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search.filters.applied.f.access: openAccess × Author: Borisenko, Sergey V. ×

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    A Giant Bulk-Type Dresselhaus Splitting with 3D Chiral Spin Texture in IrBiSe
    (Weinheim : Wiley-VCH, 2020) Liu, Zhonghao; Thirupathaiah, Setti; Yaresko, Alexander N.; Kushwaha, Satya; Gibson, Quinn; Xia, Wei; Guo, Yanfeng; Shen, Dawei; Cava, Robert J.; Borisenko, Sergey V.
    Materials with giant spin splitting are desired for spintronic applications. The fabrications of spintronic devices from half metals with one spin direction are often hampered, however, by stray magnetic fields, domain walls, short spin coherence times, scattering on magnetic atoms or magnetically active interfaces, and other characteristics that come along with the magnetism. The surfaces of topological insulators, or Dirac/Weyl semimetals, could be an alternative, but production of high-quality thin films without the presence of the bulk states at the Fermi energy remains very challenging. Here, by utilizing angle-resolved photoemission spectroscopy, a record-high Dresselhaus spin–orbit splitting of the bulk state in the nonmagnetic IrBiSe is found. The band structure calculations indicate that the splitting band is fully spin-polarized with 3D chiral spin texture. As a source of spin-polarized electrons, lightly doped IrBiSe is expected to generate electric-field-controlled spin-polarized currents, free from back scattering, and could host triplet and Fulde–Ferrel–Larkin–Ovchinnikov (FFLO) superconductivity. © 2020 The Authors. Published by WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
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    Quantum-critical scale invariance in a transition metal alloy
    (Berlin : Springer Nature, 2020) Nakajima, Yasuyuki; Metz, Tristin; Eckberg, Christopher; Kirshenbaum, Kevin; Hughes, Alex; Wang, Renxiong; Wang, Limin; Saha, Shanta R.; Liu, I-Lin; Butch, Nicholas P.; Campbell, Daniel; Eo, Yun Suk; Graf, David; Liu, Zhonghao; Borisenko, Sergey V.; Zavalij, Peter Y.; Paglione, Johnpierre
    Quantum-mechanical fluctuations between competing phases induce exotic collective excitations that exhibit anomalous behavior in transport and thermodynamic properties, and are often intimately linked to the appearance of unconventional Cooper pairing. High-temperature superconductivity, however, makes it difficult to assess the role of quantum-critical fluctuations in shaping anomalous finite-temperature physical properties. Here we report temperature-field scale invariance of non-Fermi liquid thermodynamic, transport, and Hall quantities in a non-superconducting iron-pnictide, Ba(Fe1/3Co1/3Ni1/3)2As2, indicative of quantum criticality at zero temperature and applied magnetic field. Beyond a linear-in-temperature resistivity, the hallmark signature of strong quasiparticle scattering, we find a scattering rate that obeys a universal scaling relation between temperature and applied magnetic fields down to the lowest energy scales. Together with the dominance of hole-like carriers close to the zero-temperature and zero-field limits, the scale invariance, isotropic field response, and lack of applied pressure sensitivity suggests a unique quantum critical system unhindered by a pairing instability.
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    One-sign order parameter in iron based superconductor
    (Basel : MDPI, 2012) Borisenko, Sergey V.; Zabolotnyy, Volodymyr B.; Kordyuk, Alexnader A.; Evtushinsky, Danil V.; Kim, Timur K.; Morozov, Igor V.; Follath, Rolf; Büchner, Bernd
    The onset of superconductivity at the transition temperature is marked by the onset of order, which is characterized by an energy gap. Most models of the iron-based superconductors find a sign-changing (s±) order parameter [1–6], with the physical implication that pairing is driven by spin fluctuations. Recent work, however, has indicated that LiFeAs has a simple isotropic order parameter [7–9] and spin fluctuations are not necessary [7,10], contrary to the models [1–6]. The strength of the spin fluctuations has been controversial [11,12], meaning that the mechanism of superconductivity cannot as yet be determined. We report the momentum dependence of the superconducting energy gap, where we find an anisotropy that rules out coupling through spin fluctuations and the sign change. The results instead suggest that orbital fluctuations assisted by phonons [13,14] are the best explanation for superconductivity.