scholarly journals Extremely high upper critical field in BiCh2-based (Ch: S and Se) layered superconductor LaO0.5F0.5BiS2−xSex (x = 0.22 and 0.69)

2022 ◽  
Vol 12 (1) ◽  
Author(s):  
Kazuhisa Hoshi ◽  
Ryosuke Kurihara ◽  
Yosuke Goto ◽  
Masashi Tokunaga ◽  
Yoshikazu Mizuguchi
Keyword(s):  
Symmetry Breaking ◽  
Critical Field ◽  
Upper Critical Field ◽  
Layered Superconductor ◽  
Inversion Symmetry ◽  
Critical Fields ◽  
Local Inversion ◽  
Upper Critical Fields ◽  
Spin Polarisation ◽  
Inversion Asymmetry

AbstractCentrosymmetric compounds with local inversion symmetry breaking have tremendously interesting and intriguing physical properties. In this study, we focus on a BiCh2-based (Ch: S, Se) layered superconductor, as a system with local inversion asymmetry, because spin polarisation based on the Rashba–Dresselhaus-type spin–orbit coupling has been observed in centrosymmetric BiCh2-based LaOBiS2 systems, while the BiCh2 layer lacks local inversion symmetry. Herein, we report the existence of extremely high in-plane upper critical fields in the BiCh2-based system LaO0.5F0.5BiS2−xSex (x = 0.22 and 0.69). The superconducting states are not completely suppressed by the applied magnetic fields with strengths up to 55 T. Thus, we consider that the in-plane upper critical field is enhanced by the local inversion symmetry breaking and its layered structure. Our study will open a new pathway for the discovery of superconductors that exhibit a high upper critical field by focusing on the local inversion symmetry breaking.

UPPER CRITICAL FIELD OF HIGH Tc SUPERCONDUCTING OXIDES

1987 ◽  
Vol 01 (02) ◽  
pp. 451-453
Author(s):  
Changgeng CUI ◽  
Shuquan GUO ◽  
Shanlin LI ◽  
Lie CHEN ◽  
Cheng DONG ◽  
...  
Keyword(s):  
Least Squares ◽  
Critical Field ◽  
High Field ◽  
Upper Critical Field ◽  
Critical Fields ◽  
High Tc ◽  
Dirty Limit ◽  
Straight Line ◽  
Upper Critical Fields ◽  
Superconducting Oxides

Upper critical fields Bc2(T) near Tc have been measured for the samples of Ba2YCu3Ox and Ba2GdCu3Ox. The upper critical field slope (dBc2dT)Tc and the upper critical field Bc2(O) have been calculated by using the least squares filling of straight line and using WHH expression in dirty limit respectively. The results show that Bc2(O) can be reach 114T and 127T for the samples of Ba2YCu3Ox and Ba2GdCu3Ox respectively. It is observed that there is a upwards curvature near Tc in the curves of B(T) vs.T. The main reason might be a proximity type effect in which a small amount of high Tc materials is able to raise the effective Tc of the samples, However such an effect could be suppressed at high field.

Angular Dependent Critical Fields in NbTi-Ge Superlattices in the Weakly Localized Regime

1986 ◽  
Vol 77 ◽  
Author(s):  
Ben Y. Jin ◽  
J. B. Ketterson ◽  
J. E. Hilliard ◽  
E. J. McNiff ◽  
S. Foner ◽  
...  
Keyword(s):  
Diffusion Equation ◽  
Boundary Conditions ◽  
Angular Dependence ◽  
Critical Field ◽  
Upper Critical Field ◽  
Interaction Effects ◽  
Critical Fields ◽  
Gauge Invariant ◽  
Upper Critical Fields ◽  
Lowest Eigenvalue

ABSTRACTThe angular dependence of the upper critical fields, Hc(θ) for a set of NbTi-Ge superlattices were studied at various temperatures. The behavior of Hc(θ) at lower temperatures deviates from the Tinkham expression which is expected to be valid only in the Ginzberg-Landau regime close to Tc. We examine a model for calculating Hc(θ) involving the lowest eigenvalue of the gauge invariant diffusion equation (subject to boundary conditions appropriate to a slab) in the de Gennes expression for the upper critical field of a dirty superconductor at all temperatures. The disorder related localization and interaction effects as well, as the paramagnetic limiting effect, are also considered.

