A5079166408- Quantum and electron transport phenomena
- Physics of Superconductivity and Magnetism
- Quantum Information and Cryptography
- Quantum Computing Algorithms and Architecture
- Molecular Junctions and Nanostructures
- Advanced Condensed Matter Physics
- Topological Materials and Phenomena
- Surface and Thin Film Phenomena
- Semiconductor Quantum Structures and Devices
- Advancements in Semiconductor Devices and Circuit Design
- Quantum Mechanics and Applications
- Magnetic properties of thin films
- Quantum Mechanics and Non-Hermitian Physics
- Theoretical and Computational Physics
- Mechanical and Optical Resonators
- Graphene research and applications
- Terahertz technology and applications
- Organic and Molecular Conductors Research
- Atomic and Subatomic Physics Research
- Quantum, superfluid, helium dynamics
- Force Microscopy Techniques and Applications
- Quantum many-body systems
- Magnetic and transport properties of perovskites and related materials
- High-pressure geophysics and materials
- Cold Atom Physics and Bose-Einstein Condensates
University of Ljubljana
2015-2025
Jožef Stefan Institute
2014-2025
University of Helsinki
2020
Institute of Mathematics, Physics, and Mechanics
2001-2003
Max Planck Society
1992-1998
Max Planck Institute for Solid State Research
1992-1994
Around forty years have passed since the first pioneering works introduced possibility of using quantum physics to strongly enhance communications safety. Nowadays Quantum Cryptography, and in particular, Key Distribution (QKD) exited laboratories become commercial technologies that increasingly trigger attention States, military forces, banks, private corporations. This work takes on challenge bringing QKD closer a consumer technology: optical fibers deployed used by telecommunication...
Using analytical arguments and the numerical renormalization group method, we investigate spin thermopower of a quantum dot in magnetic field. In particle-hole-symmetric situation, temperature difference applied across drives pure current without accompanying charge current. For temperatures fields at or above Kondo temperature, but same order magnitude, spin-Seebeck coefficient is large, ${k}_{B}/|e|$. Via mapping, relate to charge-Seebeck negative-$U$ where corresponding result was...
We explore anomalous high-harmonic generation in a model that realizes transition from broken time-reversal symmetry Weyl-semimetal to semi-Dirac regime, i.e. gapless semimetal with dispersion is parabolic one direction and conical the other two. point out intensity of induced high harmonics regime. For Weyl semimetals, we reveal are due excitations at momenta where not strictly linear linearized low-energy theory response harmonic only. Our findings aid experimental characterization Weyl,...
We study a two-terminal Josephson junction with conventional superconductors and normal region Rashba spin-orbit interaction, characterized by two Aharonov-Casher (AC) fluxes. When the superconducting phase difference equals <a:math xmlns:a="http://www.w3.org/1998/Math/MathML"><a:mi>π</a:mi></a:math>, Andreev subgap spectrum may host zero-energy Weyl singularities associated vanishing normal-state reflection eigenvalue. With one of AC fluxes playing role quasimomentum, can be viewed as an...
Numerical analysis of the simplest odd-numbered system coupled quantum dots reveals an interplay between magnetic ordering, charge fluctuations, and tendency itinerant electrons in leads to screen moments. The transition from local-moment molecular-orbital behavior is visible evolution correlation functions as interdot coupling increased. Resulting Kondo phases are presented a phase diagram which can be sampled by measuring zero-bias conductance. We discuss origin even-odd effects comparing...
Thermoelectric transport coefficients are determined for semiconductor quantum wires with weak thickness fluctuations. Such systems exhibit anomalies in conductance near 1/4 and 3/4 of 2e^2/h on the rising edge to first plateau, explained by singlet triplet resonances conducting electrons a single weakly bound electron wire [T. Rejec, A. Ramsak, J.H. Jefferson, Phys. Rev. B 62, 12985 (2000)]. We extend this work study Seebeck thermopower coefficient linear thermal within framework...
The change of the spectral properties single-particle Green's function due to a coupling optical phonons is investigated for strongly correlated electrons. phonon-induced mass renormalization carriers that propagate in t-J model on scale J much larger than corresponding uncorrelated model, except limit J\ensuremath{\rightarrow}0 where weight quasiparticle pole tends zero. enhancement consequence slow coherent motion spin polarons, which makes electron-phonon interactions more effective. Two...
We investigate a symmetrical double quantum dot system serially attached to the leads. The emphasis is on numerical analysis of finite interdot tunneling in presence repulsive capacitive coupling. results reveal competition between extended Kondo phases and local singlet spin charge degrees freedom. corresponding phase diagram determined quantitatively.
The self-consistent Born approximation for the self-energy and wave function of a single hole moving in two-dimensional quantum antiferromagnet is used to calculate various spin-correlation functions that characterize perturbation induced by hole. results these correlation agree with available small-cluster calculations. hole-spin decay asymptotically distance from as power law exhibit dipolar distortion antiferromagnet. quasiparticle spectral weight remains finite.
An exact analytical solution is derived for the wave function of an electron in a one-dimensional moving quantum dot nanowire, presence time-dependent spin-orbit coupling. For cyclic evolutions we show that spin rotated by angle proportional to area closed loop parameter space position and amplitude fictitious classical oscillator driven By appropriate choice parameters, may be arbitrary on Bloch sphere. Exact expressions dynamical geometrical phases are also derived.
