arXiv subjects

Dmitry Mylnikov

Publications and source records attributed to Dmitry Mylnikov.

7 recordsLinked to original sources

arXiv2026

Large Nernst effect in chemically derived multilayer graphene at millitesla magnetic fields

Simple synthesis of graphitic compounds, their high conductivity, and integrability with other materials motivate the effort toward graphite-based thermoelectric generators. At the same time, semimetallic nature of graphite and graphene results in nearly-zero thermopower due to electron-hole compensation. Here, we observe large transverse thermopower in chemically derived multilayer graphene films with strong fluctuations of thickness and carrier density at low magnetic fields $B$. Using the scanning laser-induced heating of macroscopic film, we find that transverse (Nernst) thermoelectric voltage becomes comparable to the longitudinal thermoelectric voltage at the metal-doped graphene contact at $B^*\approx4$ mT and ambient conditions. Estimates of transverse thermopower $S_{xy}$ based on the known laser-induced temperature show that it is as large as $\sim 10$ $\mu$V/K at $B^*$, and raises in a sub-linear fashion to 250 $\mu$V/K at $B\approx315$ mT, the maximum field we reach with centimeter-sized permanent magnet. Extra increase in thermoelectric signal is achieved upon voltage measurement at Hall probes when the dc field lines are co-directional with local Nernst current. Our results show the promise of large-scale multilayer graphene for thermoelectricity generation.

cond-mat.mes-hall↗

arXiv2026

Universal reconstructive polarimetry with graphene-metal infrared photodetectors

Recent advent of smart photodetectors, where in-situ tuning of responsivity enables the reconstruction of light intensity, polarization and spectrum by a single device, has revolutionized the field of optoelectronics. So far, most such reconstructive detectors were realized with non-scalable technology of van der Waals stacking. Here, we demonstrate the infrared reconstructive polarimetry with photodetectors based on conventional gated graphene-metal junctions. The reconstruction exploits the gate tuning of polarization contrast, which enables the determination of both infrared power and polarization angle from photovoltage measurements at two different gate voltages. The physics enabling the polarimetry lies in polarization-dependent shift of the electron hot spot near the contact, and the gate tuning of photosensitive barrier width. We further show the universality of polarization reconstruction, i.e. its feasibility with different geometries of the junction, and with graphene of different quality, from boron-nitride encapsulated flakes to the scalable chemical vapor deposited films.

cond-mat.mes-hall↗

arXiv2026

Optical losses in pure crystalline silicon in the IR band measured using WGM microresonators

The need for semiconductor technology for crystalline silicon of the highest purity and homogeneity has provided samples exhibiting low optical absorption in the infrared range. Such silicon has become the basis for photonic elements in the telecommunication band, including high-Q microresonators, which are particularly important. However, at longer wavelengths, the loss mechanisms have not yet been sufficiently studied. At the same time, this range is extremely important, especially for biological and medical applications and for fundamental research. We used optical microresonators with whispering gallery modes made from various types of silicon crystals as a tool to study the loss mechanisms. The study involved the pump wavelengths 1.5, 2.6, 6.1, and 8.6 $\mu$m and the maximum measured Q-factors were $1.5\cdot10^9$, $5\cdot10^8$, $1.6\cdot10^7$, and $5\cdot10^4$, respectively. We showed that the conductivity type does not noticeably influence the optical losses, while resistivity and the growing method are defining factors. Our study confirms the utility of WGM microresonators as loss measurement tools and provides significant potential for the development of silicon microresonator-based photonics in the mid-IR band.

