scholarly journals Zero-temperature transition and correlation-length exponent of the frustratedXYmodel on a honeycomb lattice

2012 ◽  
Vol 85 (5) ◽  
Author(s):  
Enzo Granato
Keyword(s):  
Correlation Length ◽  
Honeycomb Lattice ◽  
Zero Temperature ◽  
Temperature Transition

scholarly journals Holographic quarkyonic matter

2020 ◽  
Vol 2020 (9) ◽  
Author(s):  
Nicolas Kovensky ◽  
Andreas Schmitt
Keyword(s):  
Nuclear Matter ◽  
Real World ◽  
Quark Matter ◽  
Chiral Limit ◽  
Pion Mass ◽  
Zero Temperature ◽  
Temperature Transition ◽  
Physical Point ◽  
First Order ◽  
Chemical Potentials

Abstract We point out a new configuration in the Witten-Sakai-Sugimoto model, allowing baryons in the pointlike approximation to coexist with fundamental quarks. The resulting phase is a holographic realization of quarkyonic matter, which is predicted to occur in QCD at a large number of colors, and possibly plays a role in real-world QCD as well. We find that holographic quarkyonic matter is chirally symmetric and that, for large baryon chemical potentials, it is energetically preferred over pure nuclear matter and over pure quark matter. The zero-temperature transition from nuclear matter to the quarkyonic phase is of first order in the chiral limit and for a realistic pion mass. For pion masses far beyond the physical point we observe a quark-hadron continuity due to the presence of quarkyonic matter.

SPIN TEXTURES AND RANDOM FIELDS IN DIRTY QUANTUM HALL FERROMAGNETS

2006 ◽  
Vol 20 (19) ◽  
pp. 2785-2794
Author(s):  
J. T. CHALKER
Keyword(s):  
Ground State ◽  
Random Fields ◽  
Order Parameter ◽  
Magnetic Order ◽  
Quantum Hall ◽  
Quenched Disorder ◽  
Zero Temperature ◽  
Temperature Transition ◽  
Strong Disorder ◽  
Second Category

Dirty quantum Hall ferromagnets (QHFMs) provide a setting both for new problems in the theory of magnetism with quenched disorder, and for new realisations of old problems. In the first category, the fact that spin textures in Heisenberg QHFMs carry charge leads to a coupling between charged impurities and magnetic order. This coupling drives a zero-temperature transition between a ferromagnet at low disorder and a spin glass at strong disorder, and controls screening and the nature of excitations in the disorder-dominated ground state. In the second category, random fields coupling linearly to the order parameter appear in some Ising QHFMs, and transport measurements appear to indicate field-induced domain states at low temperature.

EXTREME TYPE II SUPERCONDUCTORS: UNIVERSAL PROPERTIES AND TRENDS

1994 ◽  
Vol 08 (05) ◽  
pp. 487-528 ◽  
Author(s):  
T. SCHNEIDER ◽  
H. KELLER
Keyword(s):  
Relaxation Rate ◽  
Penetration Depth ◽  
Correlation Length ◽  
Phase Correlation ◽  
Zero Temperature ◽  
Condensate Density ◽  
Type Ii Superconductors ◽  
Extreme Type ◽  
Critical Amplitudes ◽  
Two Fluid

We review and analyze experiment results of the specific heat, the muon–spin rotation (μSR) relaxation rate and the fluctuation contributions to the magnetization and dc conductivity of extreme type II superconductors from the point of view of critical phenomena. Our estimates of critical exponents and amplitudes, the measured scaling behavior, the consistencies with the universal relations between the critical amplitudes and the decrease of the transition temperature (T c ) with decreasing thickness, which corresponds to a dimensional crossover from 3d and 2d xy critical behavior, provide considerable evidence for a three-dimensional xy critical point. The estimated volume of the critical correlation length amplitudes turns out to be comparable to that in super-fluid Helium and is several orders of magnitude smaller than in BCS superconductors. Moreover, motivated by the Uemura plot, which relates the measured T c to the zero temperature μSR relaxation rate, and by the hyperuniversal relation between T c and critical amplitudes of the London penetration depth and phase correlation length, we propose a simple "universal" scaling ansatz, where the plot of the rescaled transition temperature versus rescaled μSR relaxation rate should fall on a single parabola. Our analysis of the μSR data reveals excellent agreement with this scaling ansatz for a large class of cuprate and Chevrel-phase superconductors. The resulting dependence of T c on the zero-temperature "condensate density" is then used to explore universal trends in the pressure (α) and isotope (β) coefficients. In good agreement with experiment we find that α and β fall into common T c -α and T c -β regions, respectively, forming two branches, one for systems with positive and the other for compounds with negative pressure or isotope coefficient. The two branches merge at the maximum T c where the coefficients vanish and the magnitude of the coefficients increases with decreasing T c . The "universal" scaling ansatz also implies that the critical amplitudes of the penetration depth and phase correlation length are related to the zero temperature condensate density. This quantity is also related to the hole concentration. Finally we discuss the temperature dependence of the penetration depth. μSR measurements indicate that for various cuprates the temperature dependence for 0 < T < T c appears to be bounded by the two-fluid model and the dilute charged Bose gas behaviors, respectively. Consistent with the dependence of T c on the zero temperature condensate density, compounds with high T c 's turn out to be closer to two-fluid behavior, while compounds with decreasing T c and in turn with lower condensate density clearly reveal the crossover to the dilute gas limit. These trends combined with T → 0 point uniquely to Bose condensation of interacting and weakly charged pairs as the mechanism that drives the transition.

GRAPHICAL SOLUTION OF THE ISING MODEL ON HONEYCOMB LATTICE

2009 ◽  
Vol 23 (03) ◽  
pp. 395-401 ◽  
Author(s):  
S. AKBAR JAFARI
Keyword(s):  
Ising Model ◽  
Partition Function ◽  
Valence Bond ◽  
Honeycomb Lattice ◽  
Zero Temperature ◽  
Graphical Solution ◽  
Resonating Valence Bond

In this work, we present a detailed graphical solution for the Ising model on the honeycomb lattice. In view of the mapping between the calculation of the partition function for generalizations of the Ising model and the calculus of resonating valence bond (RVB) states at zero temperature, our calculation may be of relevance to the RVB physics on the honeycomb lattice.

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