LOCAL MINIMIZERS FOR THE GINZBURG–LANDAU ENERGY NEAR CRITICAL MAGNETIC FIELD: PART I

1999 ◽  
Vol 01 (02) ◽  
pp. 213-254 ◽  
Author(s):  
SYLVIA SERFATY
Keyword(s):  
Magnetic Field ◽  
Phase Transition ◽  
Critical Value ◽  
Critical Magnetic Field ◽  
Two Dimensional ◽  
Local Minimizers ◽  
Large Parameter ◽  
Ginzburg Landau

We find local minimizers of the two-dimensional Ginzburg–Landau functionals depending on a large parameter κ, which describe the behavior of a superconductor in a prescribed exterior magnetic field hex. We prove an estimate on the critical value Hc1 of hex(κ), corresponding to the first phase-transition in which vortices appear in the superconductor; and we locate these vortices.

LOCAL MINIMIZERS FOR THE GINZBURG–LANDAU ENERGY NEAR CRITICAL MAGNETIC FIELD: PART II

1999 ◽  
Vol 01 (03) ◽  
pp. 295-333 ◽  
Author(s):  
SYLVIA SERFATY
Keyword(s):  
Magnetic Field ◽  
Critical Field ◽  
Critical Magnetic Field ◽  
Asymptotic Limit ◽  
Local Minimizers ◽  
Ginzburg Landau ◽  
London Equation ◽  
Stable Solutions

As in Part I, we study local minimizers of the Ginzburg–Landau energy (depending on κ → +∞) for superconductors in a prescribed magnetic field hex. For disc domains, we find and describe stable solutions of the associated equations and show how vortices appear as hex is raised from the first critical field Hc1. We also study the asymptotic limit κ→∞ for hex=Hc1 and prove that the limiting magnetic field in the superconductor satisfies the London equation.

scholarly journals Theoretical Study of Upper Critical Magnetic Field (HC2) in Multiband Iron Based Superconductors

2016 ◽  
Vol 2016 ◽  
pp. 1-10 ◽  
Author(s):  
Tsadik Kidanemariam ◽  
Gebregziabher Kahsay
Keyword(s):  
Magnetic Field ◽  
Phase Diagrams ◽  
Penetration Depth ◽  
Coherence Length ◽  
Symmetry Axis ◽  
Critical Magnetic Field ◽  
Ginzburg Landau ◽  
Iron Based Superconductors ◽  
Upper Critical Magnetic Field ◽  
Iron Based

This research work focuses on the theoretical investigation of the upper critical magnetic field,HC2; Ginzburg-Landau coherence length,ξGL(T); and Ginzburg-Landau penetration depth,λGL(T), for the two-band iron based superconductorsBaFe2(As1-xPx)2,NdO1-xFxFeAs, and LiFeAs. By employing the phenomenological Ginzburg-Landau (GL) equation for the two-band superconductorsBaFe2(As1-xPx)2,NdO1-xFxFeAs, and LiFeAs, we obtained expressions for the upper critical magnetic field,HC2; GL coherence length,ξGL; and GL penetration depth,λGL, as a function of temperature and the angular dependency of upper critical magnetic field. By using the experimental values in the obtained expressions, phase diagrams of the upper critical magnetic field parallel,HC2∥c, and perpendicular,HC2⊥c, to the symmetry axis (c-direction) versus temperature are plotted. We also plotted the phase diagrams of the upper critical magnetic field,HC2versus the angleθ. Similarly, the phase diagrams of the GL coherence length,ξGL, and GL penetration depth,λGL, parallel and perpendicular to the symmetry axis versus temperature are drawn for the superconductors mentioned above. Our findings are in agreement with experimental observations.

scholarly journals Experimental Observation of Temperature-Driven Topological Phase Transition in HgTe/CdHgTe Quantum Wells

