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HomeSciencePhysicsSuperconducting Vortices Made Without Magnetic Fields

Superconducting Vortices Made Without Magnetic Fields

    Niladri Banerjee1 and Jason W. A. Robinson2

    • 1Blackett Laboratory, Imperial College London, London, UK
    • 2Department of Materials Science & Metallurgy, University of Cambridge, Cambridge, UK

• Physics 16, 47

A quantum section of matter detected in an iron-based superconductor may host Majorana zero modes—quasiparticles which will function constructing blocks for future quantum computer systems.

Figure 1: A traditional type-II superconductor (blue) can enable an exterior magnetic discipline (grey arrows) to penetrate by means of nonsuperconducting areas (black disks). These areas are surrounded by superconducting currents (blue arrows), forming Abrikosov vortices. A superconductor (yellow) that incorporates remoted magnetic impurities (magnetic moments indicated by pink arrows) can develop Yu-Shiba-Rusinov states (shaded areas). Lin and colleagues have proven that the superconductor Fe(Se,Te) (inexperienced) can kind quantum anomalous vortices within the absence of an exterior magnetic discipline [1]. These buildings encompass remoted Fe magnetic moments bordered by superconducting currents.A traditional type-II superconductor (blue) can enable an exterior magnetic discipline (grey arrows) to penetrate by means of nonsuperconducting areas (black disks). These areas are surrounded by superconducting currents (blue arrows), forming Abrikosov v… Show more

Building a quantum pc is difficult, not least because of computational errors that come up from the interplay of the quantum system with its surroundings. In precept, this error drawback will be mitigated in a fault-tolerant strategy referred to as topological quantum computing, which depends on non-Abelian anyons—unique quasiparticles that may exist solely in two dimensions. However, realizing a cloth system that may host such quasiparticles sometimes requires a robust magnetic discipline, which makes system integration difficult. Now Yishi Lin of Fudan University in China and colleagues have detected and manipulated buildings referred to as quantum anomalous vortices (QAVs) within the iron-based superconductor Fe(Se,Te) [1]. Remarkably, these buildings kind within the absence of a magnetic discipline and will theoretically assist non-Abelian anyons often called Majorana zero modes [2].

To perceive QAVs, it’s useful to think about the traditional habits of a superconductor in a magnetic discipline. Famously, the sphere might be expelled from the fabric’s inside by means of a phenomenon referred to as the Meissner impact if the sphere energy is under a important worth. A sort-II superconductor retains superconductivity to increased discipline strengths than this worth by channeling the sphere by means of nonsuperconducting areas often called vortex cores. These areas are surrounded by circulating superconducting currents that defend the sphere on the cores, forming so-called Abrikosov vortices (Fig. 1, high left).

Rather than making use of a magnetic discipline to a superconductor, remoted magnetic impurities will be inserted into the superconductor. Such impurities break the fabric’s time-reversal symmetry and regionally suppress the energy of the electron-pairing interplay accountable for superconductivity, outlined by the magnitude of a key amount often called the order parameter. The result’s a set of localized states referred to as Yu-Shiba-Rusinov states (Fig. 1, high proper). The energies of those states lie within the superconducting hole—a variety of energies which might be forbidden to single electrons in a superconductor. This image is modified within the presence of spin-orbit coupling, which {couples} the magnetic second of every impurity to the angular momentum of superconducting quasiparticles. In that case, there’s a quantized twist of the order parameter round every impurity. This twist varieties QAVs (Fig. 1, backside).

The spontaneous creation of QAVs within the absence of an exterior magnetic discipline has an attention-grabbing analogy. In 1980, physicists noticed the quantum Hall impact—the quantization of the transverse electrical conductance of a two-dimensional electron fuel in a robust magnetic discipline [3]. A longstanding query had been whether or not an identical phenomenon may exist within the absence of a discipline. In 2013, scientists detected such a phenomenon, dubbed the quantum anomalous Hall impact [4].

