Searcharxiv⌕ Search

arXiv subjects

Can Yesilyurt

Publications and source records attributed to Can Yesilyurt.

At least 19 recordsLinked to original sources
arXiv2026

Asymmetric optical transmission from broken interface-orientation symmetry in self-shadowed grating metallizations

Reciprocal optical structures can transmit finite-angle illumination asymmetrically when the two illumination directions couple differently to the available diffraction channels. We realize this in a single overlay-free step: oblique metallization of a conventional diffraction grating, where ballistic self-shadowing grows a one-sided, louver-like silver profile. Electron microscopy and Ag mapping show the one-sided silver redistribution on oblique-coated films and its absence on a normal-incidence control. Full-wave Maxwell calculations on the ballistic-growth geometry predict broadband substrate-favored transmission, carried by the transverse-magnetic (TM) polarization in the diffraction regime (contrast up to 2.1) and polarization-independent and spectrally flat (1.5-1.9) deep in the geometric regime; the rejected power is redirected predominantly into specular reflection, and the deposition angle selects the magnitude and sign of the effect (optimum near $45^\circ$). Calibrated three-color sample-reversal measurements yield dark-corrected substrate-favored ratios that persist in both output-analyzer projections on a $45^\circ$-coated 1-$\mu$m-period film (up to 1.8) and lie within the computed geometric-regime band on a 30-$\mu$m-period film (1.5-1.8, with reference-normalized absolute transmittances).

physics.optics↗
arXiv2026

Coherent Nonreciprocal Valley Transport in Dirac/Weyl Semimetals

Nonreciprocal electronic transport, characterized by directional asymmetry between forward and backward two-terminal responses, typically requires an intrinsic inversion-breaking feature in the host material or an applied field, such as magnetic order, magnetochiral coupling, polar lattice distortion, or a superconducting state. This study demonstrates that a single electrostatic barrier with a shape lacking inversion symmetry can induce coherent nonreciprocal transport in a Dirac or Weyl channel without these conventional requirements. The underlying mechanism is geometric: when a barrier possesses two qualitatively distinct refraction interfaces, specifically one vertical and one oblique, forward- and backward-propagating wave packets encounter different Fermi-surface-mismatch sequences at the entrance and exit faces. Coherent split-operator Dirac wave-packet simulations with realistic device parameters reveal that, in a channel with isotropic (untilted) energy dispersion, an inversion-asymmetric (right-angle) triangular barrier produces pronounced charge-mode rectification, confirming its geometric origin. Introducing a Dirac-cone tilt causes the same barrier shape to exhibit coherent, valley-resolved one-way transport, with the dichroic structure reversing sign across the Dirac point. Notably, a mirror-symmetric (isosceles) triangle with two oblique faces yields valley-polarized transmission while remaining exactly reciprocal. The combination of oblique interfaces and tilt alone is insufficient; the essential factor is the presence of a sequence of geometrically distinct interface types.

cond-mat.mes-hall↗
arXiv2026

Electrostatic control of valley-dependent phase in tilted Dirac/Weyl channels

Valley degrees of freedom represent a promising resource for solid-state quantum information. This work demonstrates electrostatic control of the valley-dependent phase in tilted Dirac/Weyl semimetals. When wave packets traverse a shaped electrostatic barrier, the valley-dependent tilt induces differential spatial drift and dwell times, resulting in the accumulation of a continuously tunable relative dynamical phase. The barrier thereby functions as a valley-phase shift element. Time-dependent transport simulations employing a coupled two-valley model yield electrically tunable relative phases between equal-energy valleys, including $\pi/4$, $\pi/2$, and $\pi$, with high transmission probabilities.

cond-mat.mes-hall↗
arXiv2026

Parabolic-Cylinder Approach to Valley-Polarized Conductance in Tilted Anisotropic Dirac-Weyl Systems

