Dynamics of strongly correlated spin systems with reduced dimensionality and/or frustration

2021 ◽  
Vol 47 (6) ◽  
pp. 441-442
Author(s):  
V. S. Kurnosov
Keyword(s):  
Spin Systems ◽  
Strongly Correlated ◽  
Reduced Dimensionality

Microscopic origin of marginal Fermi liquid in strongly correlated spin systems (abstract)

1993 ◽  
Vol 73 (10) ◽  
pp. 6651-6651
Author(s):  
A. P. Protogenov ◽  
D. A. Ryndyk
Keyword(s):  
Fermi Liquid ◽  
Spin Systems ◽  
Strongly Correlated ◽  
Marginal Fermi Liquid ◽  
Microscopic Origin

Theory for dynamic lineshapes of strongly correlated two-spin systems

1989 ◽  
Vol 85 (2) ◽  
pp. 275-293 ◽  
Author(s):  
Nikolas P Benetis ◽  
David J Schneider ◽  
Jack H Freed
Keyword(s):  
Spin Systems ◽  
Strongly Correlated

scholarly journals SEMI-FERMIONIC REPRESENTATION FOR SPIN SYSTEMS UNDER EQUILIBRIUM AND NON-EQUILIBRIUM CONDITIONS

2006 ◽  
Vol 20 (04) ◽  
pp. 381-421 ◽  
Author(s):  
M. N. KISELEV
Keyword(s):  
Spin Systems ◽  
Distribution Functions ◽  
Strongly Correlated ◽  
Imaginary Time ◽  
Special Shape ◽  
Equilibrium Conditions ◽  
Occupation Numbers ◽  
General Derivation ◽  
Fermionic Representation ◽  
Keldysh Technique

We present a general derivation of semi-fermionic representation for spin operators in terms of a bilinear combination of fermions in real and imaginary time formalisms. The constraint on fermionic occupation numbers is fulfilled by means of imaginary Lagrange multipliers resulting in special shape of quasiparticle distribution functions. We show how Schwinger–Keldysh technique for spin operators is constructed with the help of semi-fermions. We demonstrate how the idea of semi-fermionic representation might be extended to the groups possessing dynamic symmetries. We illustrate the application of semi-fermionic representations for various problems of strongly correlated and mesoscopic physics.

scholarly journals Observation of superfluidity in a strongly correlated two-dimensional Fermi gas

Science ◽  
2021 ◽  
Vol 372 (6544) ◽  
pp. 844-846
Author(s):  
Lennart Sobirey ◽  
Niclas Luick ◽  
Markus Bohlen ◽  
Hauke Biss ◽  
Henning Moritz ◽  
...  
Keyword(s):  
Periodic Potential ◽  
Direct Evidence ◽  
Interaction Strength ◽  
Fermi Gas ◽  
Model Systems ◽  
Strongly Correlated ◽  
Two Dimensional ◽  
Strong Correlations ◽  
Critical Temperatures ◽  
Reduced Dimensionality

Understanding how strongly correlated two-dimensional (2D) systems can give rise to unconventional superconductivity with high critical temperatures is one of the major unsolved problems in condensed matter physics. Ultracold 2D Fermi gases have emerged as clean and controllable model systems to study the interplay of strong correlations and reduced dimensionality, but direct evidence of superfluidity in these systems has been missing. We demonstrate superfluidity in an ultracold 2D Fermi gas by moving a periodic potential through the system and observing no dissipation below a critical velocity vc. We measure vc as a function of interaction strength and find a maximum in the crossover regime between bosonic and fermionic superfluidity. Our measurements enable systematic studies of the influence of reduced dimensionality on fermionic superfluidity.

scholarly journals Block product density matrix embedding theory for strongly correlated spin systems

2017 ◽  
Vol 95 (19) ◽  
Author(s):  
Klaas Gunst ◽  
Sebastian Wouters ◽  
Stijn De Baerdemacker ◽  
Dimitri Van Neck
Keyword(s):  
Density Matrix ◽  
Spin Systems ◽  
Strongly Correlated ◽  
Product Density ◽  
Embedding Theory ◽  
Matrix Embedding ◽  
Block Product

scholarly journals Strongly correlated flat-band systems: The route from Heisenberg spins to Hubbard electrons

