scholarly journals Generalized susceptibilities and Landau parameters for anisotropic Fermi liquids

2015 ◽  
Vol 29 (16) ◽  
pp. 1550102
Author(s):  
P. Rodríguez-Ponte ◽  
D. Cabra ◽  
N. Grandi
Keyword(s):  
Fermi Surface ◽  
Linear Response ◽  
Order Parameter ◽  
Rotational Invariance ◽  
Fermi Liquids ◽  
Quartic Interaction ◽  
Definition Of

We study Fermi liquids (FLs) with a Fermi surface that lacks continuous rotational invariance and in the presence of an arbitrary quartic interaction. We obtain the expressions of the generalized static susceptibilities that measure the linear response of a generic order parameter to a perturbation of the Hamiltonian. We apply our formulae to the spin and charge susceptibilities. Based on the resulting expressions, we make a proposal for the definition of the Landau parameters in nonisotropic FL.

scholarly journals What Can Positrons Contribute to High-Tc Superconductivity?

1993 ◽  
Vol 48 (1-2) ◽  
pp. 390-397 ◽  
Author(s):  
M. Peter ◽  
T. Jarlborg ◽  
A. A. Manuel ◽  
B. Barbiellini
Keyword(s):  
Fermi Surface ◽  
Anderson Localization ◽  
Charge Density Waves ◽  
Actual Situation ◽  
Many Body ◽  
Fermi Surfaces ◽  
High Tc ◽  
Superconducting Oxides ◽  
Lifetime Studies ◽  
Definition Of

Abstract The positron annihilation technique has made well-known contributions to the study of Fermi surfaces in "classical" superconductors, including A15 phases where the definition of the Fermi surface has been questioned on the grounds of Anderson localization. In the case of the superconducting oxides, even more far out models were proposed, which made the clear imaging of the Fermi surface by positrons desirable. The difficulties due to the predicted weakness of the signal, and the large possibility for trapping have now been surmounted and the Fermi surface has been seen; what more can we learn from positrons?After presenting the actual situation with experiment, we will comment on enhancement and correlation and their effect on ACAR and lifetime studies. Then we explain the picture of Jarlborg and Singh of enhancement, with its recent tests for many substances. We conclude by asking the question of sensitivity of positrons to many-body effects. Ferromagnetism, antiferromagnetism, possibly charge density waves have been seen -superconductors, heavy fermions and spinons-holons would pose a problem.Stephan Berko (1924-1991) was interested in these problems and knew that better machines and better detectors would open new possibilities.

Definition of a Transcendental Order Parameter for Reconstructive Phase Transitions

1988 ◽  
Vol 60 (19) ◽  
pp. 1958-1961 ◽  
Author(s):  
V. P. Dmitriev ◽  
S. B. Rochal ◽  
Yu. M. Gufan ◽  
P. Toledano
Keyword(s):  
Phase Transitions ◽  
Order Parameter ◽  
Definition Of

On the linear response of Bardeen–Cooper–Schrieffer superconductors I. clean superconductors

1986 ◽  
Vol 64 (10) ◽  
pp. 1396-1400
Author(s):  
Robert Cleary
Keyword(s):  
Function Approximation ◽  
Linear Response ◽  
Point Charge ◽  
Order Parameter ◽  
Pair Potential ◽  
Delta Function ◽  
Magnetic Vector Potential ◽  
Point Dipole ◽  
Magnetic Vector ◽  
Bare Potential

We calculate the linear response of a Bardeen–Cooper–Schrieffer superconductor to transverse and longitudinal electromagnetic radiation. Oscillations in the pair potential are also investigated. The order parameter and electric field of a point charge imbedded in a superconductor are also calculated. We assume a reasonable bare potential for the point charge. Finally, the linear response to the order parameter and magnetic vector potential is calculated for a reasonable model of a magnetic point dipole, again employing a more accurate model for the spin impurity than the usual delta-function approximation.

