People
Research Fellow
Mikhail Kravtsov
Title
Research Fellow
Degree
PhD
Office Location
S9-08-01-37
I-FIM Publications:
2026 |
Elesin, L; Shilov, A L; Kravtsov, M; Zhou, X; Lukianov, M; Kuksov, A; Jana, S; Iorsh, I; Izmaylov, R; Shein, K; Gayduchenko, I; Taniguchi, T; Watanabe, K; Novoselov, K S; Goltsman, G N; Principi, A; Bandurin, D A Correlated insulator Moiré bolometer NATURE COMMUNICATIONS, 17 (1), 2026, DOI: 10.1038/s41467-026-76389-4. @article{WOS:001869851900007, title = {Correlated insulator Moiré bolometer}, author = {L Elesin and A L Shilov and M Kravtsov and X Zhou and M Lukianov and A Kuksov and S Jana and I Iorsh and R Izmaylov and K Shein and I Gayduchenko and T Taniguchi and K Watanabe and K S Novoselov and G N Goltsman and A Principi and D A Bandurin}, doi = {10.1038/s41467-026-76389-4}, times_cited = {0}, year = {2026}, date = {2026-08-01}, journal = {NATURE COMMUNICATIONS}, volume = {17}, number = {1}, publisher = {NATURE PORTFOLIO}, address = {HEIDELBERGER PLATZ 3, BERLIN, 14197, GERMANY}, abstract = {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 moir & eacute; band provides a notable exception to this expectation. We find that weak 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 ultrasensitive detection of faint long-wavelength radiation.}, keywords = {}, pubstate = {published}, tppubtype = {article} } 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 moir & eacute; band provides a notable exception to this expectation. We find that weak 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 ultrasensitive detection of faint long-wavelength radiation.
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Shilov, A L; Elesin, L; Kravtsov, M; Covey, J; Ganichev, S D; Kashchenko, M A; Popova, O; Izmaylov, R; Shein, K; Gayduchenko, I; Zhou, X; Yahniuk, I; Taniguchi, T; Watanabe, K; Berdyugin, A I; Wang, Y; Perebeinos, V; Svintsov, D A; Novoselov, K S; Principi, A; Maslov, D L; Bandurin, D A Interaction-limited conductivity of twisted bilayer graphene revealed by giant terahertz photoresistance NATURE COMMUNICATIONS, 17 (1), 2026, DOI: 10.1038/s41467-026-76554-9. @article{WOS:001874211200016, title = {Interaction-limited conductivity of twisted bilayer graphene revealed by giant terahertz photoresistance}, author = {A L Shilov and L Elesin and M Kravtsov and J Covey and S D Ganichev and M A Kashchenko and O Popova and R Izmaylov and K Shein and I Gayduchenko and X Zhou and I Yahniuk and T Taniguchi and K Watanabe and A I Berdyugin and Y Wang and V Perebeinos and D A Svintsov and K S Novoselov and A Principi and D L Maslov and D A Bandurin}, doi = {10.1038/s41467-026-76554-9}, times_cited = {0}, year = {2026}, date = {2026-08-01}, journal = {NATURE COMMUNICATIONS}, volume = {17}, number = {1}, publisher = {NATURE PORTFOLIO}, address = {HEIDELBERGER PLATZ 3, BERLIN, 14197, GERMANY}, abstract = {Identifying the microscopic processes limiting conductivity is essential for understanding correlated quantum materials. In twisted bilayer graphene, metallic resistivity follows rho similar to T-alpha with widely varying alpha, fueling competing interpretations from phonon-limited transport and umklapp scattering to strange metallicity and heavy-fermion renormalization. Here, we use terahertz excitation to selectively heat electrons while keeping the lattice cold, separating electron-electron from electron-phonon contributions to resistivity. We observe a giant terahertz photoresistance - reaching several k Omega - showing that electron-electron scattering remains significant even in regimes previously attributed to phonons, including the linear-in-T resistivity near the magic angle. Away from it, photoresistance coexists with quadratic-in-T resistivity at low carrier densities where umklapp and Baber scattering are kinematically forbidden. We identify the breakdown of Galilean invariance in the Dirac dispersion, enabling inter-valley electron-electron collisions, as a possible origin. Our approach establishes terahertz-driven hot-electron transport as a framework for disentangling scattering mechanisms in low-density quantum materials.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Identifying the microscopic processes limiting conductivity is essential for understanding correlated quantum materials. In twisted bilayer graphene, metallic resistivity follows rho similar to T-alpha with widely varying alpha, fueling competing interpretations from phonon-limited transport and umklapp scattering to strange metallicity and heavy-fermion renormalization. Here, we use terahertz excitation to selectively heat electrons while keeping the lattice cold, separating electron-electron from electron-phonon contributions to resistivity. We observe a giant terahertz photoresistance - reaching several k Omega - showing that electron-electron scattering remains significant even in regimes previously attributed to phonons, including the linear-in-T resistivity near the magic angle. Away from it, photoresistance coexists with quadratic-in-T resistivity at low carrier densities where umklapp and Baber scattering are kinematically forbidden. We identify the breakdown of Galilean invariance in the Dirac dispersion, enabling inter-valley electron-electron collisions, as a possible origin. Our approach establishes terahertz-driven hot-electron transport as a framework for disentangling scattering mechanisms in low-density quantum materials.