We develop a parabolic-cylinder approach to valley-polarized conductance in tilted anisotropic Dirac-Weyl systems, showing that the smooth-interface scattering problem can be reduced analytically to the Weber equation, which belongs to the same differential-equation class as the quantum harmonic oscillator. This reduction yields closed-form expressions for the angular transmission envelope and clarifies the distinct roles of the tilt components: the perpendicular tilt renormalizes the tunneling-envelope width, while the parallel tilt shifts the Fabry-Perot resonance structure differently in opposite valleys. Combined with the nonlinear mapping between the fixed device frame and the rotated barrier frame, this analytical structure provides a direct route from valley-dependent interface tunneling to net valley-polarized conductance. We apply the formalism to rotated electrostatic barriers and construct phase diagrams over barrier angle, tilt strength, width, height, and Fermi energy. The results reveal a robust optimum near t = 0.2 over the parameter range studied, identify the crossover from oscillatory to monotonic polarization regimes, and delineate practical operating windows for candidate materials including 8-Pmmn borophene and WTe2.

cond-mat.mes-hall↗
arXiv2026

All-Electrostatic Valley Filtering by Barrier Rotation in Tilted Dirac/Weyl Semimetals

Charge carriers in Dirac/Weyl semimetals with tilted anisotropic energy dispersion exhibit valley-dependent refraction and reflection at electrostatic barrier interfaces. Here, we show that an angled barrier interface provides a purely electrostatic route to valley filtering, producing finite valley-polarized conductance. We develop a generalized transfer-matrix formalism for the tilted, anisotropic Dirac Hamiltonian, extend it to treat electrostatic barriers at arbitrary angles, and calculate the transmission in the rotated-barrier frame. We also present simulated valley-resolved trajectories in a finite device geometry, demonstrating that one valley is selectively transmitted, while the other is predominantly reflected by the angled barrier, without invoking real or pseudomagnetic fields.

cond-mat.mes-hall↗
arXiv2021

Dzyaloshinskii-Moriya interaction as a fast quantum information scrambler

Black holes are conjectured to be the fastest information scramblers, and within holographic duality, the speed of quantum information scrambling of thermal states of quantum systems is at the heart of studies of chaos and black hole dynamics. Here, considering the Ising interaction on the thermal state of spin chains with Dzyaloshinskii-Moriya (DM) interaction and measuring the out-of-time-order correlation functions, we study the effect of DM interaction on the speed of scrambling the quantum information. On the contrary to its advantages in quantum information and metrology such as exciting entanglement and quantum Fisher information, we show that DM interaction speeds up the information scrambling. We also show that the increasing temperature slows down the scrambling process due to vanishing quantum correlations.

quant-ph↗
arXiv2021

Deterministic preparation of W states via spin-photon interactions

Spin systems such as silicon or nitrogen vacancy centers in diamond, quantum dots and quantum dot molecules coupled to optical cavities appear as key elements for creating quantum networks as not only constituting the nodes of the network, but also assisting the creation of photonic networks. Here we study deterministic preparation of arbitrary size $W$ states with spin systems. We present an efficient operation on three qubits, two being the logical qubits and one being the ancillary qubit, where no interaction between the logical qubits are required. The proposed operation can create a $W$-type Einstein-Podolsky-Rosen (EPR) pair from two separable qubits, and expand that EPR pair or an arbitrary size $W$ state by one, creating a $W$-like state. Taking this operation as the fundamental building block, we show how to create a large scale $W$ state out of separable qubits, or double the size of a $W$ state. Based on this operation and focusing on nitrogen vacancy (NV) centers in diamond as an exemplary spin system, we propose a setup for preparing $W$ states of circularly polarized photons, assisted by a single spin qubit, where no photon-photon interactions are required. Next, we propose a setup for preparing $W$ states of spin qubits of spatially separated systems, assisted by a single photon. We also analyze the effects of possible imperfections in implementing the gates on the fidelity of the generated $W$ states. In our setups, neither post-measurement, nor post-processing on the states of spin or photonic qubit is required. Our setups can be implemented with current technology, and we anticipate that they contribute to quantum science and technologies.

quant-ph↗
arXiv2018

Quantum dots formed in three-dimensional Dirac semimetal Cd$_3$As$_2$ nanowires

We demonstrate quantum dot (QD) formation in three-dimensional Dirac semimetal Cd$_{3}$As$_{2}$ nanowires using two electrostatically tuned p$-$n junctions with a gate and magnetic fields. The linear conductance measured as a function of gate voltage under high magnetic fields is strongly suppressed at the Dirac point close to zero conductance, showing strong conductance oscillations. Remarkably, in this regime, the Cd$_{3}$As$_{2}$ nanowire device exhibits Coulomb diamond features, indicating that a clean single QD forms in the Dirac semimetal nanowire. Our results show that a p$-$type QD can be formed between two n$-$type leads underneath metal contacts in the nanowire by applying gate voltages under strong magnetic fields. Analysis of the quantum confinement in the gapless band structure confirms that p$-$n junctions formed between the p$-$type QD and two neighboring n$-$type leads under high magnetic fields behave as resistive tunnel barriers due to cyclotron motion, resulting in the suppression of Klein tunneling. The p$-$type QD with magnetic field-induced confinement shows a single hole filling. Our results will open up a route to quantum devices such as QDs or quantum point contacts based on Dirac and Weyl semimetals.