Invariance Considerations in Large Strain Elasto-Plasticity

1986 ◽  
Vol 53 (1) ◽  
pp. 55-60 ◽  
Author(s):  
P. A. Dashner
Keyword(s):  
Large Strain ◽  
Deformation Gradient ◽  
Rotational Invariance ◽  
Rotational Component ◽  
Microstructural Characteristics ◽  
Ongoing Debate ◽  
Anisotropic Crystal ◽  
Elasto Plasticity ◽  
Definition Of ◽  
Material Frame

This paper addresses a number of issues in the ongoing debate over the relevance and/or appropriateness of the rotational invariance requirement which is generally associated with the intermediate unstressed configuration. In particular, it is argued that the principle of material frame invariance has been “misapplied” by the proponents of full rotational invariance. Insistence on a strictly “kinematic” interpretation of the deformation gradient (F = FeFp) constituents Fe and Fp justifies elimination of the plastic rotational component Rp(Fp = RpUp) based on the principle of determinism for stress — not invariance of frame. However, simple physical considerations, including a physical example involving a “structurally anisotropic” crystal, suggest that a more intricate definition of the gradient constituents is required in order to adequately account for microstructural characteristics. These considerations suggest alternative definitions for the gradient constituents Fe and Fp with associated constitutive invariance requirements.

STRANGE METALS AND HOLOGRAPHIC ENTANGLEMENT ENTROPY

2013 ◽  
Vol 28 (03n04) ◽  
pp. 1340004 ◽  
Author(s):  
TADASHI TAKAYANAGI
Keyword(s):  
Fermi Surface ◽  
High Energy Phys ◽  
Classical Limit ◽  
Entanglement Entropy ◽  
High Energy ◽  
Fermi Liquids ◽  
Surface Physics ◽  
Holographic Entanglement Entropy ◽  
Gravity Duals

In this paper, we will explain an application of holographic entanglement entropy to Fermi surface physics. These holographic arguments show that Landau–Fermi liquids do not have any gravity duals in the purely classical limit [N. Ogawa, T. Takayanagi and T. Ugajin, J. High Energy Phys.125, 1 (2012), arXiv:1111.1023 [hep-th]].

scholarly journals DYNAMICS OF T=0 BCS CONDENSATES

1995 ◽  
Vol 09 (11) ◽  
pp. 1359-1373 ◽  
Author(s):  
MICHAEL STONE
Keyword(s):  
Fermi Surface ◽  
Order Parameter ◽  
Schrodinger Equation ◽  
Linear Time ◽  
Time Dependent ◽  
Pitaevskii Equation ◽  
Long Wavelength ◽  
Non Linear ◽  
Bose Superfluid ◽  
Galilean Invariant

Fermi-surface bosonization is used to show that the long-wavelength, T=0, dynamics of a BCS superfluid or superconductor is described by a galilean invariant non-linear time-dependent Schrödinger equation. This equation is of same form as the Gross-Pitaevskii equation for a Bose superfluid, but the “wavefunction” is not the superfluid order parameter.

Neutron–antineutron oscillation and discrete symmetries

2018 ◽  
Vol 33 (31) ◽  
pp. 1844016 ◽  
Author(s):  
Zurab Berezhiani ◽  
Arkady Vainshtein
Keyword(s):  
Magnetic Field ◽  
External Magnetic Field ◽  
Text Classification ◽  
Discrete Symmetries ◽  
Rotational Invariance ◽  
Baryon Charge ◽  
Free Particles ◽  
Definition Of ◽  
Charge Formula

We analyze status of [Formula: see text], [Formula: see text] and [Formula: see text] discrete symmetries in application to neutron–antineutron transitions breaking conservation of baryon charge [Formula: see text] by two units. At the level of free particles, all these symmetries are preserved. This includes [Formula: see text] reflection in spite of the opposite internal parities usually ascribed to neutron and antineutron. Explanation, which goes back to the 1937 papers by Majorana and Racah, is based on a definition of parity satisfying [Formula: see text], instead of [Formula: see text], and ascribing [Formula: see text] to both, neutron and antineutron. We apply this to [Formula: see text], [Formula: see text] and [Formula: see text] classification of six-quark operators with [Formula: see text]. It allows to specify operators contributing to neutron–antineutron oscillations. Remaining operators contribute to other [Formula: see text] processes and, in particular, to nuclei instability. We also show that presence of external magnetic field does not induce any new operator mixing the neutron and antineutron provided that rotational invariance is not broken.

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