Rashba effect and enriched spin-valley coupling in 
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Zhang, Qingyun; Schwingenschlögl, Udo

doi:10.1103/physrevb.97.155415

Cited by 68 publications

(47 citation statements)

References 54 publications

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“…This figure represents the typical behavior of all the superconducting films investigated here. It should be noted that the superconducting transitions for these HEA films are remarkably sharp even in large magnetic fields, especially when compared with other binary alloys [34,35]. The transition temperatures shift to lower values with increasing field.…”

Section: Parameters Characterizing the Superconducting Statementioning

confidence: 82%

Preparation and characterization of high-entropy alloy (TaNb)1−x(ZrHfTi)x superconducting films

Zhang

Winter

Witteveen

et al. 2020

Phys. Rev. Research

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We report on the preparation and the physical properties of superconducting (TaNb) 1− (ZrHfTi) high-entropy alloy films. The films were prepared by means of magnetron sputtering at room temperature, with ranging from 0 to 1 with an average thickness of 600 -950 nm. All films crystallize in a pseudo body-centered cubic (BCC) structure. For samples with < 0.65, the normal-state properties are metallic, while for ≥ 0.65 the films are weakly insulating. The transition from metallic to weakly insulating occurs right at the near-equimolar stoichiometry. We find all films, except for = 0 or 1, to become superconducting at low temperatures, and we interpret their superconducting properties within the Bardeen-Cooper-Schrieffer (BCS) framework. The highest transition temperature Tc = 6.9 K of the solid solution is observed for ~0.43. The highest upper-critical field Bc2(0) = 11.05 T is found for the near-equimolar ratio ~0.65, where the mixing entropy is the largest. The superconducting parameters derived for all the films from transport measurements are found to be close to those that are reported for amorphous superconductors. Our results indicate that these films of high-entropy alloys are promising candidates for superconducting device fabrication.

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Section: Parameters Characterizing the Superconducting Statementioning

confidence: 82%

Preparation and characterization of high-entropy alloy (TaNb)1−x(ZrHfTi)x superconducting films

Zhang

Winter

Witteveen

et al. 2020

Phys. Rev. Research

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“…The bridges prepared from the 100-nm-thick WSi film have a zero-field critical temperature (0) ≈ 4.95 K, which is close to the maximum for amorphous WSi [18][19][20][21], thereby guaranteeing the high quality of our films. The corresponding critical temperature of the 4-nm-thick WSi film is reduced to (0) ≈ 3.42 K, in agreement with Refs.…”

mentioning

confidence: 96%

Strong suppression of the resistivity near the superconducting transition in narrow microbridges in external magnetic fields

Zhang¹,

Lita²,

Smirnov

et al. 2020

Phys. Rev. B

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We have investigated a series of superconducting bridges based on homogeneous amorphous WSi andMoSi films, with bridge widths w ranging from 2 to 1000 and film thicknesses ~ 4 − 6 nm and 100 nm. Upon decreasing the bridge widths below the respective Pearl lengths, we observe in all cases distinct changes in the characteristics of the resistive transitions to superconductivity. For each of the films, the resistivity curves R(B,T) separate at a well-defined and field-dependent temperature * ( ) with decreasing the temperature, resulting in a dramatic suppression of the resistivity and a sharpening of the transitions with decreasing bridge width w. The associated excess conductivity in all the bridges scales as 1⁄ , which may suggest the presence of a highly conducting region that is dominating the electric transport in narrow bridges. We argue that this effect can only be observed in materials with sufficiently weak vortex pinning.It is generally accepted that the superconductivity in superconducting bridges can be suppressed by gradually reducing their dimensions. While sufficiently thick and wide bridges reflect the properties of the bulk material, wide strips with a reduced thickness ≲ (where is the Ginzburg-Landau coherence length) can be viewed as quasi two-dimensional [1]. Their properties are then strongly influenced by the thickness d, with a certain reduction of the transition temperature to a zero-resistance state [2][3][4][5]. Upon further narrowing a bridge down towards to the one-dimensional (1D) limit < , the critical temperature decreases exponentially with the inverse of the cross section of the bridges[6], leading to a transition to insulating state in the 1D limit [6][7][8][9][10].Placing a type-II superconducting strip into an external magnetic field, magnetic-field-induced vortices can exist as long as > 4.4 [11]. In very thin films, vortices can interact in a different way than in their bulk peers, namely via their stray fields in the surrounding space. The characteristic length scale for this interaction is given by the Pearl length = 2 2 ⁄ , which can be substantially larger than the London penetration depth [12]. In wide bridges, where the bridge width w is larger than all length scales that are relevant for superconductivity, the vortex-vortex interactions are long-range logarithmic as a function of distance r for r < , and they determine the superconducting properties in clean enough samples. It has been suggested that in narrow bridges w < , the vortex-vortex interaction becomes short-range exponential for vortex-vortex separations r > w/π [13], thereby excluding aBerezinskii-Kosterlitz-Thouless (BKT) transition [14,15]. While in this low-field limit, surface barriers also play an important role [16], they are negligible in the high-field limit B ~ Bc2. In this letter we study the transition to superconductivity for amorphous superconducting films in this high-field limit, as a function of the bridge width w for w < and w > .We have fabricated micro-bridges based on four amorphous WSi and...

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“…However, this temperature rise was certainly not high enough to vaporize graphene and create a micro-plasma which could also become a light scattering center. [62][63][64] Such mechanism can be further ruled out since no blackbody radiation in the visible wavelength was observed. Based on the above observations and discussions, we can now depict each step of OL.…”

Section: Resultsmentioning

confidence: 99%

Photoacoustic identification of laser-induced microbubbles as light scattering centers for optical limiting in a liquid suspension of graphene nanosheets

et al. 2020

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Liquid suspensions of carbon nanotubes, graphene and transition metal dichalcogenides have exhibited excellent performance in optical limiting. However, the underlying mechanism has remained elusive and is generally ascribed to their superior nonlinear optical properties such as nonlinear absorption or nonlinear scattering. Using graphene as an example, we show that photo-thermal microbubbles are responsible for the optical limiting as strong light scattering centers: graphene sheets absorb incident light and become heated up above the boiling point of water, resulting in vapor and microbubble generation. This conclusion is based on direct observation of bubbles above the laser beam as well as a strong correlation between laser-induced ultrasound and optical limiting. In-situ Raman scattering of graphene further confirms that the temperature of graphene under laser pulses rises above the boiling point of water but still remains too low to vaporize graphene and create graphene plasma bubbles. Photo-thermal bubble scattering is not a nonlinear optical process and requires very low laser intensity. This understanding helps us to design more efficient optical limiting materials and understand the intrinsic nonlinear optical properties of nanomaterials.

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Rashba effect and enriched spin-valley coupling in GaX / MX2 ( M = Mo, W;

Cited by 68 publications

References 54 publications

Preparation and characterization of high-entropy alloy (TaNb)1−x(ZrHfTi)x superconducting films

Preparation and characterization of high-entropy alloy (TaNb)1−x(ZrHfTi)x superconducting films

Strong suppression of the resistivity near the superconducting transition in narrow microbridges in external magnetic fields

Photoacoustic identification of laser-induced microbubbles as light scattering centers for optical limiting in a liquid suspension of graphene nanosheets

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