reaches a minimum
in the paramagnetic state. Disorder reduces this minimum to zero, this gives
the illusion that the superconductivity disappears at the same pressure as
ferromagnetism does.Comment: 7 pages, 4 figures, submitted to J. Phys. Cond. Ma
Photometric Decomposition of Barred Galaxies
We present a non-parametric method for decomposition of the light of disk
galaxies into disk, bulge and bar components. We have developed and tested the
method on a sample of 68 disk galaxies for which we have acquired I-band
photometry. The separation of disk and bar light relies on the single
assumption that the bar is a straight feature with a different ellipticity and
position angle from that of the projected disk. We here present the basic
method, but recognise that it can be significantly refined. We identify bars in
only 47% of the more nearly face-on galaxies in our sample. The fraction of
light in the bar has a broad range from 1.3% to 40% of the total galaxy light.
If low-luminosity galaxies have more dominant halos, and if halos contribute to
bar stability, the luminosity functions of barred and unbarred galaxies should
differ markedly; while our sample is small, we find only a slight difference of
low significance.Comment: Accepted to appear in AJ, 36 pages, 9 figures, full on-line figures
available at http://www.physics.rutgers.edu/~sellwood/Reese.htm
Magnetic field structure at the diamagnetic cavity boundary (Numerical simulations)
Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/95513/1/grl13492.pd
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