Professor at the Department of Microtechnology and Nanoscience, Quantum Device Physics Laboratory
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Unconventional Charge–Spin Conversion in Weyl‐Semimetal WTe2, B. Zhao, et al., S.P. Dash, Advanced Materials, 2000818 (2020). News
Observation of charge to spin conversion in Weyl semimetal WTe2 at room temperature, B. Zhao, et al., S.P. Dash, Physical Review Research 2 (1), 013286 (2020). News
Charge-spin conversion signal in WTe2 van der Waals hybrid devices with a geometrical design, B. Zhao, et al., S.P. Dash, Applied Physics Letters 117 (24), 242401 (2020).
Topological insulators (TIs) exhibit a current-induced spin polarization due to spin-momentum locking of massless Dirac Fermions in their surface states. Here we report the room temperature electrical detection of the spin polarization on the surface of BiSe and BiSbTeSe by employing spin sensitive potentiometric measurements.
Room Temperature Electrical Detection of Spin-Polarized Currents in Topological Insulators, A. Dankert et al., S.P. Dash, Nano Letters, 15, 12, 7976 (2015). News article
Origin and evolution of surface spin current in topological insulators, A Dankert, et al., SP Dash, Phys. Rev. B 97, 125414 (2018).
Graphene - Topological Insulator Heterostructures
Room Temperature spin-valve with van der Waals magnetThe discovery of van der Waals (vdW) magnets opened up a new paradigm for condensed matter physics and spintronic technologies. However, the operations of active spintronic devices with vdW magnets are so far limited to cryogenic temperatures, inhibiting its broader practical applications. Here, for the first time, we demonstrate room temperature spin-valve devices using vdW itinerant ferromagnet FeGeTe in heterostructures with graphene. The tunnel spin polarization of the FeGeTe/graphene vdW interface is detected to be significantly large ~ 45 % and negative at room temperature. Lateral spin-valve device design enables electrical control of spin signal and realization of basic building blocks for device application such as efficient spin injection, transport, precession, and detection functionalities. Furthermore, measurements with different magnetic orientations provide unique insights into the magnetic anisotropy of FeGeTe and its relation with spin polarization and dynamics in the heterostructure. These findings open opportunities for the applications of vdW magnet-based all-2D spintronic devices and integrated spin circuits at ambient temperatures.
Van der Waals Magnet based Spin-Valve Devices
at Room Temperature, B. Zhao, et al., S.P. Dash, (2021) preprint @ arXiv:2107.00310
Magnetic proximity effect in graphene in van der Waals heterostructure with CrGeTe
Graphene spin interconnect
Robust spin interconnect with isotropic spin dynamics in chemical vapor deposited graphene layers and boundaries, D Khokhriakov et al, SP Dash, ACS nano 14 (11), 15864-15873 (2020).
Two-dimensional spintronic circuit architectures on large scale graphene, D Khokhriakov, B Karpiak, AM Hoque, SP Dash, Carbon 161, 892-899 (2020). News
Long distance spin communication in chemical vapour deposited graphene, M.V. Kamalakar, et al., S.P. Dash; Nature Communications, 6, 6766 (2015). News
Two-dimensional (2D) crystals offer a unique platform due to their remarkable and contrastingspintronic properties, such as weak spin-orbit coupling (SOC) in graphene and strong SOC in molybdenum disulfide (MoS2). Here we combine graphene and MoS2 in a van der Waals heterostructure (vdWh) to demonstrate the electric gate control of the spin current and spin lifetime at room temperature. Our findings demonstrate an all-electrical spintronic device at room temperature with the creation, transport and control of the spin in 2D materials heterostructures.
Electrical gate control of spin current in van der Waals heterostructures at room temperature.A. Dankert, S.P. Dash; Nature Communications 8, 16093 (2017).News - https://graphene-flagship.eu/field-effect-transistor-using-graphenes-electron-spin
Inversion of spin signal and spin filtering in ferromagnet| hexagonal boron nitride-graphene van der Waals heterostructures; MV Kamalakar et al, SP Dash; Scientific reports 6, 21168 (2016)Enhanced Tunnel Spin Injection into Graphene using CVD Hexagonal Boron Nitride; MV Kamalakar et al, SP Dash; Scientific Reports, 4: 61446 (2014)
Molybdenum disulfide has recently emerged as a promising two-dimensional semiconducting material for nanoelectronic, optoelectronic, and spintronic applications. Here, we investigate the field-effect transistor behavior of MoS2 and elucidate that the presence of a large Schottky barrier at the MoS2/ferromagnet interface is a major obstacle for electronic devices. We circumvent this problem by a reduction in the Schottky barrier height with the introduction of a thin TiO2 tunnel barrier between the ferromagnet and MoS2. This results in an enhancement of the transistor on-state current and an increment in the field-effect mobility.
High Performance Molybdenum Disulfide Field Effect Transistors with Spin Tunnel Contacts
A. Dankert, et al, S.P. Dash; ACS Nano 8 (1), 476 (2014).Nature Communications 8, 16093 (2017).
V.K. Mutta, et al., SP Dash, Small 11 (18), 2209-2216 (2015).
The control and manipulation of the electron spin in semiconductors is central to spintronics, which aims to represent digital information using spin orientation rather than electron charge. Here we demonstrate room-temperature electrical injection of spin polarization into n-type and p-type silicon from a ferromagnetic tunnel contact, spin manipulation using the Hanle effect and the electrical detection of the induced spin accumulation. These results open the way to the implementation of spin functionality in complementary silicon devices and electronic circuits operating at ambient temperature.
Electrical creation of spin polarization in silicon at room temperature, S.P. Dash, et al., Nature 462, 491 (2009).
Most significant breakthroughs in 2009 (3rd on the list) by Physics world. News
Spin-dependent electronic transport is widely used to probe and manipulate magnetic materials and develop spin-based devices. Here we demonstrate electrostatic modification of the magnitude of spin polarization in a silicon quantum well, and detection thereof by means of tunnelling to a ferromagnet, producing prominent oscillations of tunnel magnetoresistance of up to 8%. The electric modification of the spin polarization relies on discrete states in the Si with a Zeeman spin splitting, an approach that is also applicable to organic, carbon-based and other materials with weak spin–orbit interaction.
Oscillatory spin-polarized tunneling from silicon quantum wells controlled by electric field, R. Jansen, B.C. Min, S.P. Dash; Nature Materials 9, 133 (2010).
2D Magnetic Tunnel Junctions
A. Dankert, et al., S. P. Dash, Nano Research, 8(4), 1357–1364 (2015)
Read more about the Saroj Dash Group
Full list of Publications, see Google Scholar here
Link to Chalmers Research, here
Published: Fri 10 Sep 2021.
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