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C. Tang

Publications and source records attributed to C. Tang.

At least 19 recordsLinked to original sources
arXiv2025

Effect of doping on hot-carrier thermal breakdown in perforated graphene metasurfaces

We examine the robustness of the S-shaped current-voltage characteristics associated with hot-carrier-induced electrical breakdown in perforated graphene metasurfaces (PGMs) as a function of doping. The perforation of the graphene layer forms interdigital arrays of graphene microribbons (GMRs) interconnected by graphene nanoribbon (GNR) bridges. These GNR constrictions act as energy barriers for electrons and holes emitted from the GMRs and govern the inter-GMR thermionic current under an applied bias voltage. The doping and the voltage bias establish distinct electron and hole populations in adjacent GMRs. Peltier heating of these carriers within the GMRs increases their effective temperatures, thereby enhancing the inter-GMR current. The resulting positive feedback between carrier heating and current amplification can trigger an electrothermal breakdown, transforming a superlinear current-voltage dependence into an S-shaped characteristic exhibiting negative differential resistance. The degree of electron-hole asymmetry significantly influences this positive feedback and strongly modifies the overall current-voltage response. These results provide a framework for optimizing PGM-based devices employing GMR/GNR architectures, including voltage-controlled fast switches, incandescent emitters, and terahertz bolometric detectors.

cond-mat.mes-hall↗
arXiv2025

Thermal hot-carrier breakdown in metasurface structures based on coplanar arrays of graphene microribbons connected with wide-gap bridges

We analyze the thermal and electrical characteristics of the metasurface consisting of the coplanar interdigital array of the graphene microribbons (GMRs) connected by nanobridges (NBs). These nanobridges could be implemented using graphene nanoribbons (GNRs), single-wall semiconducting carbon nanotubes (CNTs), or black-arsenic-phosphorus (b-AsP) nanostructures. The bias voltage applied between neighboring GMRs indices electron and hole two-dimensional systems in the GMRs and induces thermionic currents flowing through connecting NBs. The resulting self-heating increases thermionic currents providing an effective positive feadback between the carrier effective temperature and the injected currents. This mechanism may lead to thermal breakdown enabling threshold behavior of current-voltage characteristics and resulting in the S-shape of these characteristics. The devices based on the GMR/GNR, GMR/CNT, and GMR/AsP metasurface structures can be used as fast voltage-controlled current switches, sensors, thermal terahertz and infrared sources, and other devices.

cond-mat.mes-hall↗
arXiv2025

Rectification and bolometric terahertz radiation detectors based on perforated graphene structures exhibiting plasmonic resonant response

We propose and evaluate the characteristics of the terahertz (THz) detectors based on perforated graphene layers (PGLs). The PGL structures constitute the interdigital in-plane arrays of the graphene microribbons (GMRs) connected by the sets of narrow constrictions, which form the graphene nanoribbon (GNR) bridges. The PGL detector operation is associated with the rectification and hot-carrier bolometric mechanisms. The excitation of plasmonic oscillations in the GMR-GNR arrays can reinforce these mechanisms. The room temperature PGL detector responsivity and detectivity are calculated as function of the radiation frequency and device structure parameters. The effects of the rectification and hot-carrier mechanisms are compared. The PGL THz detectors under consideration can exhibit highly competitive values of responsivity and detectivity.

cond-mat.mes-hall↗
arXiv2025

Hot-carrier thermal breakdown and S-type current-voltage characteristics in perforated graphene structures

We investigate the carrier transport characteristics of perforated graphene layer (PGL) composed of arrays of interdigital coplanar graphene microribbons (GMRs) connected by graphene nanoribbon (GNR) bridges. We analyze their operation at room-temperature. Under an applied bias voltage, two-dimensional electron and hole systems (2DES and 2DHS) form in adjacent GMRs. The terminal current in these PGL structures is primarily governed by thermionic transport across the GNR bridges. As electrons and holes traverse the GNRs, they induce heating in the 2DES and 2DHS, creating a positive feedback loop between carrier heating and thermionic emission. This phenomenon, characterized as hot-carrier thermal breakdown, can give rise to S-shaped inter-GMR current-voltage characteristics. These unique transport properties make PGLs promising candidates for fast, voltage-controlled room-temperature switches and electromagnetic radiation detectors.