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Zhou, Xiangyu; Gayduchenko, Igor; Kudriashov, Andrei; Shein, Kirill; Kuksov, Anton; Elesin, Leonid; Kravtsov, Mikhail; Shilov, Artur; Popova, Olga; Jana, Subhajit; Novoselov, Kostya S; Taniguchi, Takashi; Watanabe, Kenji; Goltsman, Gregory; Bandurin, Denis A Gate-Tunable Photoresponse of Graphene Josephson Junctions at Terahertz Frequencies NANO LETTERS, 26 (22), pp. 7435-7442, 2026, DOI: 10.1021/acs.nanolett.6c01483. @article{WOS:001776257400001, title = {Gate-Tunable Photoresponse of Graphene Josephson Junctions at Terahertz Frequencies}, author = {Xiangyu Zhou and Igor Gayduchenko and Andrei Kudriashov and Kirill Shein and Anton Kuksov and Leonid Elesin and Mikhail Kravtsov and Artur Shilov and Olga Popova and Subhajit Jana and Kostya S Novoselov and Takashi Taniguchi and Kenji Watanabe and Gregory Goltsman and Denis A Bandurin}, doi = {10.1021/acs.nanolett.6c01483}, times_cited = {0}, issn = {1530-6984}, year = {2026}, date = {2026-06-01}, journal = {NANO LETTERS}, volume = {26}, number = {22}, pages = {7435-7442}, publisher = {AMER CHEMICAL SOC}, address = {1155 16TH ST, NW, WASHINGTON, DC 20036 USA}, abstract = {Graphene Josephson junctions (JJs) are promising platforms for broadband quantum sensing because graphene combines frequency-independent absorption, ultralow electronic heat capacity, and weak electron-phonon coupling. While previous studies focused on microwave and infrared regimes, the terahertz (THz) range-where highly sensitive quantum detectors remain scarce-has largely remained unexplored. Here, we demonstrate a gate-tunable THz photoresponse in graphene JJs. Low-intensity THz illumination strongly suppresses the critical current, generating a pronounced photovoltage under current bias. From photovoltage measurements and independent electron thermometry, we extract a responsivity of 88 kV W-1 and a noise-equivalent power of 45 aW Hz(-1/2) at 1.7 K. In addition, the hysteretic regime that persists up to 0.9 K suggests a possible route toward single-photon THz detection above millikelvin temperatures. Our results establish graphene JJs as promising candidates for cryogenic THz quantum sensing.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Graphene Josephson junctions (JJs) are promising platforms for broadband quantum sensing because graphene combines frequency-independent absorption, ultralow electronic heat capacity, and weak electron-phonon coupling. While previous studies focused on microwave and infrared regimes, the terahertz (THz) range-where highly sensitive quantum detectors remain scarce-has largely remained unexplored. Here, we demonstrate a gate-tunable THz photoresponse in graphene JJs. Low-intensity THz illumination strongly suppresses the critical current, generating a pronounced photovoltage under current bias. From photovoltage measurements and independent electron thermometry, we extract a responsivity of 88 kV W-1 and a noise-equivalent power of 45 aW Hz(-1/2) at 1.7 K. In addition, the hysteretic regime that persists up to 0.9 K suggests a possible route toward single-photon THz detection above millikelvin temperatures. Our results establish graphene JJs as promising candidates for cryogenic THz quantum sensing.
