QCD in magnetic field, Landau levels and double-life of unbroken center-symmetry

Anber, Mohamed M.; Ünsal, Mithat

doi:10.1007/jhep12(2014)107

Cited by 7 publications

(6 citation statements)

References 96 publications

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“…Remember that the vortex-anti-vortex interaction energy is solely due to the unbroken U(1) A 7. A similar phenomenon where the magnetic field can suppress phase transition was also noticed in Ref [12]…”

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confidence: 73%

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Model for superconductivity at any temperature

et al. 2016

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We construct a 2+1 dimensional model that sustains superconductivity at all temperatures. This is achieved by introducing a Chern Simons mixing term between two Abelian gauge fields A and Z. The superfluid is described by a complex scalar charged under Z, whereas a sufficiently strong magnetic field of A forces the superconducting condensate to form at all temperatures. In fact, at finite temperature, the theory exhibits Berezinsky-Kosterlitz-Thouless phase transition due to proliferation of topological vortices admitted by our construction. However, the critical temperature is proportional to the magnetic field of A, and thus, the phase transition can be postponed to high temperatures by increasing the strength of the magnetic field. This model can be a step towards realizing the long sought room temperature superconductivity.PACS numbers: 11.15. Wx, 11.15.Yc, Introduction.-Superconductivity is one of the most fascinating phenomena in nature that has attracted the attention of both theorists and experimentalists since its discovery in 1911. Superconductors exhibit the so called Meissner effect [1], namely, the expulsion of external magnetic field lines. It was London brothers who first gave a phenomenological understanding of the Meissner effect [2]. A breakthrough idea was developed by Landau and Ginzburg who provided a framework to describe superconductivity using mean field theory approach [3]. In their macroscopic theory of superconductivity, the superfluid is described by a complex scalar field whose expectation value is the order parameter that distinguishes between the superconducting and normal phases. The microscopic structure of the condensate was explained by Bardeen, Cooper and Schrieffer [4] as the pairing of electrons via phonon interactions. Yet another breakthrough came during the 1980s, when it was discovered that certain materials become superconductors at relatively high temperatures, T ∼ 90 − 130 K. Since then, it has remained a true challenge to achieve superconductivity at higher temperatures, ultimately all the way up to room temperature. In fact, constructing a model that has a superconducting phase at high temperatures can be a step towards realizing this quest.

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confidence: 73%

“…7 A similar phenomenon where the magnetic field can suppress phase transition was also noticed in Ref. [12].…”

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confidence: 64%

Model for superconductivity at any temperature

et al. 2016

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“…This is expected to be accurate, given the smallness of the coupling Hµ ∝ g 4μ ≪ 1. The Hubbard-Stratonovich transformation applied to (51) with an auxiliary complex field ∆(x) yields…”

Section: Fermionic Effective Theorymentioning

confidence: 99%

Phases of circle-compactified QCD with adjoint fermions at finite density

Kanazawa¹,

Ünsal

Yamamoto

2017

Phys. Rev. D

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We study chemical-potential dependence of confinement and mass gap in QCD with adjoint fermions in spacetime with one spatial compact direction. By calculating the one-loop effective potential for the Wilson line in the presence of chemical potential, we show that a center-symmetric phase and a center-broken phase alternate when the chemical potential in unit of the compactification scale is increased. In the center-symmetric phase we use semiclassical methods to show that photons in the magnetic bion plasma acquire a mass gap that grows with the chemical potential as a result of anisotropic interactions between monopole-instantons. For the neutral fermionic sector which remains gapless perturbatively, there are two possibilities at non-perturbative level. Either to remain gapless (unbroken global symmetry), or to undergo a novel superfluid transition through a fourfermion interaction (broken global symmetry). If the latter is the case, this leads to an energy gap of quarks proportional to a new nonperturbative scale L −1 exp[−1 (g 4 µL)], where L denotes the circumference of S 1 , the low-energy is described as a Nambu-Goldstone mode associated with the baryon number, and there exists a new type of BEC-BCS crossover of the diquark pairing as a function of the compactification scale at small chemical potential.

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“…Thus, interestingly, QCD seems to undergo a characteristic change in its magnetic profile at finite temperature, despite the absence of a genuine phase transition. On the theoretical side, the magnetization and magnetic susceptibility of QCD at zero density have been studied in, e.g., perturbative QCD [47], the Hadron Resonance Gas model [48], holographic QCD [49], a transport model [50], a potential model [51], a non-interacting quark gas with the Polyakov loop [52], spatially compactified QCD [53] and the SU(3) linear sigma model with the Polyakov loop [54].…”

Section: Introductionmentioning

confidence: 99%

Magnetic susceptibility of a strongly interacting thermal medium with 2 + 1 quark flavors

Kamikado

Kanazawa

2015

J. High Energ. Phys.

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Thermodynamics of the three-flavor quark-meson model with U A (1) anomaly is studied in the presence of external magnetic fields. The nonperturbative functional renormalization group is employed in order to incorporate quantum and thermal fluctuations beyond the mean-field approximation. We calculate the magnetic susceptibility with proper renormalization and find that the system is diamagnetic in the hadron phase and paramagnetic in the hot plasma phase. The obtained values of the magnetic susceptibility are in reasonable agreement with the data from first-principle lattice QCD. Comparison with the mean-field approximation, the Hadron Resonance Gas model and a free gas with temperature-dependent masses is also made.

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QCD in magnetic field, Landau levels and double-life of unbroken center-symmetry

Cited by 7 publications

References 96 publications

Model for superconductivity at any temperature

Model for superconductivity at any temperature

Phases of circle-compactified QCD with adjoint fermions at finite density

Magnetic susceptibility of a strongly interacting thermal medium with 2 + 1 quark flavors

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