3,093 research outputs found
Magnetism, structure, and charge correlation at a pressure-induced Mott-Hubbard insulator-metal transition
We use synchrotron x-ray diffraction and electrical transport under pressure
to probe both the magnetism and the structure of single crystal NiS2 across its
Mott-Hubbard transition. In the insulator, the low-temperature
antiferromagnetic order results from superexchange among correlated electrons
and couples to a (1/2, 1/2, 1/2) superlattice distortion. Applying pressure
suppresses the insulating state, but enhances the magnetism as the
superexchange increases with decreasing lattice constant. By comparing our
results under pressure to previous studies of doped crystals we show that this
dependence of the magnetism on the lattice constant is consistent for both band
broadening and band filling. In the high pressure metallic phase the lattice
symmetry is reduced from cubic to monoclinic, pointing to the primary influence
of charge correlations at the transition. There exists a wide regime of phase
separation that may be a general characteristic of correlated quantum matter.Comment: 5 pages, 3 figure
Modus Vivendi Beyond the Social Contract: Peace, Justice, and Survival in Realist Political Theory
This essay examines the promise of the notion of modus vivendi for realist political theory. I interpret recent theories of modus vivendi as affirming the priority of peace over justice, and explore several ways of making sense of this idea. I proceed to identify two key problems for modus vivendi theory, so conceived. Normatively speaking, it remains unclear how this approach can sustain a realist critique of Rawlsian theorizing about justice while avoiding a Hobbesian endorsement of absolutism. And conceptually, the theory remains wedded to a key feature of social contract theory: political order is conceived as based on agreement. This construes the horizontal tensions among individual or group agents in society as prior to the vertical, authoritative relations between authorities and their subjects. Political authority thereby appears from the start as a solution to societal conflict, rather than a problem in itself. I argue that this way of framing the issue abstracts from political experience. Instead I attempt to rethink the notion of modus vivendi from within the lived experience of political conflict, as oriented not primarily toward peace, but political survival. With this shift of perspective, the idea of modus vivendi shows us, pace Bernard Williams, that the âfirst political questionâ is not how to achieve order and stability, but rather: what can I live with
High sensitivity sensor for moderate pressures
The metal-insulator transition of (V_(0.99)Ti_(0.01))_2O_3 is marked by dramatic changes in the electrical resistivity and the magnetic susceptibility, with a linear pressure variation of -6.06 K/kbar for Pâ¤15 kbar. We propose its use as the sensing element of a manometer in applications where the superconducting transition of soft metals has been traditional
Verwey transition in FeO at high pressure: quantum critical behavior at the onset of metallization
We provide evidence for the existence of a {\em quantum critical point} at
the metallization of magnetite FeO at an applied pressure of GPa. We show that the present ac magnetic susceptibility data
support earlier resistivity data. The Verwey temperature scales with pressure
, with . The resistivity data shows a
temperature dependence , with above and
2.5 at the critical pressure, respectively. This difference in with
pressure is a sign of critical behavior at . The magnetic susceptibility
is smooth near the critical pressure, both at the Verwey transition and near
the ferroelectric anomaly. A comparison with the critical behavior observed in
the Mott-Hubbard and related systems is made.Comment: 5 pages, 5 figure
Personality and Vulnerability to Depression in Stroke Patients
ConclusionsÂż Neuroticism is an important predictor of PSD, a finding that emphasizes the need to take personality into account as a potential vulnerability factor for depression in stroke patients. Research on PSD should aim at delineating the interplay between neurological and psychological factors in the development of PSD.
Relation among concentrations of incorporated Mn atoms, ionized Mn acceptors, and holes in p-(Ga,Mn)As epilayers
The amount of ionized Mn acceptors in various p-type Mn-doped GaAs epilayers
has been evaluated by electrochemical capacitance-voltage measurements, and has
been compared systematically with concentrations of incorporated Mn atoms and
holes for wide range of Mn concentration (10^17 ~ 10^21 cm^-3). Quantitative
assessment of anomalous Hall effect at room temperature is also carried out for
the first time.Comment: 8 pages, 4 figures, tabl
Rearrangement products of 2,2', 4,4', 6,6'-hexamethyl-4,4'-bi-4H-pyran
Call number: LD2668 .T4 1965 H77Master of Scienc
Nonlinear electric field effects at a continuous Mott-Hubbard transition
We characterize the non-Ohmic portion of the conductivity at temperatures T < 1 K in the highly correlated transition metal chalcogenide Ni(S, Se)_2. Pressure tuning of the T = 0 metal-insulator transition reveals the influence of the quantum critical point and permits a direct determination of the dynamical critical exponent z = 2.7_(-0.4)^(+0.3) Within the framework of finite temperature scaling, we find that the spatial correlation length exponent ν and the conductivity exponent Ο differ
Mass enhancement and magnetic order at the Mott-Hubbard transition
We study the evolution with pressure P and band filling y of the heat capacity, Hall coefficient, and resistivity at the approach to the Tâ0 Mott-Hubbard metal-insulator transition (MIT) in highly correlated V_(2-y)O_3. Under P, the electronic effective mass m* diverges at the MIT with a negligible change in carrier concentration n away from half-filling. Conversely, in the doped system m* actually decreases as the MIT is approached, while n increases linearly with y. The low-T magnetic order in the metal helps us deconvolute contributions from charge correlations and spin fluctuations
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