Ramamoorthy, Harihara

Loading...
Thumbnail Image
Preferred name
Ramamoorthy, Harihara
Alternative Name
Ramamoorthy, H.
Main Affiliation
Email
harihara.ra@kmitl.ac.th

Settings

Now showing 1 - 2 of 2
  • Loading...
    Thumbnail Image
    Some of the metrics are blocked by your 
    consent settings
    Item type:Publication,
    "freeing" Graphene from Its Substrate: Observing Intrinsic Velocity Saturation with Rapid Electrical Pulsing
    (2016-01-13)
    Ramamoorthy, H.
    ;
    Somphonsane, R.
    ;
    Radice, J.
    ;
    He, G.
    ;
    Kwan, C. P.
    Rapid (nanosecond-scale) electrical pulsing is used to study drift-velocity saturation in graphene field-effect devices. In these experiments, high-field pulses are utilized to drive graphene"s carriers on time scales much faster than that on which energy loss to the underlying substrate can occur, thereby allowing the observation of the highest saturation velocities reported to date. In a dramatic departure from the behavior exhibited by conventional metals and semiconductors, as the electron or hole density is reduced toward the charge-neutrality point, the drift velocity is found to reach values comparable to the Fermi velocity itself. Corresponding current densities are as large as 10<sup>9</sup> A/cm<sup>2</sup>, similar to the values reported for carbon nanotubes and for graphene-on-diamond transistors. In essence, our approach of rapid pulsing allows us to "free" graphene from the deleterious influence of its substrate, revealing a pathway to achieve the superior electrical performance promised by this material. The usefulness of this approach is not merely limited to graphene but should extend also to a broad variety of two-dimensional semiconductors.
  • Loading...
    Thumbnail Image
    Some of the metrics are blocked by your 
    consent settings
    Item type:Publication,
    Mesoscopic Interference of Rotated Spins in Graphene Coupled to High-Spin–Orbit-Coupling Substrates
    (2025-11-05)
    Yokoi, Kazushi
    ;
    Somphonsane, Ratchanok
    ;
    Ramamoorthy, Harihara
    ;
    Arabchigavkani, Nargess
    ;
    He, Keke
    We explore the manifestations of spin rotation in graphene in proximity with two different types of high-spin–orbit-coupling (SOC) materials (ferromagnetic Co and nominally diamagnetic WSe<inf>2</inf>). Using weak antilocalization (WAL) as a probe of the induced rotation, we demonstrate that spin interference exhibits a highly stochastic (nonself-averaging) character in the mesoscopic limit. At low temperatures (<20 K), the spin rotation is manifested as a zero-bias peak (or zero-bias anomaly, ZBA) in the differential conductance, a feature that, as expected for WAL, is suppressed by fairly modest magnetic fields (<∼10<sup>2</sup>mT). The ZBA moreover exhibits a stochastic variation when a gate voltage is used to sweep the Fermi level through the graphene bands, with ranges for which the antilocalization is either prominent or strongly suppressed. This mesoscopic character is exhibited by both of the studied systems, whose ZBA is also damped in similar fashion with increasing temperature. We thus provide fundamental insight into the nonensemble-averaged (nonself-averaged) character of spin interference in mesoscopic systems with strong SOC and, more specifically, into how the details of spin rotation are impacted by external gating. This understanding may ultimately enable the efficient modulation of spin currents in future spintronic devices.