cond-mat.mes-hall↗
arXiv2024

Detection of terahertz radiation using topological graphene micro-nanoribbon structures with transverse plasmonic resonant cavities

The lateral interdigital array of the graphene microribbons (GMRs) on the h-BN substrate connected by narrow graphene nanoribbon (GNR) bridges serves as an efficient detector of terahertz (THz) radiation. The detection is enabled by the nonlinear GNR elements providing the rectification of the THz signals. The excitation of plasmonic waves along the GMRs (transverse plasmonic oscillations) by impinging THz radiation can lead to a strong resonant amplification of the rectified signal current and substantial enhancement of the detector response. The GMR arrays with the GNR bridges s can be formed by the perforation of uniform graphene layers

cond-mat.mes-hall↗
arXiv2024

Dynamic characteristics of terahertz hot-electron graphene FET bolometers: effect of electron cooling in channel and at side contacts

We analyze the operation of the hot-electron FET bolometers with the graphene channels (GCs) and the gate barrier layers (BLs). Such bolometers use the thermionic emission of the hot electrons heated by incident modulated THz radiation. The hot electron transfer from the GC into the metal gate. As the THz detectors, these bolometers can operate at room temperature. We show that the response and ultimate modulation frequency of the GC-FET bolometers are determined by the efficiency of the hot-electron energy transfer to the lattice and the GC side contacts due to the 2DEG lateral thermal conductance. The dependences of these mechanisms on the band structure and geometrical parameters open the way for the GC-FET bolometers optimization, in particular, for the enhancement of the maximum modulation frequency.

cond-mat.mes-hall↗
arXiv2024

Terahertz plasmonic resonances in coplanar graphene nanoribbon structures

We analyze plasmonic oscillations in the coplanar graphene nanoribbon (GNR) structures induced by the applied terahertz (THz) signals and calculate the GNR impedance. The plasmonic oscillations in the CNR structures are associated with the electron and hole inductances and the lateral inter-CNR capacitance. A relatively low inter-GNR capacitance enables the resonant excitation of the THz plasmonic oscillations in the CNR structures with long GNRs. The GNR structures under consideration can be used in different THz devices as the resonant structures incorporated in THz detectors, THz sources using resonant-tunneling diodes, photomixers, and surface acoustic wave sensors.

cond-mat.mes-hall↗
arXiv2023

Phase- and angle-sensitive terahertz hot-electron bolometric plasmonic detectors based on FETs with graphene channel and composite h-BN/black-P/h-BN gate layer

We propose and analyze the terahertz (THz) bolometric vector detectors based on the graphene-channel field-effect transistors (GC-FET) with the black-P gate barrier layer or with the composite b-BN/black-P/b-BN gate layer. The phase difference between the signal received by the FET source and drain substantially affects the plasmonic resonances. This results in a resonant variation of the detector response on the incoming THz signal phase shift and the THz radiation angle of incidence.

cond-mat.mes-hall↗
arXiv2023

Micromechanical field-effect transistor terahertz detectors with optical interferometric readout

We investigate the response of the micromechanical field-effect transistors (MMFETs) to the impinging terahertz (THz) signals. The MMFET uses the microcantilevers MC as a mechanically floating gate and the movable mirror of the Michelson optical interferometer. The MC mechanical oscillations are transformed into optical signals and the MMFET operates as the detector of THz radiation with the optical output. The combination of the mechanical and plasmonic resonances in the MMFET with the optical amplification enables an effective THz detection.

physics.app-ph↗
arXiv2023

Terahertz bolometric detectors based on graphene field-effect transistors with the composite h-BN/black-P/h-BN gate layers using plasmonic resonances

We propose and analyze the performance of terahertz (THz) room-temperature bolometric detectors based on the graphene channel field-effect transistors (GC-FET). These detectors comprise the gate barrier layer (BL) composed of the lateral hexagonal-Boron Nitride black-Phosphorus/ hexagonal-Boron Nitride (h-BN/b-P/h-BN) structure. The main part of the GC is encapsulated in h-BN, whereas a short section of the GC is sandwiched between the b-P gate BL and the h-BN bottom layer. The b-P gate BL serves as the window for the electron thermionic current from the GC. The electron mobility in the GC section encapsulated in h-BN can be fairly large. This might enable a strong resonant plasmonic response of the GC-FET detectors despite relatively lower electron mobility in the GC section covered by the b-P window BL. The narrow b-P window diminishes the Peltier cooling and enhances the detector performance. The proposed device structure and its operation principle promote elevated values of the room-temperature GC-FET THz detector responsivity and other characteristics, especially at the plasmonic resonances.

