Larkin-Ovchinnikov-Fulde-Ferrell Phase Research Articles

Toward electrodynamics of unconventional phases of dilute nuclear matter

The phase diagram of isospin-asymmetrical nuclear matter may feature a number of unconventional phases, which include the translationally and rotationally symmetric, but isospin-asymmetrical BCS condensate, the current-carrying Larkin-Ovchinnikov-Fulde-Ferrell (LOFF) phase, and the heterogeneous phase-separated phase. Because the Cooper pairs of the condensate carry a single unit of charge, these phases are charged superconductors and respond to electromagnetic gauge fields by either forming domains (type-I superconductivity) or quantum vortices (type-II superconductivity). We evaluate the Ginzburg-Landau (GL) parameter across the phase diagram and find that the unconventional phases of isospin-asymmetrical nuclear matter are good type-II superconductors and should form Abrikosov vortices with twice the quantum of magnetic flux. We also find that the LOFF phase at the boundary of the transition to the type-I state, with the GL parameter being close to the critical value .

Solid-state calculation of crystalline color superconductivity

It is generally believed that the inhomogeneous Larkin-Ovchinnikov-Fulde-Ferrell (LOFF) phase appears in a color superconductor when the pairing between different quark flavors is under the circumstances of mismatched Fermi surfaces. However, the real crystal structure of the LOFF phase is still unclear because an exact treatment of 3D crystal structures is rather difficult. In this work we present a solid-state-like calculation of the ground-state energy of the body-centered cubic (BCC) structure for two-flavor pairing by diagonalizing the Hamiltonian matrix in the Bloch space without assuming a small amplitude of the order parameter. We develop a computational scheme to overcome the difficulties in diagonalizing huge matrices. Our results show that the BCC structure is energetically more favorable than the 1D modulation in a narrow window around the conventional LOFF-normal phase transition point, which indicates the significance of the higher-order terms in the Ginzburg-Landau approach.

Larkin-Ovchinnikov-Fulde-Ferrell phase in the superconductor(TMTSF)2ClO4: Theory versus experiment

We consider a formation of the Larkin-Ovchinnikov-Fulde-Ferrell (LOFF) phase in a quasi-one-dimensional (Q1D) conductor in a magnetic field, parallel to its conducting chains, where we take into account both the paramagnetic spin splitting and orbital destructive effects against superconductivity. We show that, due to a relative weakness of the orbital effects in a Q1D case, the LOFF phase appears in ${(\text{TMTSF})}_{2}{\text{ClO}}_{4}$ superconductor for real values of its Q1D band parameters. We compare our theoretical calculations with the recent experimental data by Y. Maeno's group [S. Yonezawa et al., Phys. Rev. Lett. 100, 117002 (2008)] and show that there is a good qualitative and quantitative agreement between the theory and experimental data.

Column density and temperature effects on narrow resonance structures in atomic photoionization and photoabsorption

We consider a formation of the Larkin-Ovchinnikov-Fulde-Ferrell (LOFF) phase in a quasi-one-dimensional (Q1D) conductor in a magnetic field, parallel to its conducting chains, where we take into account both the paramagnetic spin-splitting and orbital destructive effects against superconductivity. We show that, due to a relative weakness of the orbital effects in a Q1D case, the LOFF phase appears in (TMTSF)$_2$ClO$_4$ superconductor for real values of its Q1D band parameters. We compare our theoretical calculations with the recent experimental data by Y. Maeno's group [S. Yonezawa et al., Phys. Rev. Lett. \textbf{100}, 117002 (2008)] and show that there is a good qualitative and quantitative agreement between the theory and experimental data.

The three-flavor LOFF phase of QCD

We explore the Larkin-Ovchinnikov-Fulde-Ferrell (LOFF) phase of QCD with three flavors, using the Ginzburg-Landau expansion of the free energy, and the NJL pointlike four-fermion interaction, with the quantum numbers of single-gluon exchange.

Complete Gluonic Phase in Two-Flavour Colour Superconductivity

We study a typical complete gluonic phase (LGP) in two-flavour colour superconductivity (2SC) by calculating the essential cubic and quartic interfering term between the gluonic condensates «Az(8)» and «Az(6)» with a gauged NJL model. It is proven that the coefficients of the cubic interfering term and the vacuum contributions of the cubic and quartic interfering term are all equal to zeroes. The coefficients of the quartic interfering term and the «Az(6)»'s quartic self-interaction term at stationary points of Larkin-Ovchinnikov-Fulde-Ferrell (LOFF) phase are calculated. Comparisons among the effective potentials of LGP, g2SC and LOFF phase indicate that LGP could be the genuine ground state of 2SC for some reasonable parameters.

Larkin-Ovchinnikov-Fulde-Ferrell state in two-color quark matter

We explore the phase structure of two-color and two-flavor QCD in the space of the quark chemical potential ${\ensuremath{\mu}}_{\mathrm{q}}$ and the isospin chemical potential ${\ensuremath{\mu}}_{\mathrm{I}}$. Using a mean-field model we calculate the chiral and diquark condensates, $\ensuremath{\sigma}$ and $\ensuremath{\Delta}$, self-consistently. In weak coupling and in the chiral limit, we confirm the interval of the isospin chemical potential, $0.71{\ensuremath{\Delta}}_{0}<{\ensuremath{\mu}}_{\mathrm{I}}<0.75{\ensuremath{\Delta}}_{0}$, in which a single plane-wave Larkin-Ovchinnikov-Fulde-Ferrell (LOFF) phase is favored over isotropic superfluidity and normal quark matter. The LOFF window becomes slightly wider at high density. For stronger coupling with nonzero quark mass, which is relevant to currently available numerical simulations in lattice two-color QCD, the single plane-wave LOFF phase appears only at sufficiently high density. The prediction obtained for the LOFF region could be tested with lattice since we can prove that the present system is free from the fermion sign problem. We draw the energy landscape on which local minima corresponding to the isotropic superfluid phase and the LOFF phase and a local maximum corresponding to the gapless phase are manifest. Our results clearly illustrate the path from the unstable gapless phase down to the LOFF phase.

Influence of finite quark chemical potentials on the three flavor LOFF phase of QCD

Abstract We study, in the Ginzburg–Landau approximation, the Larkin–Ovchinnikov–Fulde–Ferrell (LOFF) phase of QCD with three flavors and one plane wave, including terms of order O ( 1 / μ ) . We show that the LOFF window is slightly enlarged, and actually splits into two different regions, one characterized by u – s and d – u pairings and the other with d – u pairs only.

Ginzburg–Landau approach to the three flavor LOFF phase of QCD

We explore, using a Ginzburg–Landau expansion of the free energy, the Larkin–Ovchinnikov–Fulde–Ferrell (LOFF) phase of QCD with three flavors, using the NJL four-fermion coupling to mimic gluon interactions. We find that, below the point where the QCD homogeneous superconductive phases should give way to the normal phase, Cooper condensation of the pairs u–s and d–u is possible, but in the form of the inhomogeneous LOFF pairing.

Inhomogeneous stripe phase revisited for surface superconductivity.

We consider 2D surface superconductivity in high magnetic fields parallel to the surface. We demonstrate that the spin-orbit interaction at the surface changes the properties of the inhomogeneous superconducting Larkin-Ovchinnikov-Fulde-Ferrell (LOFF) state that develops above fields given by the paramagnetic criterion. Strong spin-orbit interaction significantly broadens the range of existence of the LOFF phase, which takes the form of periodic superconducting stripes running along the field direction on the surface, leading to the anisotropy of its properties. Our results provide a tool for studying surface superconductivity as a function of doping.