The free energy of solitons coupled to fermions: absence of a gradient expansion at zero temperature due to bound states

1992 ◽  
Vol 25 (6) ◽  
pp. 1593-1604 ◽  
Author(s):  
D Waxman ◽  
G Williams
1990 ◽  
Vol 04 (01) ◽  
pp. 143-150 ◽  
Author(s):  
CLAUDIO PROCESI ◽  
BRUNELLO TIROZZI

We describe the properties of the free energy of the Hopfield model with a finite number of patterns and describe its dynamic at zero temperature in the space of overlaps in the thermodynamic limit.


2000 ◽  
Vol 64 (2) ◽  
pp. 311-317 ◽  
Author(s):  
M. C. Warren ◽  
M. T. Dove ◽  
S. A. T. Redfern

AbstractAt high temperature, MgAl2O4 spinel is stabilized by disorder of Mg and Al between octahedral and tetrahedral sites. This behaviour has been measured up to 1700 K in recent neutron experiments, but the extrapolation of subsequently fitted thermodynamic models is not reliable. First principles simulation of the electronic structure of such minerals can in principle accurately predict disorder, but would require unfeasibly large computing resources. We have instead parameterized on-site and short-ranged cluster potentials using a small number of electronic structure simulations at zero temperature. These potentials were then used in large-scale statistical simulations at finite temperatures to predict disordering thermodynamics beyond the range of experimental measurements. Within the temperature range of the experiment, good agreement is obtained for the degree of order. The entropy and free energy are calculated and compared to those from macroscopic models.


2020 ◽  
Vol 11 (1) ◽  
Author(s):  
S. Autti ◽  
S. L. Ahlstrom ◽  
R. P. Haley ◽  
A. Jennings ◽  
G. R. Pickett ◽  
...  

Abstract The ground state of a fermionic condensate is well protected against perturbations in the presence of an isotropic gap. Regions of gap suppression, surfaces and vortex cores which host Andreev-bound states, seemingly lift that strict protection. Here we show that in superfluid 3He the role of bound states is more subtle: when a macroscopic object moves in the superfluid at velocities exceeding the Landau critical velocity, little to no bulk pair breaking takes place, while the damping observed originates from the bound states covering the moving object. We identify two separate timescales that govern the bound state dynamics, one of them much longer than theoretically anticipated, and show that the bound states do not interact with bulk excitations.


2013 ◽  
Vol 27 (08) ◽  
pp. 1350028 ◽  
Author(s):  
NABYENDU DAS

Here a recently observed weak first order transition in doped SrTiO 3 [Taniguchi, Itoh and Yagi, Phys. Rev. Lett.99, 017602 (2007)] is argued to be a consequence of the coupling between strain and order parameter fluctuations. Starting with a semi-microscopic action, and using renormalization group equations for vertices, we write the free energy of such a system. This fluctuation renormalized free energy is then used to discuss the possibility of first order transition at zero temperature as well as at finite temperature. An asymptotic analysis predicts small but a finite discontinuity in the order parameter near a mean field quantum critical point at zero temperature. In case of finite temperature transition, near quantum critical point such a possibility is found to be extremely weak. Results are in accord with some experimental findings on quantum paraelectrics such as SrTiO 3 and KTaO 3.


1993 ◽  
Vol 394 (2) ◽  
pp. 423-442 ◽  
Author(s):  
A.A. Bytsenko ◽  
E. Elizalde ◽  
S.D. Odintsov ◽  
S. Zerbini

2008 ◽  
Vol 64 (2) ◽  
pp. 131-143 ◽  
Author(s):  
Patrick H. J. Mercier ◽  
Yvon Le Page

The well known 36 distinguishable transformations between adjacent kaolin layers are split into 20 energetically distinguishable transformations (EDT) and 16 enantiomorphic transformations, hereafter denoted EDT*. For infinitesimal energy contribution of interactions between non-adjacent layers, the lowest-energy models must result from either (a) repeated application of an EDT or (b) alternate application of an EDT and its EDT*. All modeling, quantum input preparation and interpretation was performed with Materials Toolkit, and quantum optimizations with VASP. Kaolinite and dickite are the lowest-energy models at zero temperature and pressure, whereas nacrite and HP-dickite are the lowest-enthalpy models under moderate pressures based on a rough enthalpy/pressure graph built from numbers given in the supplementary tables. Minor temperature dependence of this calculated 0 K graph would explain the bulk of the current observations regarding synthesis, diagenesis and transformation of kaolin minerals. Other stackings that we list have energies so competitive that they might crystallize at ambient pressure. A homometric pair of energetically distinguishable ideal models, one of them for nacrite, is exposed. The printed experimental structure of nacrite correctly corresponds to the stable member of the pair. In our opinion, all recent literature measurements of the free energy of bulk kaolinite are too negative by ∼ 15 kJ mol−1 for some unknown reason.


1974 ◽  
Vol 52 (1) ◽  
pp. 33-39 ◽  
Author(s):  
D. A. Pink ◽  
R. Ballard

We have investigated the two-magnon bound state spectrum of a ferromagnetically ordered system for which the Hamiltonian contains an anisotropic bilinear exchange term, an anisotropic biquadratic exchange term, and a single-ion anisotropy term. The bound states, labelled by a wave vector q which we have taken to be in the [111] direction, were calculated by using zero-temperature Green functions. The principal results are: (i) the existence of single-ion bound states in the absence of single-ion anisotropy and conversely, their absence in the presence of such anisotropy, in contrast to the case in which the exchange interactions are isotropic; (ii) the appearance of an S mode for values of q, [Formula: see text]; (iii) the ordering of bound states for isotropic exchange interactions wherein the S0 mode lies below the S1-mode, D-mode pair and where the S1 mode lies below (above) the D mode if they lie below (above) the band, no longer holds.


1994 ◽  
Vol 72 (1-2) ◽  
pp. 1-6 ◽  
Author(s):  
E. Dunlap ◽  
D. J. W. Geldart

Nonlocal exchange contributions to the free energy of a weakly inhomogeneous many-fermion system at finite temperature are obtained to first order in the interparticle interaction. Explicit representations are given for the second-order gradient coefficient Bx (n(r); T). These results apply for arbitrary velocity-independent interparticle interaction and arbitrary temperature.


1999 ◽  
Vol 59 (14) ◽  
pp. 9545-9557 ◽  
Author(s):  
Šimon Kos ◽  
Michael Stone

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