cond-mat.mes-hall↗
arXiv2023

Resonant plasmonic detection of terahertz radiation in field-effect transistors with the graphene channel and the black-As$_x$P$_{1-x}$ gate layer

We propose the terahertz (THz) detectors based on field-effect transistors (FETs) with the graphene channel (GC) and the black-Arsenic (b-As) black-Phosphorus (b-P), or black-Arsenic-Phosphorus (b-As$_x$P$_{1-x}$) gate barrier layer. The operation of the GC-FET detectors is associated with the carrier heating in the GC by the THz electric field resonantly excited by incoming radiation leading to an increase in the rectified current between the channel and the gate over the b-As$_x$P$_{1-x}$ energy barrier layer (BLs). The specific feature of the GC-FETs under consideration is relatively low energy BLs and the possibility to optimize the device characteristics by choosing the barriers containing a necessary number of the b-As$_x$P$_{1-x}$ atomic layers and a proper gate voltage. The excitation of the plasma oscillations in the GC-FETs leads to the resonant reinforcement of the carrier heating and the enhancement of the detector responsivity. The room temperature responsivity can exceed the values of $10^3$~A/W. The speed of the GC-FET detector's response to the modulated THz radiation is determined by the processes of carrier heating. As shown, the modulation frequency can be in the range of several GHz at room temperatures.

cond-mat.mes-hall↗
arXiv2023

Hot-electron resonant terahertz bolometric detection in the graphene/black-AsP field-effect transistors with a floating gate

We evaluate the terahertz (THz) detectors based on field effect transistor (FET) with the graphene channel {GC} and a floating metal gate (MG) separated from the GC by a black-phosphorus (b-P) or black-arsenic (b-As) barrier layer (BL). The operation of these GC-FETs is associated with the heating of the two-dimensional electron gas in the GC by impinging THz radiation leading to thermionic emission of the hot electrons from the GC to the MG. This results in the variation of the floating gate potential, which affects the source-drain current. At the THz radiation frequencies close to the plasmonic resonance frequencies in the gated GC, the variation of the source-drain current and, hence, the detector responsivity can be resonantly large.

cond-mat.mes-hall↗
arXiv2023

Effect of electron thermal conductivity on resonant plasmonic detection in the metal/black-AsP/graphene FET terahertz hot-electron bolometers

We analyze the two-dimensional electron gas (2DEG) heating by the incident terahertz (THz) radiation in the field-effect transistor (FET) structures with the graphene channels (GCs) and the black-phosphorus and black-arsenic gate barrier layers (BLs). Such GC-FETs can operate as bolometric THz detectors using the thermionic emission of the hot electrons from the GC via the BL into the gate. Due to the excitation of plasmonic oscillations in the GC by the THz signals, the GC-FET detector response can be pronouncedly resonant, leading to elevated values of the detector responsivity. The lateral thermal conductivity of the 2DEG can markedly affect the GC-FET responsivity, in particular, its spectral characteristics. This effect should be considered for the optimization of the GC-FET detectors.

cond-mat.mes-hall↗
arXiv2022

The Duel of Magnetic Interactions & Structural Instabilities: Itinerant Frustration in the Triangular Lattice Compound LiCrSe$_2$

