arXiv subjects

A. Kononov

Publications and source records attributed to A. Kononov.

23 records · Page 2Linked to original sources

arXiv2015

Andreev reflection at the edge of a two-dimentional semimetal

We investigate electron transport through the interface between a niobium superconductor and the edge of a two-dimensional semimetal, realized in a 20~nm wide HgTe quantum well. Experimentally, we observe that typical behavior of a single Andreev contact is complicated by both a pronounced zero-bias resistance anomaly and shallow subgap resistance oscillations with $1/n$ periodicity. These results are demonstrated to be independent of the superconducting material and should be regarded as specific to a 2D semimetal in a proximity with a superconductor. We interpret these effects to originate from the Andreev-like correlated process at the edge of a two-dimensional semimetal.

cond-mat.mes-hall↗

arXiv2015

Evidence on the macroscopic length scale spin coherence for the edge currents in a narrow HgTe quantum well

We experimentally investigate spin-polarized electron transport between two ferromagnetic contacts, placed at the edge of a two-dimensional electron system with band inversion. The system is realized in a narrow (8~nm) HgTe quantum well, the ferromagnetic side contacts are formed from a pre-magnetized permalloy film. In zero magnetic field, we find a significant edge current contribution to the transport between two ferromagnetic contacts. We experimentally demonstrate that this transport is sensitive to the mutual orientation of the magnetization directions of two 200~$μ$m-spaced ferromagnetic leads. This is a direct experimental evidence on the spin-coherent edge transport over the macroscopic distances. Thus, the spin is extremely robust at the edge of a two-dimensional electron system with band inversion, confirming the helical spin-resolved nature of edge currents.

cond-mat.mes-hall↗

arXiv2015

Conductance oscillations at the interface between a superconductor and the helical edge channel in a narrow HgTe quantum well

We experimentally investigate electron transport through the interface between a superconductor and the edge of a two-dimensional electron system with band inversion. The interface is realized as a tunnel NbN side contact to a narrow 8~nm HgTe quantum well. It demonstrates a typical Andreev behavior with finite conductance within the superconducting gap. Surprisingly, the conductance is modulated by a number of equally-spaced oscillations. The oscillations are present only within the superconducting gap and at lowest, below 1~K, temperatures. The oscillations disappear completely in magnetic fields, normal to the two-dimensional electron system plane. In contrast, the oscillations' period is only weakly affected by the highest, up to 14~T, in-plane oriented magnetic fields. We interpret this behavior as the interference oscillations in a helical one-dimensional edge channel due to a proximity with a superconductor.

cond-mat.mes-hall↗

arXiv2014

Current-induced magnetization dynamics at the edge of a two-dimensional electron system with strong spin-orbit coupling

We experimentally investigate electron transport through the interface between a permalloy ferromagnet and the edge of a two-dimensional electron system with strong Rashba-type spin-orbit coupling. We observe strongly non-linear transport around zero bias at millikelvin temperatures. The observed nonlinearity is fully suppressed above some critical values of temperature, magnetic field, and current through the interface. We interpret this behavior as the result of spin accumulation at the interface and its current-induced absorption as a magnetization torque.

cond-mat.mes-hall↗

arXiv2012

Energy spectrum reconstruction at the edge of a two-dimensional electron system with strong spin-orbit coupling

We experimentally demonstrate the simultaneous reconstruction of the bulk and the edge energy spectra caused by strong spin-orbit interaction, at the two lowest filling factors $ν=1$ and $ν=2$ for $In_xGa_{1-x}As$ two-dimensional electron system with $x = 0.75$. The observed reconstruction is of different character at these filling factors: it is characterized by zeroing of the energy gap at the levels crossing point at $ν=2$, while the reconstruction at $ν=1$ goes through the coexistence of two $ν=1$ quantum Hall phases with different spin projections. An analysis indicates a strong influence of many-body interaction on the reconstruction at $ν=1$.

cond-mat.mes-hall↗