arXiv subjects

Naveen Shetty

Publications and source records attributed to Naveen Shetty.

10 recordsLinked to original sources

arXiv2026

Raman scattering of phonon polaritons under nanoscale confinement: the role of structure and environment

Strong light-matter coupling gives rise to polaritons -- quasiparticles that combine both photonic and material characteristics. Here, we show that polar nanocrystals exhibit structure- and environment-dependent Raman scattering, enabled by their hybrid phonon polariton nature. Such dispersive behavior enables refractive index sensing in the mid-infrared range via visible-wavelength inelastic spectroscopy and draws parallels with molecular systems under vibrational strong coupling. Crucially, Raman scattering appears only under nanoscale confinement of phonon polaritons. For optimal structures, this leads to self-hybridization between localized phonon modes and surface phonon polaritons hosted by the same nanoparticle.

physics.optics↗

arXiv2026

Real-Space Plasmon Imaging Reveals Modified Electronic Structure of Gold at the Monolayer Limit

Atomically thin materials exhibit electronic and optical properties distinct from their three-dimensional counterparts. For metals, particularly gold, monolayer studies remain largely unexplored due to fabrication and characterisation challenges. Here we report the first optical study of a stable quasi-freestanding gold monolayer formed by Au intercalation between graphene and SiC. Mid-infrared nanoimaging reveals plasmon-polaritons with wavelengths nearly an order of magnitude shorter than free-space light. Analysis of their dispersion using a Drude model yields a relaxation time of $τ= 18\,$fs, comparable to bulk gold, and a Drude weight of $D = 1.3\,$mS$\cdot$eV, nearly twice the bulk expectation. These results establish monolayer gold as a two-dimensional metal, opening opportunities for nanoscale photonics, plasmonics and ultra-thin electronics.

physics.optics↗

arXiv2025

Wafer-Scale Single-Crystalline Monolayer Graphene

Producing large-area single-crystalline graphene is key to realizing its full potential in advanced applications, including twistronics. Yet, controlling graphene growth kinetics to avoid grain boundaries or multilayer growth remains challenging. Here, we demonstrate single-crystalline graphene free from multilayer domains via one-step delamination of epitaxial graphene from silicon carbide (SiC). This is enabled by a specific surface reconstruction of 4H-SiC(0001) achieved in our growth conditions. High crystalline quality is confirmed by the observation of the half-integer quantum Hall effect -- the hallmark of monolayer graphene -- in near cm-sized crystals. The scalability of our process, explored with 4''-wafers, represents an advance toward large-scale integration of high-performance graphene applications.

cond-mat.mes-hall↗

arXiv2025

Quantum-Ready Microwave Detection with Scalable Graphene Bolometers in the Strong Localization Regime

Exploiting quantum interference of charge carriers, epitaxial graphene grown on silicon carbide emerges as a game-changing platform for ultra-sensitive bolometric sensing, featuring an intrinsic resistive thermometer response unmatched by any other graphene variant. By achieving low and uniform carrier densities, we have accessed a new regime of strong charge localization that dramatically reduces thermal conductance, significantly enhancing bolometer performance. Here we present scalable graphene-based bolometers engineered for detecting GHz-range photons, a frequency domain essential for superconducting quantum processors. Our devices deliver a state-of-the-art noise equivalent power of 40 zW$/\sqrt{\rm Hz}$ at $T=40~$mK, enabled by the steep temperature dependence of thermal conductance, $G_{\rm th}\sim T^4$ for $T<100~$mK. These results establish epitaxial graphene bolometers as versatile and low-back-action detectors, unlocking new possibilities for next-generation quantum processors and pioneering investigations into the thermodynamics and thermalization pathways of strongly entangled quantum systems.

cond-mat.mes-hall↗

arXiv2024

Gate-tunable negative differential resistance in multifunctional van der Waals heterostructure

Two-dimensional (2D) semiconductors have emerged as exciting candidates for the development of low-power and multifunctional computing applications, thanks to their qualities such as layer-dependent band gap tunability, high carrier mobility, and excellent electrostatic control. Here, we explore a pair of 2D semiconductors with nearly broken-gap (Type-III-like) band alignment and demonstrate a highly gate-tunable p-MoTe$_2$/n-SnS$_2$ heterojunction with multifunctional behavior. Employing a dual-gated asymmetric device geometry, we unveil its functionality as both a forward and backward rectifying device. Moreover, we observe a highly gate-tunable negative differential resistance (NDR), with a gate-coupling efficiency of $\eta \simeq 0.5$ and a peak-to-valley ratio of $\sim$ 3 down to 150K. By employing density functional theory, we determine that the observed NDR is dominated by valence band-to-valence band tunneling, while additional interband tunneling contributions arise at higher bias. The combination of tunneling driven transport and gate controllability of NDR opens the pathway for realizing gate-tunable 2D material-based neuromorphic and energy-efficient electronics.

