911 research outputs found
Solution of Some Integrable One-Dimensional Quantum Systems
In this paper, we investigate a family of one-dimensional multi-component
quantum many-body systems. The interaction is an exchange interaction based on
the familiar family of integrable systems which includes the inverse square
potential. We show these systems to be integrable, and exploit this
integrability to completely determine the spectrum including degeneracy, and
thus the thermodynamics. The periodic inverse square case is worked out
explicitly. Next, we show that in the limit of strong interaction the "spin"
degrees of freedom decouple. Taking this limit for our example, we obtain a
complete solution to a lattice system introduced recently by Shastry, and
Haldane; our solution reproduces the numerical results. Finally, we emphasize
the simple explanation for the high multiplicities found in this model
Extracting Hidden Symmetry from the Energy Spectrum
In this paper we revisit the problem of finding hidden symmetries in quantum
mechanical systems. Our interest in this problem was renewed by nontrivial
degeneracies of a simple spin Hamiltonian used to model spin relaxation in
alkali-metal vapors. We consider this spin Hamiltonian in detail and use this
example to outline a general approach to finding symmetries when eigenvalues
and eigenstates of the Hamiltonian are known. We extract all nontrivial
symmetries responsible for the degeneracy and show that the symmetry group of
the Hamiltonian is SU(2). The symmetry operators have a simple meaning which
becomes transparent in the limit of large spin. As an additional example we
apply the method to the Hydrogen atom.Comment: 14 pages, 1 figure. A minor typo correcte
Extremely Correlated Fermi Liquids
We present the theory of an extremely correlated Fermi liquid (ECFL) with
. This liquid has an underlying Fermi liquid (FL) Greens function
that is further caparisoned. The theory leads to two parallel hierarchies of
equations that permit iterative approximations in a certain parameter.
Preliminary results for the spectral functions display a broad background and a
distinct dependent left skew. An important energy scale
emerges as the average inelasticity of the FL Greens function, and influences
the photoemission spectra profoundly. A duality is identified wherein an
apparent loss of coherence of the ECFL results from an excessively sharp FL.Comment: Published version, 3 figures; Published July 29, 201
Electron concentration effects on the Shastry-Sutherland phase stability in Ce_{2-x}Pd_{2+y}In_{1-z} solid solutions
The stability of a Shastry-Sutherland ShSu phase as a function of electron
concentration is investigated through the field dependence of thermal and
magnetic properties of the solid solution Ce_{2-x}Pd_{2+y}In_{1-z} in the
antiferromagnetic branch. In these alloys the electronic (holes) variation is
realized by increasing concentration. The AF transition T_M decreases from
3.5K to 2.8K as concentration increases from y=0.2 to y=0.4. By applying
magnetic field, the ShSu phase is suppressed once the field induced
ferromagnetic polarization takes over at a critical field B_{cr} which
increases with content. A detailed analysis around the critical point
reveals a structure in the maximum of the dM/dB derivative, which is related
with incipient steps in the magnetization M(B) as predicted by the theory for
the ShSu lattice. The crossing of M(B) isotherms, observed in ShSu prototype
compounds, is also analyzed. The effect of substitution by is
interpreted as an increase of the number of 'holes' in the conduction band and
results in a unique parameter able to describe the variation of the magnetic
properties along the studied range of concentration.Comment: 8 pages, 11 figure
Ising pyrochlore magnets: Low temperature properties, ice rules and beyond
Pyrochlore magnets are candidates for spin-ice behavior. We present
theoretical simulations of relevance for the pyrochlore family R2Ti2O7 (R= rare
earth) supported by magnetothermal measurements on selected systems. By
considering long ranged dipole-dipole as well as short-ranged superexchange
interactions we get three distinct behaviours: (i) an ordered doubly degenerate
state, (ii) a highly disordered state with a broad transition to paramagnetism,
(iii) a partially ordered state with a sharp transition to paramagnetism. Thus
these competing interactions can induce behaviour very different from
conventional ``spin ice''. Closely corresponding behaviour is seen in the real
compounds---in particular Ho2Ti2O7 corresponds to case (iii) which has not been
discussed before, rather than (ii) as suggested earlier.Comment: 5 pages revtex, 4 figures; some revisions, additional data,
additional co-authors and a changed title. Basic ideas of paper remain the
same but those who downloaded the original version are requested to get this
more complete versio
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