The recent synthesis of the chromium selenide compound LiCrSe$_2$ constitutes a valuable addition to the ensemble of two-dimensional triangular lattice antiferromagnets (2D-TLA). In this work we present the very first comprehensive study of the combined low temperature nuclear and magnetic structure established in this material. Details on the connection between Li-ion dynamics and structural changes are also presented along with a direct link between atomic structure and spin order via a strong magnetoelastic coupling. LiCrSe$_2$ was found to undergo a first order structural transition from a trigonal crystal system with space group $P\bar{3}m1$ to a monoclinic one with space group $C2/m$ at $T_{\rm s}=30$~K. Such restructuring of the lattice is accompanied by a magnetic transition at $T_{\rm N}=30$~K, with the formation of a complex spin arrangement for the Cr$^{3+}$ moments. Refinement of the magnetic structure with neutron diffraction data and complementary muon spin rotation analysis reveal the presence of two incommensurate magnetic domains with a up-up-down-down arrangement of the spins with ferromagnetic (FM) double chains coupled antiferromagnetically (AFM). In addition to this unusual arrangement, the spin axial vector is modulated both in direction and modulus, resulting in a spin density wave-like order with periodic suppression of the Cr moment along the chains. This behavior is believed to appear as a result of strong competition between direct exchange AFM and superexchange FM couplings established between both nearest neighbor and next nearest neighbor Cr$^{3+}$ ions. We finally conjecture that the resulting magnetic order is stabilized via subtle vacancy/charge order within the Li layers, potentially causing a mix of two different magnetic phases within the sample.

cond-mat.str-el↗
arXiv2020

International Workshop on Next Generation Gamma-Ray Source

A workshop on The Next Generation Gamma-Ray Sources sponsored by the Office of Nuclear Physics at the Department of Energy, was held November 17--19, 2016 in Bethesda, Maryland. The goals of the workshop were to identify basic and applied research opportunities at the frontiers of nuclear physics that would be made possible by the beam capabilities of an advanced laser Compton beam facility. To anchor the scientific vision to realistically achievable beam specifications using proven technologies, the workshop brought together experts in the fields of electron accelerators, lasers, and optics to examine the technical options for achieving the beam specifications required by the most compelling parts of the proposed research programs. An international assembly of participants included current and prospective $\gamma$-ray beam users, accelerator and light-source physicists, and federal agency program managers. Sessions were organized to foster interactions between the beam users and facility developers, allowing for information sharing and mutual feedback between the two groups. The workshop findings and recommendations are summarized in this whitepaper.

nucl-ex↗
arXiv2019

Magnetic domain dynamics in an insulating quantum ferromagnet

The statistics and form of avalanches in a driven system reveal the nature of the underlying energy landscape and dynamics. In conventional metallic ferromagnets, eddy-current back action can dominate the dynamics. Here, we study Barkhausen noise in Li(Ho,Y)F4, an insulating Ising ferromagnet that cannot sustain eddy currents. For large avalanches at temperatures approaching the Curie point, we find a symmetric response free of drag effects. In the low temperature limit, drag effects contribute to the dynamics, which we link to enhanced pinning from local random fields that are enabled by the microscopic dipole-coupled Hamiltonian (the Ising model in transverse field).

cond-mat.other↗
arXiv2018

The Compact Linear Collider (CLIC) - 2018 Summary Report

The Compact Linear Collider (CLIC) is a TeV-scale high-luminosity linear $e^+e^-$ collider under development at CERN. Following the CLIC conceptual design published in 2012, this report provides an overview of the CLIC project, its current status, and future developments. It presents the CLIC physics potential and reports on design, technology, and implementation aspects of the accelerator and the detector. CLIC is foreseen to be built and operated in stages, at centre-of-mass energies of 380 GeV, 1.5 TeV and 3 TeV, respectively. CLIC uses a two-beam acceleration scheme, in which 12 GHz accelerating structures are powered via a high-current drive beam. For the first stage, an alternative with X-band klystron powering is also considered. CLIC accelerator optimisation, technical developments and system tests have resulted in an increased energy efficiency (power around 170 MW) for the 380 GeV stage, together with a reduced cost estimate at the level of 6 billion CHF. The detector concept has been refined using improved software tools. Significant progress has been made on detector technology developments for the tracking and calorimetry systems. A wide range of CLIC physics studies has been conducted, both through full detector simulations and parametric studies, together providing a broad overview of the CLIC physics potential. Each of the three energy stages adds cornerstones of the full CLIC physics programme, such as Higgs width and couplings, top-quark properties, Higgs self-coupling, direct searches, and many precision electroweak measurements. The interpretation of the combined results gives crucial and accurate insight into new physics, largely complementary to LHC and HL-LHC. The construction of the first CLIC energy stage could start by 2026. First beams would be available by 2035, marking the beginning of a broad CLIC physics programme spanning 25-30 years.

physics.acc-ph↗