arXiv subjects

D. A. Bandurin

Publications and source records attributed to D. A. Bandurin.

At least 19 recordsLinked to original sources

arXiv2026

Electronic bistability, discontinuous switching and stochasticity in a two-dimensional semiconductor

Bistability - two stable electronic states under the same bias - underlies switching and memory, but is usually absent in transistors and must be engineered through material means: doped tunnel junctions, filaments in memristors, or phase transitions. Here we demonstrate a transistor with intrinsic electronic bistability in a single chemically homogeneous crystal. In dual-gated black phosphorus, whose band gap narrows under a perpendicular electric field due to a giant Stark effect, the gates not only modulate carrier density but also reshape the band profile, forming interband tunnel junctions in the channel. Transport across the two-gate parameter space reveals competing conduction regimes - diffusive, two tunnelling channels and Zener breakdown - whose interplay produces negative differential conductance and transconductance, discontinuous switching, and hysteresis with the state set by gate history. Moreover, the switching remains intrinsically stochastic, yet statistically stable within a narrow range of gate voltages, providing an electrically programmable source of randomness. Devices based on this principle should be realisable in other two-dimensional semiconductors, opening a route to next-generation computing architectures in which nonlinearity, switching, memory and stochasticity are integrated within a single electrostatically programmable element.

cond-mat.mes-hall↗

arXiv2026

Correlated Insulator Moiré Bolometer

Light incident on an insulator is generally not expected to turn it into a metal without invoking intense ultrafast excitation that leads to transient structural transitions. Here we show that magic-angle twisted bilayer graphene tuned to half filling of the moiré band provides a notable exception to this expectation. We find that weak beam of long-wavelength photons, with energies comparable to the flat-band width, selectively heat the low-heat-capacity electronic subsystem, thereby suppressing the correlated gap. This produces a giant resistance change governed not by a persistent photocarrier population, but by the extreme sensitivity of a many-body correlated gap to weak electronic heating. The resulting photon-driven insulator-to-metal transition produces a broadband low-noise photoresponse with voltage responsivity exceeding millivolts per nW of absorbed power. The mechanism is dual to superconducting hot-electron response: radiation-heated electrons suppress a many-body order, but in reverse the correlated insulator melts into a metal, providing robustness to magnetic fields of several tesla and a sharp insulator-to-metal resistive contrast. Our results establish correlated flat-band systems as a platform for ultra-sensitive detection of faint long-wavelength radiation.

cond-mat.mes-hall↗

arXiv2026

Graphene Zero-Bias Sub-Terahertz Turnkey Detector with Above 43 GHz Bandwidth

High-frequency terahertz (THz) detectors are vital for next-generation high-speed wireless communication systems. Graphene, with its high carrier mobility, broadband absorption, and weak electron-phonon coupling, offers great promise for ultra-fast THz photothermoelectric devices. Although graphene-based detectors in the infrared range have shown bandwidths above 500 GHz, extending their operation to the THz range is difficult because long-wavelength radiation does not efficiently couple to the small graphene area. To overcome this issue, THz antennas are often employed; however, their use typically limits system performance to only a few gigahertz due to parasitic effects. In this work, we present an antenna-coupled sub-THz graphene detector with a bandwidth exceeding 43 GHz. We optimized the detector design to minimize losses, match the antenna impedance to the 1 kOhm graphene channel, and maintain zero-bias operation. Importantly, we introduce a compact, turnkey packaged solution. Our results provide a practical route toward high-speed and low-power graphene THz detectors suitable for real-world communication and imaging applications.

cond-mat.mes-hall↗

arXiv2026

Gate-Tunable Photoresponse of Graphene Josephson Junctions at Terahertz Frequencies

Graphene Josephson junctions (JJ) provide a promising platform for ultra-broadband quantum sensing of light owing to graphene's frequency-independent absorption, vanishing electronic heat capacity, and weak electron-phonon coupling, which enable rapid suppression of the critical current through radiation-induced electron heating. Existing investigations have been confined to the microwave and infrared regimes, where competing detector technologies are already established; by contrast, the terahertz (THz) band - where sensitivity is most urgently lacking and no mature quantum sensor exists - has remained largerly unexplored. Here we demonstrate a strong photoresponse of graphene JJs at THz frequencies, establishing a first experimental step towards graphene-based THz quantum sensors. Under low-intensity illumination, we observe a pronounced suppression of the critical current that generates a strong photovoltage (Vph) under current bias. By tracking this Vph and independently measuring the electron temperature as a function of absorbed power, we extract a responsivity of 88 kV W^-1 and a noise-equivalent power of 45 aW Hz^-1/2 at 1.7 K. Furthermore, gate tunability of our JJ enables access to a regime where hysteretic current-voltage characteristics persist up to 0.9 K, offering a potential route toward single-photon THz detection beyond millikelvin (mK) temperatures. These findings establish graphene JJ as a versatile platform for broadband cryogenic radiation sensing and point towards their use as quantum sensors at THz frequencies.

