Gap-like feature in the normal state of X(Fe1−xCox)2As2, X = Ba, Sr and Fe1+yTe revealed by Point Contact Spectroscopy

Arham, Hamood Z.; Hunt, Cassandra R.; Park, W. K.; Gillett, J.; Das, Sitikantha D.; Sebastian, Suchitra E.; Xu, Zhijun; Wen, Jinsheng; Lin, Zhi Wei; Li, Qiang; Gu, Genda; Thaler, A.; Bud’ko, Sergey L.; Canfield, Paul C.; Greene, L. H.

doi:10.1088/1742-6596/400/2/022001

Cited by 9 publications

(6 citation statements)

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“…This observation is strikingly similar to the pseudo-gap feature observed in case of the cuprates where the peaks in (dI/dV ) N representing the pseudogap do not shift with temperature [23]. It should also be noted that although the onset temperature of superconductivity is 6 K, the Andreev reflection like features are observed up to 13 K. Similar observation was made earlier in the context of the ferro-pnictide [25,26] and the chalcogenide superconductors [26]. This was attributed to (1) Andreev reflection originating from pre-formed phase incoherent Cooper pairs [24] in the normal state of epitaxial thin films of ferropnictide superconductors [25] and (2)a novel phase of matter not related to superconductivity in the normal state of the iron chalcogenide superconductors [26].…”

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confidence: 88%

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Unconventional superconductivity at mesoscopic point contacts on the 3D Dirac semimetal Cd3As2

et al. 2015

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Since the three dimensional (3D) Dirac semi-metal Cd 3 As 2 exists close to topological phase boundaries, in principle it should be possible to drive it into exotic new phases, like topological superconductors, by breaking certain symmetries. Here we show that the mesoscopic point-contacts between silver (Ag) and Cd 3 As 2 exhibit superconductivity up to a critical temperature (onset) of 6 K while neither Cd 3 As 2 nor Ag are superconductors. A gap amplitude of 6.5 meV is measured spectroscopically in this phase that varies weakly with temperature and survives up to a remarkably high temperature of 13 K indicating the presence of a robust normal-state pseudogap. The observations indicate the emergence of a new unconventional superconducting phase that exists only in a quantum mechanically confined region under a point-contact between a Dirac semi-metal and a normal metal. * These authors contributed equally to the work † ashok@chemistry.iitd.ac.in ‡ goutam@iisermohali.ac.in 1 arXiv:1410.2072v1 [cond-mat.supr-con]

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confidence: 88%

“…(2)a novel phase of matter not related to superconductivity in the normal state of the iron chalcogenide superconductors [26]. However, in the second case the spectral features exhibit a systematic temperature dependence unlike what we observe here.…”

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confidence: 51%

Unconventional superconductivity at mesoscopic point contacts on the 3D Dirac semimetal Cd3As2

et al. 2015

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“…14 that the onset temperature of superconductivity is 6K, however, the AR like features survive upto 13K. Similar observations have been made previously in ferropnictide [53,54] and chacogenide superconductors [54]. There are two possibilities which may give rise to pseudo gap in superconductors: 1) features similar to AR can originate from pre-formed phase incoherent Cooper pairs [55] in normal state of epitaxial thin films of ferro-pnictide superconductors [53] and (2) a novel phase of matter which is unrelated to superconductivity could appear in the normal state of iron chalcogenide superconductors [54].…”

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confidence: 87%

Tip-induced Superconductivity

Howlader,

Sheet

2020

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It is widely believed that topological superconductivity, a hitherto elusive phase of quantum matter, can be achieved by inducing superconductivity in topological materials. In search of such topological superconductors, certain topological insulators (like, Bi 2 Se 3 ) were successfully turned into superconductors by metal-ion (Cu, Pd, Sr, Nb etc. ) intercalation. Superconductivity could be induced in topological materials through applying pressure as well. for example, a pressureinduced superconducting phase was found in the topological insulator Bi 2 Se 3 . However, in all such cases, no conclusive signature of topological superconductivity was found. In this review, we will discuss about another novel way of inducing superconductivity in a non-superconducting topological material -by creating a mesoscopic interface on the material with a non-superconducting, normal metallic tip where the mesoscopic interface becomes superconducting. Such a phase is now known as a tip-induced superconducting (TISC) phase. This was first seen in 2014 on Cd 3 As 2 at IISER Mohali, India. Following that, a large number of other topological materials were shown to display TISC. Since the TISC phase emerges only at a confined region under a mesoscopic point contact, traditional bulk tools for characterizing superconductivity cannot be employed to detect/confirm such a phase. On the other hand, such a point contact geometry is ideal for probing the possible existence of a temperature and magnetic field dependent superconducting energy gap and a temperature and magnetic field dependent critical current. We will review the details of the experimental signatures that can be used to prove the existence of superconductivity even when the "text-book" tests for detecting superconductivity cannot be performed. Then, we will review different systems where a TISC phase could be realized.