2015 ◽  
Vol 29 (12) ◽  
pp. 1530007 ◽  
Author(s):  
Oleg Derzhko ◽  
Johannes Richter ◽  
Mykola Maksymenko
Keyword(s):  
Low Temperature ◽  
Ground State ◽  
Hard Core ◽  
Spin Systems ◽  
Square Lattice ◽  
Flat Band ◽  
Particle Spectrum ◽  
Strongly Correlated ◽  
Many Body ◽  
Hubbard Models

On a large class of lattices (such as the sawtooth chain, the kagome and the pyrochlore lattices), the quantum Heisenberg and the repulsive Hubbard models may host a completely dispersionless (flat) energy band in the single-particle spectrum. The flat-band states can be viewed as completely localized within a finite volume (trap) of the lattice and allow for construction of many-particle states, roughly speaking, by occupying the traps with particles. If the flat-band happens to be the lowest-energy one, the manifold of such many-body states will often determine the ground-state and low-temperature physics of the models at hand even in the presence of strong interactions. The localized nature of these many-body states makes possible the mapping of this subset of eigenstates onto a corresponding classical hard-core system. As a result, the ground-state and low-temperature properties of the strongly correlated flat-band systems can be analyzed in detail using concepts and tools of classical statistical mechanics (e.g., classical lattice-gas approach or percolation approach), in contrast to more challenging quantum many-body techniques usually necessary to examine strongly correlated quantum systems. In this review, we recapitulate the basic features of the flat-band spin systems and briefly summarize earlier studies in the field. The main emphasis is made on recent developments which include results for both spin and electron flat-band models. In particular, for flat-band spin systems, we highlight field-driven phase transitions for frustrated quantum Heisenberg antiferromagnets at low temperatures, chiral flat-band states, as well as the effect of a slight dispersion of a previously strictly flat-band due to nonideal lattice geometry. For electronic systems, we discuss the universal low-temperature behavior of several flat-band Hubbard models, the emergence of ground-state ferromagnetism in the square-lattice Tasaki–Hubbard model and the related Pauli-correlated percolation problem, as well as the dispersion-driven ground-state ferromagnetism in flat-band Hubbard systems. Closely related studies and possible experimental realizations of the flat-band physics are also described briefly.

Spin systems in strongly correlated random fields

1995 ◽  
Vol 140-144 ◽  
pp. 265-266
Author(s):  
L.L. Gonçalves
Keyword(s):  
Random Fields ◽  
Spin Systems ◽  
Strongly Correlated

MARGINAL FERMI LIQUID IN STRONGLY CORRELATED SPIN SYSTEMS

1994 ◽  
Vol 08 (14n15) ◽  
pp. 859-869
Author(s):  
A. P. PROTOGENOV ◽  
D. A. RYNDYK
Keyword(s):  
Excitation Spectrum ◽  
Fermi Liquid ◽  
Degrees Of Freedom ◽  
Chemical Potential ◽  
Collective Excitation ◽  
Spin Systems ◽  
Strongly Correlated ◽  
Band Center ◽  
Marginal Fermi Liquid ◽  
Self Consistent

We consider the consequences of the separation of spin and charge degrees of freedom in 2 + 1 D strongly correlated spin systems. Self-consistent spin and charge motions induced by doping in sites of ground and dual lattices form such a spectrum of quasiparticles which together with the dispersionless character of the collective excitation spectrum and the chemical potential pinning in the band center yield the necessary behavior to support the theory of marginal Fermi liquid formulated by C. M. Varma et al. (Phys. Rev. Lett.63, 1996 (1989)).

Anyon superconductivity in strongly-correlated spin systems

1992 ◽  
Vol 35 (7) ◽  
pp. 535-571 ◽  
Author(s):  
Aleksandr P Protogenov
Keyword(s):  
Spin Systems ◽  
Strongly Correlated
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