The effect of epitaxy on the upper critical fields of evaporated niobium films

1989 ◽  
Vol 4 (2) ◽  
pp. 283-287 ◽  
Author(s):  
Gin-ichiro Oya ◽  
Tetsuro Komukai ◽  
Yasuji Sawada
Keyword(s):  
Single Crystal ◽  
Critical Field ◽  
Surface Effect ◽  
Upper Critical Field ◽  
Critical Fields ◽  
Surface Nucleation ◽  
Single Crystal Films ◽  
Crystal Films ◽  
Upper Critical Fields ◽  
Niobium Suboxide

Two upper critical fields normal (Bc2⊥) and parallel (Bc2∥) to the surfaces of both single-crystal and polycrystalline Nb films are studied at 4.2 K in relation to the purity and morphology of the films, in order to make properties of the single-crystal films clear. High-quality single-crystal Nb films (with transition temperature Tc of ∼9.3 K and normal resistivity ρn of ∼0.2 μΩ · cm) are found to have magnetic properties characterized by Bc2⊥ of 0.31 T as low as Bc2 (bulk upper critical field) of bulk Nb, and Bc2∥/Bc2⊥ of ∼1.85 as high as Bc3/Bc2 (where Bc3 is the surface nucleation critical field) of pure Nb. These properties depend strongly on high purity and surface smoothness of the films, which is naturally accompanied by superconductivity. Polycrystalline Nb films have higher Bc2⊥ and lower Bc2∥/Bc2⊥, which result from a decrease in purity of the films and a presence of normal-conducting niobium-suboxide layers at the surfaces of the films, and thereby a decrease of the surface effect in the films.

UPPER CRITICAL FIELD OF UNCONVENTIONAL SUPERCONDUCTORS FROM CHEMICAL EQUILIBRIUM

1999 ◽  
Vol 13 (29n31) ◽  
pp. 3443-3448 ◽  
Author(s):  
A. KALLIO ◽  
J. HISSA ◽  
T. HÄYRYNEN ◽  
V. BRÄYSY
Keyword(s):  
Magnetic Field ◽  
Critical Field ◽  
Normal State ◽  
Chemical Equilibrium ◽  
Critical Density ◽  
Upper Critical Field ◽  
Universal Function ◽  
Zero Magnetic Field ◽  
Mathematical Treatment ◽  
Critical Fields

We have shown previously that many normal state properties of high Tc superconductors in zero magnetic field can be understood in terms of a single universal function f(t) in the scaled variable t=T/T*, where T* is connected with temperature independent gap 2Δ=2kBT*, which gives the binding energy of a pair in analogy with dissociation of molecules. The function f(t) determines the fraction of bosons (B++) and fermions (h+) at temperature T and it is obtained from the mathematical treatment of chemical equilibrium with respect to the reaction B++⇌ 2h+. Since for magnetic fields of reasonable strength the Zeeman energy is much smaller than the pseudo gap Δ~100K-800K, the function f(t) in the normal state is largely independent of magnetic field. The main effect of the magnetic field is to increase the tendency for bosons to localize. This means that the critical density nL for delocalization in the ab-plane direction and the critical density for superfluidity nc (≳ nL) both increase with magnetic field. This causes the corresponding temperatures TBL(H) and Tc(H) to go down with the field. Assuming a power law dependence nc(H)/nc(0)=1+AHμ, the upper critical fields for several heavy fermion compounds are shown to fall into a single curve. The purpose here is to show that the upper critical field Hc2(y) (y=Tc(H)/Tc(0)) can be expressed in a simple way in terms of f(t). We show that this theory predicts all the shapes of Hc2(y) observed in several unconventinal superconductors such as Tl 2 Ba 2 CuO 6+δ, with Tc=15 K.

scholarly journals Type-II Ising pairing in few-layer stanene

Science ◽  
2020 ◽  
Vol 367 (6485) ◽  
pp. 1454-1457 ◽  
Author(s):  
Joseph Falson ◽  
Yong Xu ◽  
Menghan Liao ◽  
Yunyi Zang ◽  
Kejing Zhu ◽  
...  
Keyword(s):  
Symmetry Breaking ◽  
Upper Critical Field ◽  
Distinct Type ◽  
Inversion Symmetry ◽  
Spin Orbit Coupling ◽  
Type Ii ◽  
Spin Orbit ◽  
Pairing Mechanism ◽  
Topological Materials ◽  
Ultralow Temperature

Spin-orbit coupling has proven indispensable in the realization of topological materials and, more recently, Ising pairing in two-dimensional superconductors. This pairing mechanism relies on inversion symmetry–breaking and sustains anomalously large in-plane polarizing magnetic fields whose upper limit is predicted to diverge at low temperatures. Here, we show that the recently discovered superconductor few-layer stanene, epitaxially strained gray tin (α-Sn), exhibits a distinct type of Ising pairing between carriers residing in bands with different orbital indices near the Γ-point. The bands are split as a result of spin-orbit locking without the participation of inversion symmetry–breaking. The in-plane upper critical field is strongly enhanced at ultralow temperature and reveals the predicted upturn.