Lin and colleagues have now instantly noticed QAVs in Fe(Se,Te), a superconductor that has robust spin-orbit coupling and spin-polarized states related to explicit Fe atoms that act as remoted magnetic impurities. The crew cooled crystalline flakes of Fe(Se,Te) by means of their superconducting transition, which happens at about 14 Ok. The researchers then used a extremely delicate instrument referred to as a scanning superconducting quantum interference system (sSQUID) microscope to sense and picture the magnetic flux rising from the flakes.

The crew detected random patterns of vortices paired with antivortices—buildings that differ from vortices solely within the orientation of their circulating currents. These patterns had been noticed at an utilized magnetic discipline weaker than that comparable to a single flux quantum and even within the absence of such a discipline. In this magnetic-field regime, vortices will not be anticipated.

In Lin and colleagues’ experiments, a discipline coil of the sSQUID microscope generated a weak magnetic discipline. This discipline produced a synchronous hysteretic switching of the vorticity—the curl of the stream velocity—related to every vortex and antivortex. Such habits is just like the magnetization switching of a ferromagnet. Furthermore, the superconducting present induced by this weak discipline drove a rotation of the flux strains threading pairs of impurity magnetic moments. This impact is analogous to the current-induced torque noticed in ferromagnets which have spin-orbit coupling [5], and it offers a technique to manipulate these vortices.

Surface states in Fe(Se,Te) have been proven to have a nontrivial topological band construction with accompanying superconductivity [6]. Under these circumstances, Majorana zero modes can theoretically kind contained in the vortex cores of QAVs [7]. Furthermore, the members of a QAV-antivortex pair have reverse vorticities such that they don’t repel one another, in contrast to the Abrikosov vortices seen in typical superconductors. Consequently, it may be potential to make use of QAVs to trade Majorana zero modes in a course of often called braiding, a key requirement for topological quantum computing. A possible subsequent step, subsequently, is to acquire proof for Majorana zero modes in these methods after which to discover the situations wanted to control QAVs, albeit slowly to protect adiabaticity—one other vital requirement for the sort of computing.


  1. Y. S. Lin et al., “Direct observation of quantum anomalous vortex in Fe(Se,Te),” Phys. Rev. X 13, 011046 (2023).
  2. C. Nayak et al., “Non-Abelian anyons and topological quantum computation,” Rev. Mod. Phys. 80, 1083 (2008).
  3. Ok. v. Klitzing et al., “New method for high-accuracy determination of the fine-structure constant based on quantized Hall resistance,” Phys. Rev. Lett. 45, 494 (1980).
  4. C.-Z. Chang et al., “Experimental observation of the quantum anomalous Hall effect in a magnetic topological insulator,” Science 340, 167 (2013).
  5. I. M. Miron et al., “Perpendicular switching of a single ferromagnetic layer induced by in-plane current injection,” Nature 476, 189 (2011).
  6. P. Zhang et al., “Observation of topological superconductivity on the surface of an iron-based superconductor,” Science 360, 182 (2018).
  7. Ok. Jiang et al., “Quantum anomalous vortex and Majorana zero mode in iron-based superconductor Fe(Te,Se),” Phys. Rev. X 9, 011033 (2019).

About the Authors

Image of Niladri Banerjee

Niladri Banerjee is a senior lecturer at Blackett Laboratory at Imperial College London and a steering committee board member of the Atoms to Devices Research Area on the Henry Royce Institute. His experimental analysis focuses on understanding and exploiting novel emergent digital and magnetic phases in low-dimensional supplies for quantum applied sciences. His contributions embody the primary demonstration of a controllable Josephson junction based mostly on unconventional triplet superconductivity.

Image of Jason W. A. Robinson

Jason W. A. Robinson has a professorial chair in supplies physics on the University of Cambridge, UK, the place he’s a joint head of the Department of Materials Science & Metallurgy, director of the Quantum Materials & Devices Group, and codirector of the Centre for Materials Physics. His experimental analysis focuses on growing multifunctional supplies and nanoelectronic units, approaching key issues within the fields of spintronics, superconductivity, and quantum applied sciences. His contributions to those fields embody pioneering research on triplet proximity results at superconductor-magnet interfaces and serving to to determine the subfield of superconducting spintronics.

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