physics.optics↗

arXiv2022

Ultralow-noise terahertz detection by p-n junctions in gapped bilayer graphene

Graphene shows a strong promise for detection of terahertz (THz) radiation due to its high carrier mobility, compatibility with on-chip waveguides and transistors, and small heat capacitance. At the same time, weak reaction of graphene's physical properties on the detected radiation can be traced down to the absence of band gap. Here, we study the effect of electrically-induced band gap on THz detection in graphene bilayer with split-gate p-n junction. We show that gap induction leads to simultaneous increase in current and voltage responsivities. At operating temperatures of ~25 K, the responsivity at 20 meV band gap is from 3 to 20 times larger than that in the gapless state. The maximum voltage responsivity of our devices at 0.13 THz illumination exceeds 50 kV/W, while the noise equivalent power falls down to 36 fW/Hz^0.5. These values set new records for semiconductor-based cryogenic terahertz detectors, and pave the way for efficient and fast terahertz detection.

cond-mat.mes-hall↗

arXiv2022

Terahertz photoconductivity in bilayer graphene transistors: evidence for tunneling at gate-induced junctions

Photoconductivity of novel materials is the key property of interest for design of photodetectors, optical modulators, and switches. Despite the photoconductivity of most novel 2d materials has been studied both theoretically and experimentally, the same is not true for 2d p-n junctions that are necessary blocks of most electronic devices. Here, we study the sub-terahertz photocoductivity of gapped bilayer graphene with electrically-induced p-n junctions. We find a strong positive contribution from junctions to resistance, temperature resistance coefficient and photo-resistivity at cryogenic temperatures T ~ 20 K. The contribution to these quantities from junctions exceeds strongly the bulk values at uniform channel doping even at small band gaps ~ 10 meV. We further show that positive junction photoresistance is a hallmark of interband tunneling, and not of intra-band thermionic conduction. Our results point to the possibility of creating various interband tunneling devices based on bilayer graphene, including steep-switching transistors and selective sensors.

cond-mat.mes-hall↗

arXiv2022

Polarization-resolving graphene-based mid-infrared detector

The ability to resolve the polarization of light with on-chip devices represents an urgent problem in optoelectronics. The detectors with polarization resolution demonstrated so far mostly require multiple oriented detectors or movable external polarizers. Here, we experimentally demonstrate the feasibility to resolve the polarization of mid-infrared light with a single chemical-vapor-deposited graphene-channel device with dissimilar metal contacts. This possibility stems from an unusual dependence of photoresponse at graphene-metal junctions on gate voltage and polarization angle. Namely, there exist certain gate voltages providing the polarization-insensitive signal; operation at these voltages can be used for power calibration of the detector. At other gate voltages, the detector features very strong polarization sensitivity, with the ratio of signals for two orthogonal polarizations reaching ~10. Operation at these voltages can provide information about polarization angles, after the power calibration. We show that such unusual gate- and polarization-dependence of photosignal can appear upon competition of isotropic and anisotropic photovoltage generation pathways and discuss the possible physical candidates.

cond-mat.mes-hall↗

arXiv2021

A place for two-dimensional plasmonics in electromagnetic wave detection

Plasmons in two-dimensional electron systems (2DES) feature ultra-strong confinement and are expected to efficiently mediate the interactions between light and charge carriers. Despite these expectations, the electromagnetic detectors exploiting 2d plasmon resonance have been so far inferior to their non-resonant counterparts. Here, we theoretically analyse the origin of these failures, and suggest a proper niche for 2d plasmonics in electromagnetic wave detection. We find that a confined 2DES supporting plasmon resonance has an upper limit of absorption cross-section, which is identical to that of simple metallic dipole antenna. Small size of plasmonic resonators implies their weak dipole moments and impeded coupling to free-space radiation. Achieving the 'dipole limit' of absorption cross-section in isolated 2DES is possible either at unrealistically long carrier momentum relaxation times, or at resonant frequencies below units of terahertz. We further show that amendment of even small metal contacts to 2DES promotes the coupling and reduces the fundamental mode frequency. The contacted resonators can still have deep-subwavelength size. They can be merged into compact arrays of detectors, where signals from elements tuned to different frequencies are summed up. Such arrays may find applications in multi-channel wireless communications, hyper-spectral imaging, and energy harvesting.

cond-mat.mes-hall↗