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Special Seminar
 
Name: Dr. Anand Kumar Roy

Affiliation: Department of Molecular Chemistry and Materials Science, Weizmann Institute of Science, Rehovot, Israel

 Title: Intertwined Quantum States in Topological Semimetal Nanowires and a New Family of All-Metal Core 2D vdW Materials
Date & Time: Monday, 21st April 2025 at 04:00 p.m.
    Venue: Rajarshi Bhattacharyya Memorial Lecture Hall, Chemical Sciences Building
Abstract:
 

Low-dimensional (1D and 2D) quantum materials are emerging as an exciting platform to probe, effectively tune, and engineer new quantum phenomena that are hard to access in bulk materials. Specifically, if made from topological materials, their quasi-1D/2Dgeometry and large surface-to-bulk ratio unlock new expressions of topology and amplifies the role of topological surface states (TSS).These states, located on the material’s surface and edge, host quasiparticles with exceptional properties and potential, including high mobility, giant magnetoresistance, magnetochiral currents, high-speed dissipationless electronics, and realization of Majorana zero modes (MZM) as end states for defect-tolerant quantum computation. Nevertheless, probing and extracting transport features of quasiparticles associated with TSS is strenuous and requires meticulous efforts to enhance the signaturesof these states along with suppressing the contribution from bulk electronic states. To achieve this experimental realization of low-dimensional (1D and 2D) nanostructures of topological materials with a high surface-to-bulk transport ratio is desired. We show a novel synthetic approach to synthesize quasi-1D nanowires (NWs) of topological semimetals, encapsulated in a functional all-around SiO2 dielectric shell and study their electrical and magnetotransport properties. Using topologically rich TaAs2 NWs, we demonstrate thatthe SiO2 shell protects the surface from degradation and can be locally etched to create ohmic contacts at specific locations, while the rest of the NWs surface remains protected, allowing us to probe topologically non-trivial surface states and their magnetotransport features, including metal-to-insulator transition, strong signatures of topologically non-trivial transport at remarkably high temperatures, direction-dependent giant positive and negative magnetoresistance arising from intertwined mixed topological phases, and a double pattern of Aharonov-Bohm oscillations, demonstrating coherent surface transport consistent with the two Dirac cones of a WTI surface. The coexistence and sensitivity of these topological phases to external stimuli are notable and suggest promising applications in spintronics and nanoscale quantum technologies. I will also discuss some of our recent work on a new family of all-metal core 2D vdW materials which offer a plethora of topological and magnetic phases.

References: 

[1] Intertwined Topological Phases in TaAs2 Nanowires with Giant Magnetoresistance and Quantum Coherent Surface Transport. Roy Anand, Eyal, R. M. Skiff, B. Barick, S. D. Escribano, O. Brontvein, K. Rechav, O. Bitton, R. Illan, E. Joselevich. [Abstract%20-%20Copy.pdf]Adv. Mater. [Abstract%20-%20Copy.pdf]2025, 2418279

[2]Halometallenes: A New Family of Two-Dimensional vdW Materials with All-Metal Core.
Tamir Forsht, Anand Roy, Shiyi Gao, Joon Young Park, Kierstin Torres, Roni Gofman, Yuval Nitzav, Shahar Simon, Ayelet Zalic, Nag Pranab Kumar, Linda Wagner, Ifat Kaplan-Ashiri, Katya Rechav, Lothar Houben, Irit Goldian, Sidney Cohen, Hagai Cohen, Takashi Taniguchi, Kenji Watanabe, Haim Beidenkopf, Binghai Yan, Hadar Steinberg, Amit Kanigel, Philip Kim, Ernesto Joselevich. Manuscript soon to be submitted