cond-mat.mes-hall↗

arXiv2023

Scalable fabrication of edge contacts to 2D materials

We present a fabrication method for reliably and reproducibly forming electrical contacts to 2D materials, based on the tri-layer resist system. We demonstrate the applicability of this method for epitaxial graphene on silicon carbide (epigraphene) and the transition metal dichalcogenides (TMDCs) molybdenum disulfide ($MoS_2$). For epigraphene, the specific contact resistances are of the order of $ρ_c$ ~ $50$ $Ωμm$, and follow the Landauer quantum limit, $ρ_c \propto n^{-1/2}$, with $n$ being the carrier density of graphene. For $MoS_2$ flakes, our edge contacts enable field effect transistors (FET) with ON/OFF ratio of $> 10^6$ at room temperature ( $> 10^9$ at cryogenic temperatures). The fabrication route here demonstrated allows for contact metallization using thermal evaporation and also by sputtering, giving an additional flexibility when designing electrical interfaces, which is key in practical devices and when exploring the electrical properties of emerging materials.

cond-mat.mes-hall↗

arXiv2022

Exceptionally accurate large graphene quantum Hall arrays for the new SI

The quantum Hall effect (QHE) is a cornerstone in the new International System of Units (SI), wherein the base units are derived from seven fundamental constants such as Planck's constant h and elementary charge e. Graphene has revolutionized practical resistance metrology by enabling the realization of quantized resistance h/2e^2 = 12.9... kOhm under relaxed experimental conditions. Looking ahead, graphene also has the potential to improve realizations of the electronic kilogram using the Kibble balance, and the quantum Ampere in wide current ranges. However, these prospects require different resistance values than practically achievable in single QHE devices, while also imposing stringent demands on energy dissipation in single QHE devices, ultimately requiring currents almost two orders of magnitude higher than the typical QHE breakdown currents IC ~ 100 uA achievable in graphene. Here we present unprecedented accuracy in the quantization of a record sized quantum Hall array (QHA), demonstrating RK/236 ~ 109 Ohm with 0.2 part-per-billion (nOhm/Ohm) accuracy with IC over 5 mA (~ 1 nOhm/Ohm accuracy for IC = 8.5 mA), using epitaxial graphene on silicon carbide (epigraphene). The array quantization accuracy, comparable to the most precise universality tests of QHE in single Hall bar devices, together with the scalability and reliability of this approach pave the road for superior realizations of three key units in the modern SI: the ohm, the ampere, and the kilogram.

cond-mat.mes-hall↗

arXiv2022

Highly efficient UV detection in a metal-semiconductor-metal detector with epigraphene

We show that epitaxial graphene on silicon carbide (epigraphene) grown at high temperatures (T > 1850 °C) readily acts as material for implementing solar-blind ultraviolet (UV) detectors with outstanding performance. We present centimeter-sized epigraphene metal-semiconductor-metal (MSM) detectors with peak external quantum efficiency of ~ 85% for wavelengths 250-280 nm, corresponding to nearly 100% internal quantum efficiency when accounting for reflection losses. Zero bias operation is possible in asymmetric devices, with the responsivity to UV remaining as high as R = 134 mA/W, making this a self-powered detector. The low dark currents Io ~50 fA translate into an estimated record high specific detectivity D = 3.5 x 10^15 Jones. The performance that we demonstrate, together with material reproducibility, renders epigraphene technologically attractive to implement high-performance planar MSM devices with a low processing effort, including multi-pixel UV sensor arrays, suitable for a number of practical applications.

cond-mat.mes-hall↗

arXiv2020

Electron-phonon coupling of epigraphene at millikelvin temperatures

We investigate the basic charge and heat transport properties of charge neutral epigraphene at sub-kelvin temperatures, demonstrating nearly logarithmic dependence of electrical conductivity over more than two decades in temperature. Using graphene's sheet conductance as in-situ thermometer, we present a measurement of electron-phonon heat transport at mK temperatures and show that it obeys the $T^4$ dependence characteristic for clean two-dimensional conductor. Based on our measurement we predict the noise-equivalent power of $\sim 10^{-22}~{\rm W}/\sqrt{\rm Hz}$ of epigraphene bolometer at the low end of achievable temperatures.

cond-mat.mes-hall↗

arXiv2020

The performance limits of epigraphene Hall sensors

Epitaxial graphene on silicon carbide, or epigraphene, provides an excellent platform for Hall sensing devices in terms of both high electrical quality and scalability. However, the challenge in controlling its carrier density has thus far prevented systematic studies of epigraphene Hall sensor performance. In this work we investigate epigraphene Hall sensors where epigraphene is doped across the Dirac point using molecular doping. Depending on the carrier density, molecular-doped epigraphene Hall sensors reach room temperature sensitivities $S_V=0.23 V/VT$,$S_I=1440 V/AT$ and magnetic field detection limits down to $B_{MIN}=27$ $nT/\sqrt{Hz}$ at 20 kHz. Thermally stabilized devices demonstrate operation up to $T=150$ $^oC$ with $S_V=0.12 V/VT$, $S_I=300 V/AT$ and $B_{MIN}\approx 100$ $nT/\sqrt{Hz}$ at 20 kHz.

cond-mat.mtrl-sci↗