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Nikolaev, Konstantin G; Ivanov, Artemii; Wen, Han; Wang, Qian; Kravtsov, Mikhail; Bandurin, Denis A; Karim, Nazmul; Novoselov, Kostya S; Andreeva, Daria V One-Spot Synthesized Crystalline Graphene/PANI for Wearable Ionic Transistor Textiles SMALL STRUCTURES, 7 (4), 2026, DOI: 10.1002/sstr.202500904. @article{WOS:001751311800005, title = {One-Spot Synthesized Crystalline Graphene/PANI for Wearable Ionic Transistor Textiles}, author = {Konstantin G Nikolaev and Artemii Ivanov and Han Wen and Qian Wang and Mikhail Kravtsov and Denis A Bandurin and Nazmul Karim and Kostya S Novoselov and Daria V Andreeva}, doi = {10.1002/sstr.202500904}, times_cited = {1}, year = {2026}, date = {2026-04-01}, journal = {SMALL STRUCTURES}, volume = {7}, number = {4}, publisher = {WILEY-V C H VERLAG GMBH}, address = {POSTFACH 101161, 69451 WEINHEIM, GERMANY}, abstract = {Here, we report a one-spot, temperature-controlled AC electropolymerization strategy for converting graphene oxide and aniline into a crystalline, processable reduced graphene oxide (rGO)/polyaniline (PANI) composite for wearable ionic transistor textiles. By tuning the electropolymerization temperature from 4 degrees C to 55 degrees C under a low-frequency triangular AC waveform, followed by mild postreduction, conformal polycrystalline PANI nanodomains are grown directly on rGO sheets. Low-temperature synthesis yields the highest structural ordering and the lowest fraction of protonated imine species, directly linking growth conditions to mixed ionic-electronic transport behavior. The resulting rGO/PANI composite functions as an electrolyte-gated transistor with stable operation and amplified gate response. Furthermore, the composite can be stencil printed onto cotton textiles to realize ratiometric Na+/K+ sensing at constant ionic strength, highlighting its potential for scalable, wearable ion-sensing architectures.}, keywords = {}, pubstate = {published}, tppubtype = {article} } Here, we report a one-spot, temperature-controlled AC electropolymerization strategy for converting graphene oxide and aniline into a crystalline, processable reduced graphene oxide (rGO)/polyaniline (PANI) composite for wearable ionic transistor textiles. By tuning the electropolymerization temperature from 4 degrees C to 55 degrees C under a low-frequency triangular AC waveform, followed by mild postreduction, conformal polycrystalline PANI nanodomains are grown directly on rGO sheets. Low-temperature synthesis yields the highest structural ordering and the lowest fraction of protonated imine species, directly linking growth conditions to mixed ionic-electronic transport behavior. The resulting rGO/PANI composite functions as an electrolyte-gated transistor with stable operation and amplified gate response. Furthermore, the composite can be stencil printed onto cotton textiles to realize ratiometric Na+/K+ sensing at constant ionic strength, highlighting its potential for scalable, wearable ion-sensing architectures.
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2025 |
Kravtsov, M; Shilov, A L; Yang, Y; Pryadilin, T; Kashchenko, M A; Popova, O; Titova, M; Voropaev, D; Wang, Y; Shein, K; Gayduchenko, I; Goltsman, G N; Lukianov, M; Kudriashov, A; Taniguchi, T; Watanabe, K; Svintsov, D A; Adam, S; Novoselov, K S; Principi, A; Bandurin, D A Viscous terahertz photoconductivity of hydrodynamic electrons in graphene 22 NATURE NANOTECHNOLOGY, 20 (1), pp. 51+, 2025, DOI: 10.1038/s41565-024-01795-y. @article{WOS:001330508900002, title = {Viscous terahertz photoconductivity of hydrodynamic electrons in graphene}, author = {M Kravtsov and A L Shilov and Y Yang and T Pryadilin and M A Kashchenko and O Popova and M Titova and D Voropaev and Y Wang and K Shein and I Gayduchenko and G N Goltsman and M Lukianov and A Kudriashov and T Taniguchi and K Watanabe and D A Svintsov and S Adam and K S Novoselov and A Principi and D A Bandurin}, doi = {10.1038/s41565-024-01795-y}, times_cited = {22}, issn = {1748-3387}, year = {2025}, date = {2025-01-01}, journal = {NATURE NANOTECHNOLOGY}, volume = {20}, number = {1}, pages = {51+}, publisher = {NATURE PORTFOLIO}, address = {HEIDELBERGER PLATZ 3, BERLIN, 14197, GERMANY}, abstract = {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 bandgap enhances the number of charge carriers participating in transport. In superconductors and normal metals, the photoresistance is positive because of the destruction of the superconducting state and enhanced momentum-relaxing scattering, respectively. Here we report a qualitative deviation from the standard behaviour in doped metallic graphene. We show that Dirac electrons exposed to continuous-wave terahertz (THz) radiation can be thermally decoupled from the lattice, 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 analyse 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, in principle, 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.}, keywords = {}, pubstate = {published}, tppubtype = {article} } 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 bandgap enhances the number of charge carriers participating in transport. In superconductors and normal metals, the photoresistance is positive because of the destruction of the superconducting state and enhanced momentum-relaxing scattering, respectively. Here we report a qualitative deviation from the standard behaviour in doped metallic graphene. We show that Dirac electrons exposed to continuous-wave terahertz (THz) radiation can be thermally decoupled from the lattice, 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 analyse 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, in principle, 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.
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