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“…Here we present results in which strong electron correlations are detected at high-temperature in the Fe-based superconductors [38][39][40].…”

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confidence: 90%

“…Note the excess conductance remains at high bias to low temperature, and Andreev reflection is observed below T c (after Ref. [38]) Fig. 2 The top squares denote the onset of the excess conductance, above the antiferromagnetic and orthorhombic transitions.…”

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confidence: 98%

Design of New Superconducting Materials, and Point-Contact Spectroscopy as a Probe of Strong Electron Correlations

Greene

Arham

Hunt

et al. 2012

J Supercond Nov Magn

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At this centenary of the discovery of superconductivity, the design of new and more useful superconductors remains as enigmatic as ever. These materials play crucial roles both for fundamental science and applications, and they hold great promise in addressing our global energy challenge. The recent discovery of a new class of high-temperature superconductors has made the community more enthusiastic than ever about finding new superconductors. Historically, these discoveries were almost completely guided by serendipity, and now, researchers in the field have grown into an enthusiastic global network to find a way, together, to predictively design new superconductors. After a short history of discoveries of superconducting materials, we share our own guidelines for searching for hightemperature superconductors. Finally, we show how pointcontact spectroscopy (PCS) is used to detect strong correlations in the normal state, with a focus on the normal state region of the Fe-based superconductors, defining a new region in the phase diagram of Ba(Fe 1−x Co x ) 2 As 2 .Keywords History of superconducting materials · Design of new superconductors · Point-contact spectroscopy · Fe-based superconductors · High-temperature superconductors At this ten carat diamond anniversary (100 years) of the discovery of superconductivity, the silver anniversary (25 years) of the discovery of high-temperature superconductivity, and the blue topaz anniversary (4 years) of the discovery of a new class of high-temperature Fe-based superconductors, it is worth looking back at the history, and modes of discovery of the many classes of known superconductors. We do this not only for historical breadth, but also to see if we can learn to turn our serendipitous discoveries into predictive design of new superconductors. We start with a short history of the field, mention the ubiquitous connection between the tunable superconductors we know of today, their phase diagrams, and demonstrate how we can measure strong correlations in these materials with pointcontact spectroscopy (PCS).The Physics Today article by van Delft and Kes [1] beautifully relates the discovery of superconductivity by Heike Kamerlingh Onnes: The quest for achieving lower temperatures was followed by the curiosity-driven measurements of the resistance of metals at these newly achieved liquid helium temperatures. Mercury was chosen since it was a liquid at room temperature, and therefore easily purified. As described by Stephen Blundell [2], there existed three popular predictions on how the resistance would behave upon approaching absolute zero: Lord Kelvin predicted an insulating up-turn at low temperatures due to a freezing out of charge carriers; Matthiessen thought the resistance would decrease to a finite value; and Dewar predicted a smooth decrease to zero resistance at zero temperature. The abrupt drop in resistance at ∼4 K was a complete surprise! Over the next few decades, the critical temperature slowly increased through systematic tests of elements, alloys and compounds...

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Gap-like feature in the normal state of X(Fe_1−xCo_x)₂As₂, X = Ba, Sr and Fe_1+yTe revealed by Point Contact Spectroscopy

Cited by 9 publications

References 46 publications

Unconventional superconductivity at mesoscopic point contacts on the 3D Dirac semimetal Cd3As2

Unconventional superconductivity at mesoscopic point contacts on the 3D Dirac semimetal Cd3As2

Tip-induced Superconductivity

Design of New Superconducting Materials, and Point-Contact Spectroscopy as a Probe of Strong Electron Correlations

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