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Soumyanarayanan, Anjan

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Soumyanarayanan

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Anjan

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Soumyanarayanan, Anjan

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2013 - 20144

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Author's Publications: search.filters.isAuthorOfPublication.e5011d51-4dab-4904-8d83-c21da1ac375e

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Now showing 1 - 4 of 4
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    Momentum-resolved STM studies of Rashba-split surface states on the topological semimetal Sb
    (Elsevier BV, 2014) Soumyanarayanan, Anjan; Hoffman, Jenny
    Topological materials host protected surface states with locked spin and momentum degrees of freedom. The helical Dirac character of the surface states, of tremendous scientific interest, stems from the interplay of the bulk band structure and surface Rashba spin-orbit interaction. The semimetal Sb offers a pristine platform to examine the Rashba origins of the Dirac-like topological surface states. Here we present an overview of our momentum-resolved scanning tunneling spectroscopy studies of Sb, over an extended (300 meV) energy range, revealing several features characteristic of the emergence of the Dirac-like surface states from a conventional Rashba-type parabolic dispersion. Our work provides a conceptual framework to create and investigate tunable Rashba states with topological properties.
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    Fermi Surface and Pseudogap Evolution in a Cuprate Superconductor
    (American Association for the Advancement of Science (AAAS), 2014) He, Yang; Yin, Yi; Zech, M.; Soumyanarayanan, Anjan; Yee, Michael Manchun; Williams, Tess Lawanna; Boyer, M. C.; Chatterjee, K.; Wise, W. D.; Zeljkovic, Ilija; Kondo, T.; Takeuchi, T.; Ikuta, H.; Mistark, P.; Markiewicz, R. S.; Bansil, A.; Sachdev, Subir; Hudson, E. W.; Hoffman, Jenny
    The unclear relationship between cuprate superconductivity and the pseudogap state remains an impediment to understanding the high transition temperature (Tc) superconducting mechanism. Here, we used magnetic field–dependent scanning tunneling microscopy to provide phase-sensitive proof that d-wave superconductivity coexists with the pseudogap on the antinodal Fermi surface of an overdoped cuprate. Furthermore, by tracking the hole-doping (p) dependence of the quasi-particle interference pattern within a single bismuth-based cuprate family, we observed a Fermi surface reconstruction slightly below optimal doping, indicating a zero-field quantum phase transition in notable proximity to the maximum superconducting Tc. Surprisingly, this major reorganization of the system’s underlying electronic structure has no effect on the smoothly evolving pseudogap.
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    Charge Order Driven by Fermi-Arc Instability in Bi2Sr2-xLaxCuO6+ 
    (American Association for the Advancement of Science (AAAS), 2013) Comin, R.; Frano, A.; Yee, Michael Manchun; Yoshida, Y.; Eisaki, H.; Schierle, E.; Weschke, E.; Sutarto, R.; He, F.; Soumyanarayanan, Anjan; He, Yang; Le Tacon, M.; Elfimov, I. S.; Hoffman, Jenny; Sawatzky, G. A.; Keimer, B.; Damascelli, A.
    The understanding of the origin of superconductivity in cuprates has been hindered by the apparent diversity of intertwining electronic orders in these materials. We combined resonant x-ray scattering (REXS), scanning-tunneling microscopy (STM), and angle-resolved photoemission spectroscopy (ARPES) to observe a charge order that appears consistently in surface and bulk, and in momentum and real space within one cuprate family. The observed wave vectors rule out simple antinodal nesting in the single-particle limit but match well with a phenomenological model of a many-body instability of the Fermi arcs. Combined with earlier observations of electronic order in other cuprate families, these findings suggest the existence of a generic charge-ordered state in underdoped cuprates and uncover its intimate connection to the pseudogap regime.
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    Quantum phase transition from triangular to stripe charge order in NbSe2
    (Proceedings of the National Academy of Sciences, 2013) Soumyanarayanan, Anjan; Yee, Michael Manchun; He, Yang; van Wezel, Jasper; Rahn, Dirk J.; Rossnagel, Kai; Hudson, E. W.; Norman, Michael R.; Hoffman, Jenny
    The competition between proximate electronic phases produces a complex phenomenology in strongly correlated systems. In particular, fluctuations associated with periodic charge or spin modulations, known as density waves, may lead to exotic superconductivity in several correlated materials. However, density waves have been difficult to isolate in the presence of chemical disorder, and the suspected causal link between competing density wave orders and high-temperature superconductivity is not understood. Here we used scanning tunneling microscopy to image a previously unknown unidirectional (stripe) charge-density wave (CDW) smoothly interfacing with the familiar tridirectional (triangular) CDW on the surface of the stoichiometric superconductor NbSe2. Our low-temperature measurements rule out thermal fluctuations and point to local strain as the tuning parameter for this quantum phase transition. We use this quantum interface to resolve two longstanding debates about the anomalous spectroscopic gap and the role of Fermi surface nesting in the CDW phase of NbSe2. Our results highlight the importance of local strain in governing phase transitions and competing phenomena, and suggest a promising direction of inquiry for resolving similarly longstanding debates in cuprate superconductors and other strongly correlated materials.