arXiv subjects

M. Reznikov

Publications and source records attributed to M. Reznikov.

14 recordsLinked to original sources

arXiv2021

Skyrmion-(Anti)Vortex Coupling in a Chiral Magnet-Superconductor Heterostructure

We report experimental coupling of chiral magnetism and superconductivity in [IrFeCoPt]/Nb heterostructures. The stray field of skyrmions with radius ~50nm is sufficient to nucleate antivortices in a 25nm Nb film, with unique signatures in the magnetization, critical current and flux dynamics, corroborated via simulations. We also detect a thermally-tunable Rashba-Edelstein exchange coupling in the isolated skyrmion phase. This realization of a strongly interacting skyrmion-(anti)vortex system opens a path towards controllable topological hybrid materials, unattainable to date.

cond-mat.supr-con↗

arXiv2018

Probing spin susceptibility of a correlated two-dimensional electron system by transport and magnetization measurements

We report temperature and density dependences of the spin susceptibility of strongly interacting electrons in Si inversion layers. We measured (i) the itinerant electron susceptibility $χ^*$ from the Shubnikov-de Haas oscillations in crossed magnetic fields and (ii) thermodynamic susceptibility $χ_{\rm T}$ sensitive to all the electrons in the layer. Both $χ^*$ and $χ_{\rm T}$ are strongly enhanced with lowering the electron density in the metallic phase. However, there is no sign of divergency of either quantity at the density of the metal-insulator transition $n_c$. Moreover, the value of $χ_{\rm T}$, which can be measured across the transition down to very low densities deep in the insulating phase, increases with density at $n<n_c$, as expected. In the absence of magnetic field, we found the temperature dependence of $χ^*$ to be consistent with Fermi-liquid-based predictions, and to be much weaker than the power-law, predicted by non-Fermi-liquid models. We attribute a much stronger temperature dependence of $χ_{\rm T}$ to localized spin droplets. In strong enough in-plane magnetic field, we found the temperature dependence of $χ^*$ to be stronger than that expected for the Fermi liquid interaction corrections.

cond-mat.str-el↗

arXiv2017

Zero Energy States at a Normal--Cuprate-Superconductor Interface Probed by Shot Noise

We report measurements of the current noise generated by the optimally doped, x=0.15, ${\rm Au- La_{2-x}Sr_xCuO_4}$ junctions. For high transmission junctions on (110) surface, we observed split zero-bias conductance peak (ZBCP), accompanied by enhanced shot noise. We attribute the enhanced noise to the Cooper pair transport through the junction. The ZBCP disappears and the noise decreases to the one expected for the charge $e$ with heating at temperatures well below ${\rm T_c}$, and at voltages much smaller than the bulk superconducting gap, setting a new energy scale of 0.5 mV. We attribute this scale to the existence of an $id_{xy}$ or $is$ order parameter at the sample surface.

cond-mat.supr-con↗

arXiv2012

Spin-Droplet State of an Interacting 2D Electron System

We report thermodynamic magnetization measurements of two-dimensional electrons in several high mobility Si metal-oxide-semiconductor field-effect transistors. We provide evidence for an easily polarizable electron state in a wide density range from insulating to deep into the metallic phase. The temperature and magnetic field dependence of the magnetization is consistent with the formation of large-spin droplets in the insulating phase. These droplets melt in the metallic phase with increasing density and temperature, although they survive up to large densities.

cond-mat.str-el↗

arXiv2011

Thermodynamic magnetization of two-dimensional electron gas measured over wide range of densities

We report measurements of dm/dn in Si MOSFET, where m is the magnetization of the two-dimensional electron gas and n is its density. We extended the density range of measurements from well in the metallic to deep in the insulating region. The paper discusses in detail the conditions under which this extension is justified, as well as the corrections one should make to extract dm/dn properly. At low temperatures, dm/dn was found to be strongly nonlinear already in weak magnetic fields, on a scale much smaller than the characteristic scales, expected for interacting two-dimensional electron gas. Surprisingly, this nonlinear behavior exists both in the dielectric, and in the metallic region. These observations, we believe, provide evidence for strong coupling of the itinerant and localized electrons in Si-MOSFET.

cond-mat.str-el↗

arXiv2009

Thermodynamic magnetization of a strongly interacting two-dimensional system

We report thermodynamic magnetization measurements of a 2-dimensional electron gas for several high mobility Si-MOSFETs. The low-temperature magnetization is shown to be strongly sub-linear function of the magnetic field. The susceptibility determined from the zero-field slope diverges as 1/T^α, with α=2.2-2.6 even at high electron densities, in apparent contradiction with the Fermi-liquid picture.