cond-mat.mes-hall↗

arXiv2026

Strongly nonlinear Bernstein modes in graphene reveal plasmon-enhanced near-field magnetoabsorption

Bernstein modes -- hybrid magnetoplasmon excitations arising from the coupling between cyclotron motion and collective oscillations in two-dimensional electron systems -- offer direct access to non-local electrodynamics. These modes can exhibit rich nonlinear behavior akin to strong-coupling phenomena in cavity quantum electrodynamics, but reaching nonlinear regime has remained experimentally challenging. Here we report the observation of nonlinear Bernstein modes in graphene using terahertz excitation with near-field enhancement from embedded metallic contacts. Photoresistance spectroscopy reveals sharp resonances at Bc/2 and Bc/3 that saturate at radiation intensities nearly an order of magnitude lower than the cyclotron resonance. We ascribe this to strong local heating of the electron gas due to resonant excitation of high-amplitude Bernstein magnetoplasmons, associated with a combination of the field-concentration effect of the near field and plasmonic amplification that is resonantly enhanced in the region of Bernstein gaps. Polarization-resolved measurements further confirm the near-field origin: Bernstein resonances are insensitive to circular helicity but strongly depend on the angle of linear polarization, in sharp contrast to the cyclotron resonance response. Our results establish graphene as a platform for nonlinear magnetoplasmonics, opening opportunities for strong-field manipulation of collective electron dynamics, out-of-equilibrium electron transport, and solid-state analogues of cavity quantum electrodynamics.

cond-mat.mes-hall↗

arXiv2025

Interaction-limited conductivity of twisted bilayer graphene revealed by giant terahertz photoresistance

Identifying the microscopic processes that limit conductivity is essential for understanding correlated and quantum-critical states in quantum materials. In twisted bilayer graphene (TBG) and other twist-controlled materials, the temperature dependence of metallic resistivity follows power-law scaling, with the exponent spanning a broad range, rendering standard transport measurements insufficient to unambiguously identify the dominant scattering processes and giving rise to competing interpretations ranging from phonon-limited transport and umklapp scattering to strange metallicity and heavy fermion renormalization. Here, we use terahertz (THz) excitation to selectively raise the electron temperature in TBG while keeping the lattice cold, enabling a direct separation of electron-electron and electron-phonon contributions to resistivity. We observe a giant THz photoresistance, reaching up to 70% in magic-angle devices, demonstrating that electronic interactions dominate transport even in regimes previously attributed to phonons, including the linear-in-temperature resistivity near the magic angle. Away from the magic angle, we observe coexisting photoresistance and robust quadratic-in-temperature resistivity at extremely low carrier densities where standard electron-electron scattering mechanisms (umklapp and Baber inter-band scattering) are kinematically forbidden. Our analysis identifies the breakdown of Galilean invariance in the Dirac-type dispersion as a possible origin of the interaction-limited conductivity, arising from inter-valley electron-electron collisions. Beyond twisted bilayer graphene, our approach establishes THz-driven hot-electron transport as a general framework for disentangling scattering mechanisms in low-density quantum materials.

cond-mat.mes-hall↗

arXiv2025

Enhanced Terahertz Thermoelectricity via Engineered van Hove Singularities and Nernst Effect in Moiré Superlattices

Thermoelectric materials, long explored for energy harvesting and thermal sensing, convert heat directly into electrical signals. Extending their application to the terahertz (THz) frequency range opens opportunities for low-noise, bias-free THz detection, yet conventional thermoelectrics lack the sensitivity required for practical devices. Thermoelectric coefficients can be strongly enhanced near van Hove singularities (VHS), though these are usually difficult to access in conventional materials. Here we show that moiré band engineering unlocks these singularities for THz optoelectronics. Using 2D moiré structures as a model system, we observe strong enhancement of the THz photothermoelectric response in monolayer and bilayer graphene superlattices when the Fermi level is tuned to band singularities. Applying a relatively small magnetic field further boosts the response through the THz-driven Nernst effect, a transverse thermoelectric current driven by the THz-induced temperature gradient. Our results establish moiré superlattices as a versatile platform for THz thermoelectricity and highlight engineered band structures as a route to high-performance THz optoelectronic devices.

