arXiv subjects

I. A. Cohn

Publications and source records attributed to I. A. Cohn.

6 recordsLinked to original sources

arXiv2025

Strain-induced proximity effect in topological insulator TaSe$_3$

The magnetoresistance of superconductor-topological insulator-superconductor structures, with indium as the superconductor and TaSe$_3$ as the topological insulator, shows steplike features on the resistance under magnetic fields. These resistance steps are resulted from the suppression of superconductivity, induced by the superconducting proximity effect in both the bulk and surface states of the topological insulator. The position and amplitude of the steps, occurring at approximately 0.1 T, show an unusual dependence on the magnitude of the uniaxial strain ($ε$), indicating their connection with surface states. This behavior follows the expected transition sequence: semi-metal $\rightarrow$ strong topological insulator $\rightarrow$ trivial insulator, and supports the presence of surface states at $0.46\% \lesssim ε\lesssim 0.85\%$.

cond-mat.supr-con↗

arXiv2025

Slow Oscillations of the Transverse Magnetoresistance in HoTe3

Slow oscillations of the magnetoresistance periodic in the inverse magnetic field with a frequency of 3.4 T have been identified in HoTe3. The temperature dependence of the oscillation amplitude is close to exponential even at low temperatures. This may be attributed to the existence of soft modes in the system and allows the estimation of the electron scattering rate on these modes. In the region of magnetic fields exceeding 1 T, the oscillations can be described as interference oscillations associated with the splitting of the band structure due to the bilayer structure of HoTe3. The obtained data have allowed us to calculate the ratio tb/tz~7.7 of the hopping integrals between layers within each bilayer (tb) and between the adjacent bilayers (tz) to estimate these integrals as tb ~ 2 meV and tz ~ 0.26 meV.

cond-mat.str-el↗

arXiv2024

Superconductivity in thin films of RuN

Superconductivity has been found in RuN films obtained by reactive magnetron sputtering. This is a novel member of the metal nitride superconductors family. The critical temperature of the superconducting transition varies depending on the substrate and ranges from 0.77 K to 1.29 K. The parameters of the crystal lattice of superconducting films have been determined: the lattice is distorted cubic with parameters $a = b = c = 4.5586$ Å, $α=β=γ=87.96^\circ$. A zero temperature upper critical magnetic field $H_{c2}(0)$ and the coherence length were found from the experimental data using WHH model. $H_{c2}(0) = 2.3$ T- 4.1 T for different substrates and exceeds the upper paramagnetic limit, as well as $ξ= 12$ nm. An s-wave single band energy gap $Δ(0) = 0.19$ meV was revealed by self-field critical current experiment at temperatures down to 10 mK, $2Δ/kT_c =5.5$ exceeding the BCS ratio 3.5.

cond-mat.supr-con↗

arXiv2023

Activated and quantum creep of the charge-density waves in magnetic field in {\it o}-TaS$_3$

We demonstrate that magnetoresistance of creeping charge-density waves in the quasi-one dimensional conductor {\it o}-TaS$_3$ changes its character from a negative parabolic at $T\gtrsim 10$ K where it obeys $1/T^2$ law to a weakly temperature dependent negative nearly linear one at lower temperatures. The dominant contribution into the negative parabolic magnetoresistance comes from magnetic field induced splitting of the CDW order parameter. The linear magnetoresistance arises due to CDW quantum interference similar to the scenario of negative linear magnetoresistance in single-electron systems.

cond-mat.mtrl-sci↗

arXiv2020

Magnetoresistance in quasi-one dimensional Weyl semimetal (TaSe$_4$)$_2$I

Magnetic field effect on linear and nonlinear conductivity in a quasi-one-dimensional Weyl semimetal with a charge density wave (CDW) (TaSe$_4$)$_2$I is studied. Longitudinal magnetoresistance in all known regimes of CDW motion (linear conduction, creep, sliding, "Fröhlich superconductivity") is small, positive and do not exceed a fraction of per cent. Similar magnetotransport measurements were performed in samples profiled by focused ion beams is such a way that motion of the CDW in them is accompanied by phase slip of the CDW. In such samples, a peak-like non-parabolic negative magnetoresistance is observed in relatively small magnetic fields $B \lesssim 4$ T in the nonlinear conduction regime in both longitudinal and transverse geometries. Our results differ significantly from ones obtained earlier and raise the question concerning conditions for observing the axion anomaly in Weyl semimetals in the Peierls state.

cond-mat.mtrl-sci↗

arXiv2019

Non-quadratic transverse magnetoresistance of the nodal line Dirac semimetal InBi

The transverse magnetoresistance of a nodal line Dirac semi-metal InBi has been studied. It is found that the magnetoresistance is not quadratic. In the region of small magnetic fields $ B\lesssim 0.1$~T, it is characterized by high curvature, in the region of medium magnetic fields it is described by the sum of linear and quadratic contributions, and in the region of large magnetic fields $ B\gtrsim 1$~T, it approaches a quadratic law with a curvature several times smaller its zero field value. A phenomenological equation is proposed that allows to describe the entire dependence of the resistance on the magnetic field with an error not exceeding the measurement error of several percent.

cond-mat.mtrl-sci↗