cond-mat.str-el↗

arXiv2009

Detection of non-Gaussian Fluctuations in a Quantum Point Contact

An experimental study of current fluctuations through a tunable transmission barrier, a quantum point contact, are reported. We measure the probability distribution function of transmitted charge with precision sufficient to extract the first three cumulants. To obtain the intrinsic quantities, corresponding to voltage-biased barrier, we employ a procedure that accounts for the response of the external circuit and the amplifier. The third cumulant, obtained with a high precision, is found to agree with the prediction for the statistics of transport in the non-Poissonian regime.

cond-mat.mes-hall↗

arXiv2005

Measurement of Counting Statistics of Electron Transport in a Tunnel Junction

We present measurements of the time-dependent fluctuations in electrical current in a voltage-biased tunnel junction. We were able to simultaneously extract the first three moments of the tunnel current counting statistics. Detailed comparison of the second and the third moment reveals that counting statistics is accurately described by the Poissonian distribution expected for spontaneous current fluctuations due to electron charge discreteness, realized in tunneling transport at negligible coupling to environment.

cond-mat.mes-hall↗

arXiv2004

Comment on "Critical behavior of the Pauli spin susceptibility..." by A. A. Shashkin et. al

The paper by A. A. Shashkin et al. [cond-mat/0409100] reports measurements of the thermodynamic magnetization of two-dimensional electrons in silicon. Although the experimental data is very similar to that reported by us more then two years ago, the authors arrive at an opposite conclusion regarding the spin susceptibility "critical behavior" and spin instability in the vicinity of the metal-insulator transition. We show that this interpretation is based on a flawed analysis of the experimental data.

cond-mat.str-el↗

arXiv2003

The thermodynamic spin magnetization of strongly correlated 2d electrons in a silicon inversion layer

A novel method invented to measure the minute thermodynamic spin magnetization of dilute two dimensional fermions is applied to electrons in a silicon inversion layer. Interplay between the ferromagnetic interaction and disorder enhances the low temperature susceptibility up to 7.5 folds compared with the Pauli susceptibility of non-interacting electrons. The magnetization peaks in the vicinity of the density where transition to strong localization takes place. At the same density, the susceptibility becomes extremely close to that of free spins (Curie susceptibility), indicating an almost perfect compensation of the kinetic energy toll associated with spin polarization by the energy gained from the ferromagnetic correlation. Yet, the balance favors a paramagnetic phase over spontaneous magnetization.

cond-mat.mes-hall↗

arXiv2001

Electron shot noise beyond the second moment

The form of electron counting statistics of the tunneling current noise in a generic many-body interacting electron system is obtained. The third correlator of current fluctuations (the skewness of the charge counting distribution) has a universal relation with the current I and the quasiparticle charge q. This relation C_3 = q^2 I holds in a wide bias voltage range, both at large and small eV/kT, thereby representing an advantage compared to the Schottky formula. We consider the possibility of using the counting statistics for detecting quasiparticle charge at high temperature.

cond-mat.mes-hall↗

arXiv2001

On the Cooling of Electrons in a Silicon Inversion Layer

The cooling of two-dimensional electrons in silicon-metal-oxide semiconductor field effect transistors is studied experimentally. Cooling to the lattice is found to be more effective than expected from the bulk electron-phonon coupling in silicon. Unexpectedly, the extracted heat transfer rate to phonons at low temperatures depends cubically on electron temperature, suggesting that piezoelectric coupling (absent in bulk silicon) dominates over deformation potential. According to our findings, at 100 mK, electrons farther than 0.1 mm from the contacts are mostly cooled by phonons. Using long devices and low excitation voltage we measure electron resistivity down to 100 mK and find that some of the "metallic" curves, reported earlier, turn insulating below about 300 mK. This finding renders the definition of the claimed 2D metal-insulator transition questionable. Previous low temperature measurements in silicon devices are analyzed and thumb rules for evaluating their electron temperatures are provided.

cond-mat.mes-hall↗

arXiv1999

Observation of a Fifth of the Electron Charge

We report the observation of quasi-particles with a charge q=e/5 detected by shot noise measurements in the 2/5 conducting channel (filling factor 2/5). This is in agreement with previous measurements that showed that the current in the lower, 1/3, channel is carried by quasiparticles with a charge q=e/3. These results demonstrate that the actual fraction of the charge can be different from the filling factor. Moreover, we show that there is no strong interaction between the channels, which can be considered as conducting the current independently.

cond-mat.mes-hall↗

arXiv1997

Direct Observation of a Fractional Charge

We performed measurements of Quantum Shot Noise in order to determine the quasiparticle charge in the Fractional Quantum Hall regime. The noise is generated by a current flow through a partially transmitting Quantum Point Contact in a 2DEG. The noise is directly proportional to the charge of the quasiparticles, thus allowing direct determination of the charge. We measured Quantum Shot Noise at a filling factor of 1/3 and found that the charge is e/3; as predicted by Laughlin.

cond-mat.mes-hall↗