cond-mat.mes-hall↗

arXiv2025

Reconstructing Critical Current Density in Josephson Junctions with Phase Non-linearity

In this Letter, we show that the standard Dynes-Fulton analysis, commonly used to reconstruct the critical current density from interference patterns, breaks down in Josephson junctions with nonlinear phase distributions, leading to non-physical artifacts. To address this, we developed a simple iterative reconstruction algorithm and validated it both numerically and experimentally using a planar Josephson junction model. Unlike conventional approaches based on the logarithmic Hilbert transform, the proposed method allows for incorporating prior knowledge about the system and addresses the fundamental issue of ambiguity in reconstructing the critical current density from interference patterns.

cond-mat.supr-con↗

arXiv2025

Inverse Design of Broadband Antennas for Terahertz Devices Based on 2D Materials

Terahertz (THz) technology, a cornerstone of next-generation high-speed communication and sensing, has long been hindered by impedance mismatch challenges that limit device performance and applicability. These challenges become particularly pronounced when ultrasensitive two-dimensional (2D) materials are employed as the device substrate in the THz range, further complicating their integration into real-world applications. Furthermore, conventional antenna designs often fail to provide adequate matching across the extensive THz spectrum. In this work, we tackle these challenges using a procedural generation algorithm to design THz broadband antennas that satisfy specific performance criteria. Namely, the developed inverse design methodology enables customization for the target impedance value, bandwidth, and contact topology requirements. The proposed antenna achieves an improvement of up to 40\% in power transfer efficiency compared to traditional bow-tie antennas under realistic operating conditions. High-fidelity electromagnetic simulations validate these results, confirming the design's practicality for THz applications. This work addresses critical limitations of existing antenna designs and advances the feasibility of high-frequency applications in both communication and sensing.

physics.app-ph↗

arXiv2025

Non-Reciprocal Current-Phase Relation and Superconducting Diode Effect in Topological-Insulator-Based Josephson Junctions

Josephson junctions (JJ) are essential for superconducting quantum technologies and searches of self-conjugate quasiparticles, pivotal for fault-tolerant quantum computing. Measuring the current-phase relation (CPR) in JJ based on topological insulators (TI) can provide critical insights into unconventional phenomena in these systems, such as the presence of Majorana bound states (MBS) and the nature of non-reciprocal transport. However, reconstructing CPR as a function of magnetic field in such JJs has remained experimentally challenging. Here, we introduce a platform for precise CPR measurements in planar JJs composed of NbSe$_2$ and few layer thick Bi$_2$Se$_3$ (TI) as a function of magnetic field. When a single flux quantum $Φ_\mathrm{0}$ threads the junction, we observe anomalous peak-dip-shaped CPR behaviour and non-reciprocal supercurrent flow. We demonstrate that these anomalies stem from the edge-amplified sloped supercurrent profile rather than MBS signatures often invoked to explain puzzles emerging near $Φ_\mathrm{0}$ in TI-based JJ. Furthermore, we show that such a supercurrent profile gives rise to a previously overlooked, robust and tunable Josephson diode effect. These findings establish field-dependent CPR measurements as a critical tool for exploring topological superconducting devices and offer new design principles for non-reciprocal superconducting electronics.

cond-mat.supr-con↗

arXiv2024

Nanopatterning of multicomponent van der Waals heterostructures using atomic force microscopy

Multilayer van der Waals (vdW) heterostructures have become an important platform in which to study novel fundamental effects emerging at the nanoscale. Standard nanopatterning techniques relying on electron-beam lithography and reactive ion etching, widely applied to pattern such heterostructures, however, impose some limitations on the edge accuracy and resolution, as revealed through numerous experiments with vdW quantum dots and point contacts. Here we present an alternative approach for electrode-free nanopatterning of thick multilayer vdW heterostructures based on atomic force microscopy (AFM). By applying an AC voltage of a relatively small frequency (1-10 kHz) between the sharp platinum tip and the substrate, we realize high-resolution ($\lesssim 100$ nm) etching of thick multicomponent heterostructures if the latter are deposited onto graphite slabs. Importantly, unlike more conventional electrode-free local anodic oxidation, our method does not require a special environment with excess humidity, can be applied at ambient conditions, and enables the patterning of multilayer heterostructures composed of graphene, graphite, hexagonal boron nitride (hBN), NbSe$_{2}$, WSe$_{2}$, and more.