cond-mat.mes-hall↗
arXiv2017

Anomalous tunneling characteristic of Weyl semimetals with tilted energy dispersion

Weyl semimetal is a recently discovered state of quantum matter, which generally possesses tilted energy dispersion. Here, we investigate the electron tunneling through a Weyl semimetal p-n-p junction. The angular dependence of electron tunneling exhibits an anomalous profile such that perfect transmission angles are shifted along the direction of the tilt. Coupling of the tilted dispersion and electrical potential within the barrier region gives rise to a transverse momentum shift, which is analogous to the transverse Lorentz displacement induced by magnetic barriers.

cond-mat.mes-hall↗
arXiv2017

Electrically tunable valley polarization in Weyl semimetals with tilted energy dispersion

Tunneling transport across the p-n-p junction of Weyl semimetal with tilted energy dispersion is investigated. We report that the electrons around different valleys experience opposite direction refractions at the barrier interface when the energy dispersion is tilted along one of the transverse directions. Chirality dependent refractions at the barrier interface polarize the Weyl fermions in angle-space according to their valley index. A real magnetic barrier configuration is used to select allowed transmission angles, which results in electrically controllable and switchable valley polarization. Our findings may pave the way for experimental investigation of valley polarization, as well as valleytronic and electron optic applications in Weyl semimetals.

cond-mat.mes-hall↗
arXiv2017

Deterministic generation of a four-qubit W state using one- and two-qubit gates

We propose an optical scheme to build an entangled network composed of W state based on polarization encoded qubits (photons). This new setup consists of 2 cNOT gates, 4 V gates, 2 Hadamard gates and basic optical tools such as polarizing beamsplitters (PBSs) and path couplers (PCs). V gate is a specially-designed tool acting as a two-qubit gate which is composed of a cNOT gate, 3 PBSs and a PC. By using this gate, one benefits from the temporarily generated optical degree of freedom, which is the spatial mode of a photon in the proposed scheme. Using an extra degree of freedom allows us to perform more capable processing for W-state creation protocols. We use four photons as input, which means we do not need entanglement as a resource. Also, we show that the proposed scheme can be implemented by operating the quantum optical gates which can be realized via current photonics technology. Additionally, we provide discussions of quantum contextuality and non-locality for W states.

quant-ph↗
arXiv2017

Conductance modulation in Weyl semimetals with tilted energy dispersion without a band gap

We investigate the tunneling conductance of Weyl semimetal with tilted energy dispersion by considering electron transmission through a p-n-p junction with one-dimensional electric and magnetic barrier. In the presence of both electric and magnetic barriers, we found that a large conductance gap can be produced by the aid of tilted energy dispersion without a band gap. The origin of this effect is the shift of the electrons wave-vector at barrier boundaries caused by i) the pseudo-magnetic field induced by electrical potential, i.e., a newly discovered feature that is only possible in the materials possessing tilted energy dispersion, ii) the real magnetic field induced by ferromagnetic layer deposited on the top of the system. We use realistic barrier structure applicable in current nanotechnology and analyze the temperature dependence of the tunneling conductance. The new approach presented here may resolve a major problem of possible transistor applications in topological semimetals, i.e., the absence of normal backscattering and gapless band structure.

cond-mat.mes-hall↗
arXiv2016

Influence of Fermi arc states and double Weyl node on tunneling in a Dirac semimetal

