Serhii Shafranjuk

Carbon nanotube quantum dots as highly sensitive terahertz-cooled spectrometers.

Terahertz technology has recently emerged as a highly sought-after and versatile scientific tool in many fields, including medical imaging, security screening, and wireless communication. However, scientific progress has been hindered by the lack of sources and detectors in this frequency range, thereby known as the terahertz gap. Here, we show that carbon nanotube quantum dots coupled to antennas are extremely sensitive, broad-band, terahertz quantum detectors with spectral resolution. Their response is due to photon-assisted single-electron tunneling and it is substantially enhanced by a novel radiation-induced nonequilibrium cooling of the electrons, causing a sharp height increase of the Coulomb oscillation peaks.

Electronic transport and possible superconductivity at van Hove singularities in carbon nanotubes

Van Hove singularities (VHSs) are a hallmark of reduced dimensionality, leading to a divergent density of states in one and two dimensions and predictions of new electronic properties when the Fermi energy is close to these divergences. In carbon nanotubes, VHSs mark the onset of new subbands. They are elusive in standard electronic transport characterization measurements because they do not typically appear as notable features and therefore their effect on the nanotube conductance is largely unexplored. Here we report conductance measurements of carbon nanotubes where VHSs are clearly revealed by interference patterns of the electronic wave functions, showing both a sharp increase of quantum capacitance, and a sharp reduction of energy level spacing, consistent with an upsurge of density of states. At VHSs, we also measure an anomalous increase of conductance below a temperature of about 30 K. We argue that this transport feature is consistent with the formation of Cooper pairs in the nanotube.

A qubit device based on manipulations of Andreev bound states in double-barrier josephson junctions

Abstract A qubit system exploiting manipulations of the Andreev bound state (ABS) levels in the SINIS junction by applying appropriate bias voltages and transport currents is suggested. The parameters of the SINIS setup may be chosen in such a way that only two ABS levels are present; this is in agreement with our experimental data obtained using Nb/Al double-barrier junctions. In the qubit Hamiltonian, H , the two ABS levels are presented as the ‘↑’ and ‘↓’ spin states, while the controlling physical parameters (voltage across one of the barriers and the transport current) are mapped to the ‘magnetic fields’ B x n and B z n . The phase decoherence time is estimated.

Probing the intrinsic state of a one-dimensional quantum well with photon-assisted tunneling

The photon-assisted tunneling (PAT) through a single wall carbon nanotube quantum well (QW) under influence an external electromagnetic field for probing of the Tomonaga Luttinger liquid (TLL) state is suggested. The elementary TLL excitations inside the quantum well are density (

Current-voltage characteristics of Nb-carbon-Nb junctions

\rho_{\pm}

Optimization of the double-barrier Josephson junction switching dynamics

) and spin (

Principles of Josephson-Junction-Based Quantum Computation

\sigma_{\pm}

A particle detector based on a double barrier Josephson junction

) bosons. The bosons populate the quantized energy levels

Carbon nanotubes as nanoscale probes of the superconducting proximity effect in Pd-Nb junctions

\epsilon^{\rho +}_n =\Delta n/ g

The search for superconductivity at van Hove singularities in carbon nanotubes

and