cond-mat.mes-hall↗

arXiv2024

Anomalous terahertz photoconductivity caused by the superballistic flow of hydrodynamic electrons in graphene

Light incident upon materials can induce changes in their electrical conductivity, a phenomenon referred to as photoresistance. In semiconductors, the photoresistance is negative, as light-induced promotion of electrons across the band gap enhances the number of charge carriers participating in transport. In superconductors, the photoresistance is positive because of the destruction of the superconducting state, whereas in normal metals it is vanishing. Here we report a qualitative deviation from the standard behavior in metallic graphene. We show that Dirac electrons exposed to continuous wave (CW) terahertz (THz) radiation can be thermally decoupled from the lattice by 50~K which activates hydrodynamic electron transport. In this regime, the resistance of graphene constrictions experiences a decrease caused by the THz-driven superballistic flow of correlated electrons. We analyze the dependencies of the negative photoresistance on the carrier density, and the radiation power and show that our superballistic devices operate as sensitive phonon-cooled bolometers and can thus offer a picosecond-scale response time. Beyond their fundamental implications, our findings underscore the practicality of electron hydrodynamics in designing ultra-fast THz sensors and electron thermometers.

cond-mat.mes-hall↗

arXiv2023

Fundamental limits of few-layer NbSe$_2$ microbolometers at terahertz frequencies

The rapid development of infrared spectroscopy, observational astronomy, and scanning near-field microscopy has been enabled by the emergence of sensitive mid- and far-infrared photodetectors. Owing to their exceptional signal-to-noise ratio and fast photoresponse, superconducting hot-electron bolometers (HEBs) have become a critical component in these applications. While superconducting HEBs are traditionally made from sputtered superconducting thin films like Nb or NbN, the potential of layered van der Waals (vdW) superconductors is untapped at THz frequencies. Here, we report the fabrication of superconducting HEBs out of few-layer NbSe$_2$ microwires. By improving the interface between NbSe$_2$ and metal leads connected to a broadband antenna, we overcome the impedance mismatch between this vdW superconductor and the radio frequency (RF) readout circuitry that allowed us to achieve large responsivity THz detection over the range from 0.13 to 2.5 THz with minimum noise equivalent power of 7~pW$\sqrt{Hz}$. Using the heterodyne sub-THz mixing technique, we reveal that NbSe$_2$ superconducting HEBs are relatively fast and feature a characteristic response time in the nanosecond range limited by the slow heat escape to the bath through a SiO$_2$ layer, on which they are assembled, in agreement with energy relaxation model. Our work expands the family of materials for superconducting HEBs technology, reveals NbSe$_2$ as a promising platform, and offers a reliable protocol for the in-lab production of custom bolometers using the vdW assembly technique.

cond-mat.supr-con↗

arXiv2023

High-mobility compensated semimetals, orbital magnetization, and umklapp scattering in bilayer graphene moire superlattices

Twist-controlled moire superlattices (MS) have emerged as a versatile platform in which to realize artificial systems with complex electronic spectra. Bernal-stacked bilayer graphene (BLG) and hexagonal boron nitride (hBN) form an interesting example of the MS that has recently featured a set of unexpected behaviors, such as unconventional ferroelectricity and electronic ratchet effect. Yet, the understanding of the BLG/hBN MS electronic properties has, at present, remained fairly limited. Here we develop a multi-messenger approach that combines standard magnetotransport techniques with low-energy sub-THz excitation to get insights into the properties of this MS. We show that BLG/hBN lattice alignment results in the emergence of compensated semimetals at some integer fillings of the moire bands separated by van Hove singularities where Lifshitz transition occurs. A particularly pronounced semimetal develops when 8 electrons reside in the moire unit cell, where coexisting high-mobility electron and hole systems feature a strong magnetoresistance reaching 2350 % already at B=0.25 T. Next, by measuring the THz-driven Nernst effect in remote bands, we observe valley splitting, pointing to an orbital magnetization characterized by a strongly enhanced effective g-factor of 340. Last, using THz photoresistance measurements, we show that the high-temperature conductivity of the BLG/hBN MS is limited by electron-electron umklapp processes. Our multi-facet analysis introduces THz-driven magnetotransport as a convenient tool to probe the band structure and interaction effects in vdW materials and provides a comprehension of the BLG/hBN MS.

