Achievement of Superconductivity at Room-Temperature

Scientists from Various Universities (Department of Mechanical Engineering, School of Engineering and Applied Sciences, University of Rochester, Rochester, NY, USA, Department of Physics and Astronomy, University of Rochester, Rochester, NY, USA, Intel Corporation, Hillsboro, OR, USA, Department of Chemistry and Biochemistry, University of Nevada Las Vegas, Las Vegas, NV, USA, Department of Physics and Astronomy, University of Nevada Las Vegas, Las Vegas, NV, USA) and their research collaboration team have discovered a mystery material that conducts electricity without any resistance at a room temperature of up to 15 °C. It is a new record for superconductivity, a phenomenal effect which is usually operated at very cold temperatures. As per the discovery in 2015, the material itself shows the potential of a class of superconductors.

Over the past decades, there was an emerging interest in the discovery of materials relevant to room-temperature superconductivity mainly for the production of sensitive magnetometers based on SQUIDs (superconducting quantum interference devices). Extreme pressure has proven the most versatile order parameter and a mechanism for pressure-induced metallization which facilitates the production of new quantum materials with unique stoichiometries. Although superconductors have a wide variety of applications from magnetic resonance imaging machines to mobile-phone towers, it has a serious limitation, that it survives lone under extremely high pressures which means that it will not have any immediate practical applications. Still the physicists hope for the best to pave the way for the development of zero-resistance materials that can function at lower pressures [1].

Prof. Davide Castelvecchi says that “Material breaks a symbolic barrier – but extreme pressure conditions make it difficult to analyse”. A scientist Mikhail Eremets, from the Max Planck Institute for Chemistry in Mainz, Germany, reported a latest research study, on a convincing evidence of high-temperature conductivity, which was published in Nature on 14^th October 2020. Further he adds the high-pressure, high-temperature superconductor, it indicates a line of work that he started in 2015, a compound that consists of hydrogen and sulfur will have zero resistance up to -70 °C [2].

Ashkan Salamat, a physicist from the University of Nevada, Las Vegas says that a high-pressure compound of hydrogen and lanthanum was shown to be superconductive at –13 °C in 2018. However, the latest research studies showed that, the superconductivity has been seen in a compound of three elements rather than two, the material is made of carbon, sulfur and hydrogen. Adding a third element will greatly broaden the combinations which can be include for future experiments to be searching for new superconductors [3]. Another Physicist Ranga Dias from the University of Rochester in New York, along with Salamat and other collaborators, have reported that the mixture of carbon, hydrogen and sulfur is placed in a microscope and make carved between the tips of two diamonds. They triggered the chemical reactions in the sample through laser light, as crystals are identified. Further, they have lowered the experimental temperature, resistance to current passed through the material dropped to zero, indicating that the sample had become superconductive and found that this transition occurred only at higher temperatures.

Prof. E. Snider and his collaborators have achieved, one of the long-standing challenges in experimental physics is the observation of room-temperature superconductivity in carbonaceous sulfur hydride. The photochemically synthesized C–S–H system becomes superconducting of its highest critical temperature (T_c) being = 287.7 ± 1.2 K and pressure at 267 ± 10 GPa and the temperature probe’s accuracy is ±0.1 K. They noted that with increasing pressure, the resistance of the sample decreases, showing that it becomes more metallic at higher pressure conditions [1].

Figure 1. The superconductivity laboratory at the University of Rochester, New York [1].

Magnetic Susceptibility

A superior test for superconductivity which is usually practiced is the search of a strong diamagnetic transition in the a.c. magnetic susceptibility. The onset of superconductivity is signal to (10–15 nV), with a sharp drop in susceptibility indicates a diamagnetic transition, that shifts to higher temperatures with an increasing pressure. In this way, the highest transition temperature measured is at 198 K (transition midpoint), reached at the highest pressure (measured 189 GPa). The quality of this data is very high and the given small sample size (~80 μm) in diameter and 5–10 μm. Therefore, substantial challenges for measuring properties like magnetic susceptibility suggest a need for novel experimental capabilities, such as spectroscopic techniques or magnetic sensing using nitrogen vacancy centres.

Magnetic-Field Response

For further confirmation, the superconducting transition at higher pressure they exploit the inherent antagonism between an external magnetic field and superconductivity. As per Bardeen–Cooper–Schrieffer theory, an external magnetic field exerts a Lorentz force to the opposite momenta of the electrons in a Cooper pair (the diamagnetic effect)and induces a Zeeman effect polarizing the initially spin-paired states of the pair electrons (the Pauli paramagnetic effect). Both these effects result the breaking of a Cooper pair, thus reducing the critical temperature (T_c) of the material and setting up with an upper critical field (H_c) such as that the superconducting state will survive.

Our SNB team recommended this research article to enrich our viewer’s knowledge to know about the achievement of superconductivity at room-temperature. A very accurate structure determination of hydrogen-rich materials under very high pressure is extremely challenging, and they believed that the structural and stoichiometric determination of super hydride systems will enable the direct probing of elements such as carbon and sulfur. The main key factor that can achieve for very-high-T_c superconductors for the stable (or metastable) at ambient pressure is the ‘Compositional Tuning’ of the C–S–H ternary systems through a controlling molecular exchange at lower pressures. Hence, a robust room-temperature superconducting material will transform the energy economy, quantum information processing and sensing that can be achievable.

References

1. E. Snideret al.,Nature 586, 373(2020).
2. A. P.Drozdov, et al., Nature 525, 73(2015).
3. M. Somayazulu, et al., Phys. Rev. Lett. 122, 027001(2019).

Blog Written By

Dr. Y. Sasikumar

School of Materials Science and Engineering, 

Tianjin University of Technology, China

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