Anisotropic Upper Critical Field of Single Crystal RNi2B2C (R = Y, Lu)

1998 ◽  
Vol 12 (29n31) ◽  
pp. 3264-3266 ◽  
Author(s):  
A. C. Du Mar ◽  
K. D. D. Rathnayaka ◽  
D. G. Naugle ◽  
P. C. Canfield
Keyword(s):  
Low Temperature ◽  
Single Crystal ◽  
Critical Field ◽  
Upper Critical Field ◽  
Critical Fields ◽  
Linear Behavior ◽  
Upward Curvature

Measurements of the anisotropic upper critical field curves have been extended for YNi 2B2C and LuNi2B2C (T c = 15.6 K and 16.1 K, respectively). Measurements of R(T, H) were taken along the crystallographic directions of <100> and <110>. The resulting critical fields show an upward curvature near T c and a linear behavior at low temperature, which continues to below 2 K with little, if any, sign of saturation.

Huge Upper Critical Field and Electronic Instability in Pressure-induced Superconductor CeIrSi3without Inversion Symmetry in the Crystal Structure

2008 ◽  
Vol 77 (7) ◽  
pp. 073705 ◽  
Author(s):  
Rikio Settai ◽  
Yuichiro Miyauchi ◽  
Tetsuya Takeuchi ◽  
Florence Lévy ◽  
Ilya Sheikin ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Critical Field ◽  
Upper Critical Field ◽  
Inversion Symmetry

Evolution of the upper critical field and superconducting vortex phase with thickness in PLD-grown Ta fllms

2022 ◽  
Author(s):  
Yixin Liu ◽  
Han Zhang ◽  
Xiaowen Han ◽  
Teng Wang ◽  
Lingling Wang ◽  
...  
Keyword(s):  
Critical Field ◽  
Three Dimensional ◽  
Anisotropy Parameter ◽  
Upper Critical Field ◽  
Superconducting Devices ◽  
Liquid Region ◽  
Superconducting Transition ◽  
Critical Fields ◽  
Residual Resistance ◽  
20 Nm

Abstract High quality superconducting thin films are the basis for the application of superconducting devices. Here we report the fllm growth and superconducting properties of the Ta films. The films were grown by the pulsed laser deposition technique on the α-Al2O3 substrates. It is found that, with the increase of the fllm thickness from 20 nm to 61 nm, both the superconducting transition temperature Tc and residual resistance ratio RRR display an upward trend, while the upper critical field decreases monotonously in a wide temperature region. A clear anisotropic behavior is revealed by comparing the upper critical fields with two difierent orientations (H ⊥ film and H // film). The anisotropy parameter Γ is found to be as high as 20 for the sample with the thickness of 20 nm. The systematical evolution from two- to three-dimensional features for the superconductivity with the increase of fllm thickness is observed in the temperature dependent upper critical fleld data. Moreover, the vortex liquid region tends to expand with the increase of the fllm thickness.

DETERMINATIONS OF UPPER CRITICAL FIELDS IN CONTINUOUS GINZBURG–LANDAU MODEL

2004 ◽  
Vol 15 (06) ◽  
pp. 783-807
Author(s):  
L. WANG ◽  
H. S. LIM ◽  
C. K. ONG
Keyword(s):  
Critical Field ◽  
Eigenvalue Problems ◽  
Upper Critical Field ◽  
Critical Fields ◽  
Ginzburg Landau ◽  
Direction Parallel ◽  
Landau Model ◽  
The Magnetic Field ◽  
Good Agreement

Novel procedures to determine the parallel upper critical field Bc2 (one-dimensional, 1D) have been proposed within a continuous Ginzburg–Landau model. Unlike conventional methods, where Bc2 is obtained through the determination of the smallest eigenvalue of an appropriate eigen equation, the square of the magnetic field is treated as eigenvalue problems by two procedures so that the upper critical field can be directly deduced. The two procedures proposed are extended to determine the upper critical field in the c–a crystal plane (two-dimensional, 2D) with an arbitrary angle θ tilted from the c-axis. The calculated Bc2 from the two procedures are consistent with each other in both 1D and 2D cases. Moreover, the values of Bc2 near the direction parallel to the layers obtained in the 2D case well approximate the counterparts in the 1D case. The properties of the calculated Bc2 are in reasonably good agreement with existing theories and experiments. The profiles of the order parameters associated with Bc2 for both 1D and 2D cases are Gaussian-like, further validating the methodology proposed.

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