2019 ◽  
Author(s):  
Maksim Zholudev ◽  
Aleksandr Kadykov ◽  
Mikhail Fadeev ◽  
Michal Marcinkiewicz ◽  
Sandra Ruffenach ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Phase Transition ◽  
Quantum Wells ◽  
Topological Insulator ◽  
Critical Magnetic Field ◽  
Topological Phase ◽  
Temperature Dependent ◽  
Transition Parameter ◽  
Topological Phase Transition ◽  
Band Insulator

We report on comparison between temperature-dependent magneto¬absorption and magnetotransport spectroscopy of HgTe/CdHgTe quantum wells in terms of detection of phase transition between topological insulator and band insulator states. Our results demonstrate that temperature-dependent magnetospectroscopy is a powerful tool to discriminate trivial and topological insulator phases, yet magnetotransport method is shown to have advantages for clear manifestation of the phase transition with accurate quantitative values of transition parameter (i.e. critical magnetic field Bc).

scholarly journals Restoration of superconductivity in high magnetic fields in UTe2

2020 ◽  
Vol 34 (32) ◽  
pp. 2030007
Author(s):  
Andrei G. Lebed
Keyword(s):  
Magnetic Field ◽  
Magnetic Fields ◽  
Superconducting State ◽  
Critical Magnetic Field ◽  
High Magnetic Fields ◽  
Two Dimensional ◽  
Upper Critical Magnetic Field ◽  
Reentrant Superconductivity ◽  
Theoretical Results ◽  
General Method

It was theoretically predicted more than 20 years ago [A. G. Lebed and K. Yamaji, Phys. Rev. Lett. 80, 2697 (1998)], that a triplet quasi-two-dimensional (Q2D) superconductor could restore its superconducting state in parallel magnetic fields, which are higher than its upper critical magnetic field, [Formula: see text]. It is very likely that, recently, such phenomenon has been experimentally discovered in the Q2D superconductor UTe2 by Nicholas Butch, Sheng Ran, and their colleagues and has been confirmed by Japanese–French team. We review our previous theoretical results using such a general method that it describes the reentrant superconductivity in the abovementioned compound and will hopefully describes the similar phenomena, which can be discovered in other Q2D superconductors.

Phase transition in the random triangle model

1999 ◽  
Vol 36 (04) ◽  
pp. 1101-1115 ◽  
Author(s):  
Olle Häggström ◽  
Johan Jonasson
Keyword(s):  
Phase Transition ◽  
Social Networks ◽  
Ising Model ◽  
Hexagonal Lattice ◽  
Graph Model ◽  
Finite Graph ◽  
Critical Value ◽  
Two Dimensional ◽  
Random Graph Model ◽  
Image Position

The random triangle model was recently introduced as a random graph model that captures the property of transitivity that is often found in social networks, i.e. the property that given that two vertices are second neighbors, they are more likely to be neighbors. For parameters p ∊ [0,1] and q ≥ 1, and a finite graph G = (V, E), it assigns to elements η of {0,1} E probabilities which are proportional to where t(η) is the number of triangles in the open subgraph. In this paper the behavior of the random triangle model on the two-dimensional triangular lattice is studied. By mapping the system onto an Ising model with external field on the hexagonal lattice, it is shown that phase transition occurs if and only if p = (q−1)−2/3 and q > q c for a critical value q c which turns out to equal It is furthermore demonstrated that phase transition cannot occur unless p = p c (q), the critical value for percolation of open edges for given q. This implies that for q ≥ q c , p c (q) = (q−1)−2/3.

Local Minimizers of the Ginzburg-Landau Energy with Magnetic Field in Three Dimensions

2004 ◽  
Vol 249 (3) ◽  
pp. 549-577 ◽  
Author(s):  
Robert Jerrard ◽  
Alberto Montero ◽  
Peter Sternberg
Keyword(s):  
Magnetic Field ◽  
Three Dimensions ◽  
Local Minimizers ◽  
Ginzburg Landau
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