Ground-state instability in systems of strongly interacting fermions

Artamonov, S.A.; Shaginyan, V. R.; Pogorelov, Yu. G.

doi:10.1134/1.567952

Cited by 42 publications

(39 citation statements)

References 8 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…Fig. 5 demonstrates the behavior of the spectra within the same model (32), but at α = 4.2. These results inform us that at α = 1.5 the spectrum ǫ(p) assumes negative values only at T < 0.05ǫ 0 F , and only over a small range at small p, while at α = 4.2 the function ǫ(p) becomes positive independently of both momentum p and temperature T .…”

mentioning

confidence: 99%

“…The bandwidth W = |ǫ(p = 0)| is seen to shrink dramatically as the interaction strength approaches a critical value, at which the stability of the conventional Landau state with n(p) = θ(p F − p) is lost and the Fermi surface becomes multi-connected. 31,32 In the vicinity of the critical point, the single root p F (T ) of Eq. (31) at which the spectrum ǫ(p, T ) changes sign is found to approach zero rapidly as the temperature T is raised.…”

mentioning

confidence: 99%

See 1 more Smart Citation

Conventional BCS, unconventional BCS, and non-BCS hidden dineutron phases in neutron matter

et al. 2014

Self Cite

View full text Add to dashboard Cite

The nature of pairing correlations in neutron matter is re-examined. Working within the conventional approximation in which the nn pairing interaction is provided by a realistic bare nn potential fitted to scattering data, it is demonstrated that the standard BCS theory fails in regions of neutron number density where the pairing constant λ, depending crucially on density, has a non-BCS negative sign. We are led to propose a non-BCS scenario for pairing phenomena in neutron matter that involves the formation of a hidden dineutron state. In low-density neutron matter where the pairing constant has the standard BCS sign, two phases organized by pairing correlations are possible and compete energetically: a conventional BCS phase and a dineutron phase. In dense neutron matter, where λ changes sign, only the dineutron phase survives and exists until the critical density for termination of pairing correlations is reached at approximately twice the neutron density in heavy atomic nuclei. PREAMBLEThis contribution is dedicated with deep respect and admiration to Spartak Timofeevich Belyaev on the occasion of his 90th birthday. Three generations of physicists across the globe have taken inspiration from his prodigious achievements in theoretical nuclear physics and quantum many-body theory, as well as his wise and visionary leadership in the development and sustenance of world-renowned scientific institutions. Recognized by awards of the 2004 Feenberg Memorial Medal and the 2012 Pomeranchuk Prize as one of the founding fathers of modern many-body theory based on field-theoretic methods, he introduced the concept of anomalous propagators 1 that runs through all of current theoretical physics and is central to a microscopic understanding of pairing phenomena in nuclear and condensed matter systems. The impact of the profound advances he made in the theory of nuclear superfluidity during his 1957-58 "wonder year" at the Bohr Institute and later in Novosibirsk, changed the course of nuclear theory, giving rise to the "standard nuclear paradigm" in which BCS pairing correlations assume pivotal roles. S. T. has taught us4 that "There is still a vast field of unsolved problems stimulating the progress of theoretical nuclear physics." Our contribution to this celebratory issue is offered very much in the same spirit, as we seek to establish that the study of pairing correlations remains a source of surprising and intriguing revelations about the microworld.

show abstract

mentioning

confidence: 99%

mentioning

confidence: 99%

Conventional BCS, unconventional BCS, and non-BCS hidden dineutron phases in neutron matter

et al. 2014

Self Cite

View full text Add to dashboard Cite

show abstract

“…We note that there are different kinds of instabilities of LFL connected with several perturbations of initial quasiparticle spectrum ε(p) and occupation numbers n(p), associated with strong enhancement of the effective mass and leading to the emergence of a multi-connected Fermi surface, see e.g. [8,[21][22][23]. Depending on the parameters and analytical properties of the Landau interaction, such instabilities lead to several possible types of restructuring of the initial LFL ground state.…”

mentioning

confidence: 99%

Heat transport in magnetic fields by quantum spin liquid in the organic insulators EtMe ₃ Sb[Pd(dmit) ₂ ] ₂ and κ -(BEDT - TTF) ₂ Cu ₂ (CN) ₃