Most theoretical studies of tunneling in Dirac and the closely related Weyl semimetals have modeled these materials as single Weyl nodes described by the three-dimensional Dirac equation $H = v_f \vec{p}\cdot\vecσ$. The influence of scattering between the different valleys centered around different Weyl nodes, and the Fermi arc states which connect these nodes are hence not evident from these studies. In this work we study the tunneling in a thin film system of the Dirac semimetal $\text{Na}_3\text{Bi}$ consisting of a central segment with a gate potential, sandwiched between identical semi-infinite source and drain segments. The model Hamiltonian we use for $\text{Na}_3\text{Bi}$ gives, for each spin, two Weyl nodes separated in $k$-space symmetrically about $k_z=0$. The presence of a top and bottom surface in the thin film geometry results in the appearance of Fermi arc states and energy subbands. We show that (for each spin) the presence of two Weyl nodes and the Fermi arc states result in enhanced transmission oscillations, and finite transmission even when the energy falls within the \textit{bulk} band gap in the central segment respectively. These features are not evident in single Weyl node models.

cond-mat.mes-hall↗
arXiv2016

Klein tunneling in Weyl semimetals under the influence of magnetic field

Klein tunneling refers to the absence of normal backscattering of electrons even under the case of high potential barriers. At the barrier interface, the perfect matching of electron and hole wavefunctions enables a unit transmission probability for normally incident electrons. It is theoretically and experimentally well understood in two-dimensional relativistic materials such as graphene. Here we investigate the Klein tunneling effect in Weyl semimetals under the influence of magnetic field induced by anti-symmetric ferromagnetic stripes placed at barrier boundaries. Our results show that the resonance of Fermi wave vector at specific barrier lengths gives rise to perfect transmission rings, i.e., three-dimensional analogue of the so-called magic transmission angles in two-dimensional Dirac semimetals. Besides, the transmission profile can be shifted by application of magnetic field, a property which may be utilized in electro-optic applications. When the applied potential is close to the Fermi level, a particular incident vector can be selected for transmission by tuning the applied magnetic field, thus enabling highly selective transmission of electrons in the bulk of Weyl semimetals. Our analytical and numerical calculations obtained by considering Dirac electrons in three regions and using experimentally feasible parameters can pave the way for relativistic tunneling applications in Weyl semimetals.

cond-mat.mes-hall↗
arXiv2016

Deterministic Local Expansion of W States

In large quantum systems multipartite entanglement can be found in many inequivalent classes under local operations and classical communication. Preparing states of arbitrary size in different classes is important for performing a wide range of quantum protocols. W states, in particular, constitute a class with a variety of quantum networking protocols. However, all known schemes for preparing W states are probabilistic, with resource requirements increasing at least sub-exponentially. We propose a deterministic scheme for preparing W states that requires no prior entanglement and can be performed locally. We introduce an all-optical setup that can efficiently prepare W states of arbitrary size. Our scheme advances the use of W states in real-world quantum networks and could be extended to other physical systems.

quant-ph↗
arXiv2016

Perfect valley filter in strained graphene with single barrier region

We present a single barrier system to generate pure valley-polarized current in monolayer graphene. A uniaxial strain is applied within the barrier region, which is delineated by localized magnetic field created by ferromagnetic stripes at the regions boundaries. We show that under the condition of matching magnetic field strength, strain potential, and Fermi energy, the transmitted current is composed of only one valley contribution. The desired valley current can transmit with zero reflection while the electrons from the other valley are totally reflected. Thus, the system generates pure valley-polarized current with maximum conductance. The chosen parameters of uniaxial strain and magnetic field are in the range of experimental feasibility, which suggests that the proposed scheme can be realized with current technology.

cond-mat.mes-hall↗
arXiv2016

Efficient Dual Spin-Valley Filter In Strained Silicene

We propose a highly efficient silicene device for dual spin and valley filtering. The device consists of two different barrier regions: the first is a region under uniaxial strain, with an exchange field induced by adjacent top and bottom magnetic insulators, while the second comprises of two ferromagnetic stripes which produces a delta-function fringe magnetic field, and a gate electrode to modify the electrochemical potential. For the first region, we investigated the effect of the uniaxial strain in inducing angular separation of the two valley spins in momentum-space, and further spin separation by the spin dependent electric potential induced by the exchange field. We then evaluated the delta-function magnetic field and electrochemical potential combination in the second region to yield the transverse displacement for the selection of the requisite spin-valley combination. We demonstrated the optimal conditions in the first barrier to induce a highly anisotropic transmission profile, which enables controllable and efficient filtering (> 90% efficiency) by the second region for all four spin-valley combinations. Based on the analytical results, we predict the feasibility of experimental realization of dual spin-valley silicene-based filtering device.

cond-mat.mes-hall↗