cond-mat.mes-hall↗

arXiv2022

Single-photon detection using high-temperature superconductors

The detection of individual quanta of light is important for quantum computation, fluorescence lifetime imaging, single-molecule detection, remote sensing, correlation spectroscopy, and more. Thanks to their broadband operation, high detection efficiency, exceptional signal-to-noise ratio, and fast recovery times, superconducting nanowire single-photon detectors (SNSPDs) have become a critical component in these applications. The operation of SNSPDs based on conventional superconductors, which have a low critical temperature ($T_c$), requires costly and bulky cryocoolers. This motivated exploration of other superconducting materials with higher $T_c$ that would enable single-photon detection at elevated temperatures, yet this task has proven exceedingly difficult. Here we show that with proper processing, high-$T_c$ cuprate superconductors can meet this challenge. We fabricated superconducting nanowires (SNWs) out of thin flakes of Bi$_2$Sr$_2$CaCu$_2$O$_{8+δ}$ and La$_{1.55}$Sr$_{0.45}$CuO$_4$/La$_2$CuO$_4$ (LSCO-LCO) bilayer films and demonstrated their single-photon response up to $25$ and $8$ K, respectively. The single-photon operation is revealed through the linear scaling of the photon count rate (PCR) on the radiation power. Both of our cuprate-based SNSPDs exhibited single-photon sensitivity at the technologically-important $1.5$ $μ$m telecommunications wavelength. Our work expands the family of superconducting materials for SNSPD technology, opens the prospects of raising the temperature ceiling, and raises important questions about the underlying mechanisms of single-photon detection by unconventional superconductors.

cond-mat.supr-con↗

arXiv2022

Interlayer electron-hole friction in tunable twisted bilayer graphene semimetal

Charge-neutral conducting systems represent a class of materials with unusual properties governed by electron-hole (e-h) interactions. Depending on the quasiparticles' statistics, band structure, and device geometry these semimetallic phases of matter can feature unconventional responses to external fields that often defy simple interpretations in terms of single-particle physics. Here we show that small-angle twisted bilayer graphene (SA-TBG) offers a highly-tunable system in which to explore interactions-limited electron conduction. By employing a dual-gated device architecture we tune our devices from a non-degenerate charge-neutral Dirac fluid to a compensated two-component e-h Fermi liquid where spatially separated electrons and holes experience strong mutual friction. This friction is revealed through the T^2 resistivity that accurately follows the e-h drag theory we develop. Our results provide a textbook illustration of a smooth transition between different interaction-limited transport regimes and clarify the conduction mechanisms in charge-neutral SA-TBG.

cond-mat.mes-hall↗

arXiv2022

Out-of-equilibrium criticalities in graphene superlattices

In thermodynamic equilibrium, current in metallic systems is carried by electronic states near the Fermi energy whereas the filled bands underneath contribute little to conduction. Here we describe a very different regime in which carrier distribution in graphene and its superlattices is shifted so far from equilibrium that the filled bands start playing an essential role, leading to a critical-current behavior. The criticalities develop upon the velocity of electron flow reaching the Fermi velocity. Key signatures of the out-of-equilibrium state are current-voltage characteristics resembling those of superconductors, sharp peaks in differential resistance, sign reversal of the Hall effect, and a marked anomaly caused by the Schwinger-like production of hot electron-hole plasma. The observed behavior is expected to be common for all graphene-based superlattices.

cond-mat.other↗

arXiv2021

Cyclotron resonance overtones and near-field magnetoabsorption via terahertz Bernstein modes in graphene

Two-dimensional electron systems subjected to a perpendicular magnetic field absorb electromagnetic radiation via the cyclotron resonance (CR). Here we report a qualitative breach of this well-known behaviour in graphene. Our study of the terahertz photoresponse reveals a resonant burst at the main overtone of the CR, drastically exceeding the signal detected at the position of the ordinary CR. In accordance with the developed theory, the photoresponse dependencies on the magnetic field, doping level, and sample geometry suggest that the origin of this anomaly lies in the near-field magnetoabsorption facilitated by the Bernstein modes, ultra-slow magnetoplasmonic excitations reshaped by nonlocal electron dynamics. Close to the CR harmonics, these modes are characterized by a flat dispersion and a diverging plasmonic density of states that strongly amplifies the radiation absorption. Besides fundamental interest, our experimental results and developed theory show that the radiation absorption via nonlocal collective modes can facilitate a strong photoresponse, a behaviour potentially useful for infrared and terahertz technology.

cond-mat.mes-hall↗