Shaginyan¹,

Msezane²,

Попов³

et al. 2013

EPL

Self Cite

View full text Add to dashboard Cite

-Measurements of the low-temperature thermal conductivity collected on insulators with geometrical frustration produce important experimental facts shedding light on the nature of quantum spin liquid composed of spinons. We employ a model of strongly correlated quantum spin liquid located near the fermion condensation phase transition to analyze the exciting measurements of the low-temperature thermal conductivity in magnetic fields collected on the organic insulators EtMe3Sb[Pd(dmit)2]2 and κ − (BEDT − TTF)2Cu2(CN)3. Our analysis of the conductivity allows us to reveal a strong dependence of the effective mass of spinons on magnetic fields, to detect a scaling behavior of the conductivity, and to relate it to both the spin-lattice relaxation rate and the magnetoresistivity. Our calculations and observations are in a good agreement with experimental data.The organic insulators EtMe 3 Sb[Pd(dmit) 2 ] 2 and κ − (BEDT − TTF) 2 Cu 2 (CN) 3 have two-dimensional triangular lattices with the geometric frustration prohibiting the formation of spin ordering even at the lowest accessible temperatures T [1-5]. Therefore, these insulators offer unique insights into the physics of quantum spin liquids (QSL). Indeed, measurements of the heat capacity on the both insulators reveal a T -linear term indicating that the low-energy excitation spectrum from the ground state is gapless [1][2][3]. The excitation spectrum can be deduced from measurements of the heat conductivity κ(T ) in the low temperature regime. For example, at T → 0 a residual value in k/T signals that the excitation spectrum is gapless. The presence of the residual value is clearly resolved in EtMe 3 Sb[Pd(dmit) 2 ] 2 , while measurements of k/T on κ − (BEDT − TTF) 2 Cu 2 (CN) 3 suggests that the low-energy excitation spectrum can have a gap (a) Email: vrshag@thd.pnpi.spb.ru [4,5]. Taking into account the observed T -linear term of the heat capacity in κ − (BEDT − TTF) 2 Cu 2 (CN) 3 with the static spin susceptibility remaining finite down to the lowest measured temperatures [6], the presence of the spin excitation gap becomes questionable. Thermal conductivity probe elementary itinerant excitations and is totally insensitive to localized ones such as those responsible for Schottky contributions, which contaminates the heat capacity measurements at low temperatures [1][2][3][4][5]. The heat conductivity is formed primarily by both acoustic phonons and itinerant spinons, while the latter form QSL. Since the phonon contribution is insensitive to the applied magnetic field B, the elementary excitations of QSL can be further explored by the magnetic field dependence of k. Measurements under the application of magnetic field B of the heat conductivity κ on these insulators have exhibited a strong dependence of κ(B, T ) as a function of B at fixed T [4,5]. The obtained dependence at low temperatures rep-1

show abstract

“…We note that there are different kinds of instabilities of normal Fermi liquids connected with several perturbations of initial quasiparticle spectrum ε(p) and occupation numbers n(p), associated with the emergence of a multi-connected Fermi surface, see e.g. [5,[22][23][24]. Depending on the parameters and analytical properties of the Landau interaction, such instabilities lead to several possible types of restructuring of the initial Fermi liquid ground state.…”

Section: Phase Diagrams Of Strongly Correlated Fermi Systemsmentioning

confidence: 99%

Fermion condensate generates a new state of matter by making flat bands

2014

Self Cite

View full text Add to dashboard Cite

This short review paper devoted to 90th anniversary of S. T. Belyaev birthday. Belyaev's ideas associated with the condensate state in Bose interacting systems have stimulated intensive studies of the possible manifestation of such a condensation in Fermi systems. In many Fermi systems and compounds at zero temperature a phase transition happens that leads to a quite specific state called fermion condensation. As a signal of such a fermion condensation quantum phase transition (FCQPT) serves unlimited increase of the effective mass of quasiparticles that determines the excitation spectrum and creates flat bands. We show that the class of Fermi liquids with the fermion condensate forms a new state of matter. We discuss the phase diagrams and the physical properties of systems located near that phase transition. A common and essential feature of such systems is quasiparticles different from those suggested by L. D. Landau, by crucial dependence of their effective mass on temperature, external magnetic field, pressure etc. It is demonstrated that a huge amount of experimental data collected on different compounds suggests that they, starting from some temperature and down, form the new state of matter, and are governed by the fermion condensation. Our discussion shows that the theory of fermion condensation develops completely good description of the NFL behavior of strongly correlated Fermi systems. Moreover, the fermion condensation can be considered as the universal reason for the NFL behavior observed in various HF metals, liquids, compounds with quantum spin liquids, and quasicrystals. We show that these systems exhibit universal scaling behavior of their thermodynamic properties. Therefore, the quantum critical physics of different strongly correlated compounds is universal, and emerges regardless of the underlying microscopic details of the compounds. This uniform behavior, governed by the universal quantum critical physics, allows us to view it as the main characteristic of the new state of matter.

show abstract

Ground-state instability in systems of strongly interacting fermions

Cited by 42 publications

References 8 publications

Conventional BCS, unconventional BCS, and non-BCS hidden dineutron phases in neutron matter

Conventional BCS, unconventional BCS, and non-BCS hidden dineutron phases in neutron matter

Heat transport in magnetic fields by quantum spin liquid in the organic insulators EtMe ₃ Sb[Pd(dmit) ₂ ] ₂ and κ -(BEDT - TTF) ₂ Cu ₂ (CN) ₃

Fermion condensate generates a new state of matter by making flat bands

Contact Info

Product

Resources

About

Ground-state instability in systems of strongly interacting fermions

Cited by 42 publications

References 8 publications

Conventional BCS, unconventional BCS, and non-BCS hidden dineutron phases in neutron matter

Conventional BCS, unconventional BCS, and non-BCS hidden dineutron phases in neutron matter

Heat transport in magnetic fields by quantum spin liquid in the organic insulators EtMe 3 Sb[Pd(dmit) 2 ] 2 and κ -(BEDT - TTF) 2 Cu 2 (CN) 3

Fermion condensate generates a new state of matter by making flat bands

Contact Info

Product

Resources

About

Heat transport in magnetic fields by quantum spin liquid in the organic insulators EtMe ₃ Sb[Pd(dmit) ₂ ] ₂ and κ -(BEDT - TTF) ₂ Cu ₂ (CN) ₃