The conductance through a quantum wire of cylindrical cross section and weak bulge is solved exactly for two electrons within the Landauer-Buettiker formalism. We show that this 'open' dot exhibits spin-dependent Coulomb blockade resonances resulting in anomalous structure on rising edge to first plateau, one near 0.25(2e^2/h), related singlet resonance, 0.7(2e^2/h), triplet resonance. These are generic robust, occurring other types surviving temperatures few degrees.
Entanglement can be generated by two electrons in a spin-zero state on semiconducting single-walled carbon nanotube. The electrons, one weakly bound shallow well the conduction band, and other injected into are coupled Coulomb interaction. Both transmission entanglement dependent characteristics, which controlled local gate, kinetic energy of electron. Regimes with different degrees electron correlation exhibit full or partial entanglement. In latter case, maximum estimated as function width...
The deformation of the quantum N\'eel state induced by a spin polaron is analyzed in slave fermion approach. Our method based on self-consistent Born approximation for Green's function and wave quasiparticle. results various spin-correlation functions relative to position moving hole are discussed shown agree with those available from small cluster calculations. Antiferromagnetic correlations direct neighborhood reduced, but they remain antiferromagnetic even $J$ as $0.1t$. These correlation...
Zero temperature linear response conductance of molecules with Coulomb interaction and various types phonon modes is analyzed together local occupation, moment, charge fluctuations. Particular emphasis on deformation fluctuations, which are quantitatively related to Charge fluctuations shown exhibit similarity static susceptibility.
We investigate the competition between pair entanglement of two spin qubits in double quantum dots attached to leads with various topologies and separate each nearby electrodes. Universal behavior is demonstrated dependence on mutual interactions qubits, coupling their environment, temperature, magnetic field. As a consequence phase transition an abrupt switch fully entangled unentangled states takes place when are coupled parallel.
We investigate the electrical conductance and thermopower of a quantum dot tunnel coupled to external leads described by an extension Anderson impurity model which takes into account assisted hopping processes, i.e., occupancy-dependence tunneling amplitudes. provide analytical understanding based on scaling arguments Schrieffer–Wolff transformation, corroborated detailed numerical calculations using renormalization group method. The modifies coupling two-particle state, shifts Kondo...
We study the topological properties and transport in Bernevig-Hughes-Zhang model undergoing a slow quench between different regimes. Due to closing of band gap during quench, system ends up an excited state. prove that for quenches preserve time-reversal symmetry, ${\mathbb{Z}}_{2}$ invariant remains equal one evaluated initial On other hand, bulk spin Hall conductivity does change, its time average approaches ground state final Hamiltonian. The deviations from ground-state as function...
An exact solution is derived for the wavefunction of an electron in a semiconductor quantum wire with spin–orbit interaction and driven by external time-dependent harmonic confining potential. The formalism allows analytical expressions various quantities to be derived, example spin pseudo-spin rotations, energy occupation probabilities excited states. It demonstrated how perfect flips can achieved at high frequencies order ω, potential level spacing. By appropriately chosen driving term,...
We consider a triple quantum dot system in triangular geometry with one of the dots connected to metallic leads. Using Wilson's numerical renormalization group method, we investigate entanglement and its relation thermodynamic transport properties, regime where each is singly occupied on average, but non-negligible charge fluctuations. It shown that even significant fluctuations formation Kondo singlets induces switching between separable perfectly entangled states. The phase transition...
The zero-temperature linear response conductance through an interacting mesoscopic region attached to noninteracting leads is investigated. We present a set of formulas expressing the in terms persistent currents auxiliary system, namely ring threaded by magnetic flux and containing correlated electron region. first derive for case then give arguments why formalism also correct if ground state system exhibits Fermi liquid properties. prove that such systems, ground-state energy universal...
Spectral functions within the generalized $t\ensuremath{-}J$ model as relevant to cuprates are analyzed using method of equations motion for projected fermion operators. In evaluation self-energy a decoupling spin and single-particle fluctuations is performed. It shown that in an undoped antiferromagnet reproduces self-consistent Born approximation. For finite doping with short-range antiferromagnetic order approximation evolves into paramagnon contribution which retains large incoherent...
A theory of superconductivity within the extended $t\text{\ensuremath{-}}J$ model, as relevant for cuprates, is developed. It based on equations motion projected fermionic operators and mode-coupling approximation self-energy matrix. The dynamical spin susceptibility at various doping considered an input, extracted from experiments. analysis shows that onset dominated by spin-fluctuation contribution. coupling to fluctuations directly involves next-nearest-neighbor hopping...
A weakly bound electron in a semiconductor quantum wire is shown to become entangled with an itinerant via the Coulomb interaction. The degree of entanglement and its variation energy injected electron, may be tuned by choice spin initial momentum. Full achieved close energies where there are spin-dependent resonances. Possible realisations related device structures discussed.
We investigate the electronic transport through a molecule in Kondo regime. The tunneling between electrode and is asymmetrically modulated by oscillations of molecule, i.e., if gets closer to one electrodes that will increase while for other it decrease. system described two-channel Anderson model with phonon-assisted hybridization, which solved Wilson numerical renormalization group method. results several functional forms modulation are presented. For linearized screening molecular spin...