Advances in scaling down heterostructures and having an improved interface quality together with atomically thin two-dimensional materials suggest a novel approach to systematically design materials. A given material can be transformed through proximity effects whereby it acquires properties of its neighbors, for example, becoming superconducting, magnetic, topologically nontrivial, or enhanced spin–orbit coupling. Such not only complement the conventional methods designing by doping...

The two-dimensional character and reduced screening in monolayer transition-metal dichalcogenides (TMDs) lead to the ubiquitous formation of robust excitons with binding energies orders magnitude larger than bulk semiconductors. Focusing on neutral excitons, bound electron-hole pairs that dominate optical response TMDs, it is shown they can provide fingerprints for magnetic proximity effects heterostructures. These cannot be described by widely used single-particle description but instead...

We propose a versatile platform to investigate the existence of Majorana bound states (MBSs) and their non-Abelian statistics through braiding. This implementation combines two-dimensional electron gas formed in semiconductor quantum well grown on surface an s-wave superconductor with nearby array magnetic tunnel junctions (MTJs). The underlying textures produced by MTJs provide highly controllable topological phase transitions confine transport MBSs two dimensions, overcoming requirement...

Many-body interactions in monolayer transition-metal dichalcogenides are strongly affected by their unique band structure. We study these measuring the energy shift of neutral excitons (bound electron-hole pairs) gated ${\mathrm{WSe}}_{2}$ and ${\mathrm{MoSe}}_{2}$. Surprisingly, while blueshift exciton ${X}^{0}$ electron-doped samples can be more than 10 meV, hole-doped is nearly absent. Taking into account dynamical screening local-field effects, we present a transparent analytical model...

Using analytical formulas as well a finite-difference scheme, we investigate the magnetic field dependence of energy spectra and edge states HgTe/CdTe-based quantum wells in presence perpendicular fields hard walls for band-structure parameters corresponding to normal inverted regimes. Whereas one can not find counterpropagating, spin-polarized regime, below crossover point between uppermost (electronlike) valence lowest (holelike) conduction Landau levels, still observe such at finite...

We theoretically investigate the frictional drag induced by Coulomb interaction between spa- tially separated massless and massive fermions at low temperatures. As a model system, we use double-layer structure composed of two-dimensional electron gas (2DEG) n-doped graphene layer. analyze this system numerically also present analytical formulae for re- sistivity in limit large small interlayer separation. Both, temperature density dependence are investigated compared to 2DEG-2DEG...

We theoretically investigate excitons in MoS$_2$ monolayers an applied in-plane electric field. Tight-binding and Bethe-Salpeter equation calculations predict a quadratic Stark shift, of the order few meV for fields 10 V/$\mu$m, linear absorption spectra. The spectral weight main exciton peaks decreases by percent with increasing field due to ionization into free carriers as reflected wave functions. Subpicosecond decay lifetimes at tens V/$\mu$m could be utilized solar energy harvesting...

Recently, topological superconductors based on Josephson junctions in two-dimensional electron gases with strong Rashba spin-orbit coupling have been proposed as attractive alternatives to wire-based setups. Here, we elucidate how phase-controlled quantum wells [001] growth direction and an arbitrary combination of Dresselhaus can also host Majorana bound states for a wide range parameters long the magnetic field is oriented appropriately. Hence, appear class gases. We study effect coupling,...

Using the Kubo linear response formalism, we study effects of intrinsic graphene optical and surface polar phonons (SPPs) on conductivity doped graphene. We find that inelastic electron-phonon scattering contributes significantly to phonon-assisted absorption in gap. At room temperature, this midgap can be as large 20-25% universal ac for substrates due strong electron-SPP coupling. The absorption, moreover, strongly depends doping levels used. With increasing increases, while Drude peak,...

We theoretically study the effect of polar substrates on magneto-optical conductivity doped monolayer graphene, where we particularly focus role played by surface phonons (SPPs). Our calculations suggest that polaronic shifts intra- and interband absorption peaks can be significantly larger for with strong electron-SPP coupling than those in graphene nonpolar substrates, only intrinsic optical much higher energies contribute. Electron-phonon scattering phonon-assisted transitions are,...

Just as photons are the quanta of light, plasmons orchestrated charge-density oscillations in conducting media. Plasmon phenomena normal metals, superconductors and doped semiconductors often driven by long-wavelength Coulomb interactions. However, crystals whose Fermi surface is comprised disconnected pockets Brillouin zone, collective electron excitations can also attain a shortwave component when electrons transition between these pockets. Here, we show that band structure monolayer...

We analyze the detailed structure of topological edge mode protection occuring in hexagonal quantum spin Hall (QSH) materials. focus on bismuthene, antimonene, and arsenene a SiC substrate, which, due to their large bulk gap, may offer new opportunities for room-temperature QSH applications. While time reversal symmetry is responsible principal protected character states, terminations yield further aspects crystal which affect protection. show that armchair states remain gapless under an...

We investigate tunneling across a single ferromagnetic barrier on the surface of three-dimensional topological insulator. In presence magnetization component along bias direction, planar Hall conductance (TPHC), transverse to applied bias, develops. Electrostatic control enables giant angle, with TPHC exceeding longitudinal conductance. By changing in-plane it is possible change sign both and differential without opening gap in state. The transport topological-insulator-ferromagnet junction...

Monolayer transition-metal dichalcogenides (ML-TMDs) offer exciting opportunities to test the manifestations of many-body interactions through changes in charge density. The two-dimensional character and reduced screening ML-TMDs lead formation neutral charged excitons with binding energies orders magnitude larger than those conventional bulk semiconductors. Tuning density by a gate voltage leads profound optical spectra ML-TMDs. On one hand, increased at large densities should result...

Optical properties in van der Waals heterostructures based on monolayer transition-metal dichalcogenides (TMDs) are often dominated by excitonic transitions. While intrinsic spin-orbit coupling (SOC) and an isotropic band structure typically studied TMDs, their Rashba SOC trigonal warping (TW), resulting bands with threefold anisotropy, also present. By considering a low-energy effective Hamiltonian Bethe-Salpeter equation, we study the effect of TW absorption spectra. is predicted to lead...

In many atomically thin materials their optical absorption is dominated by excitonic transitions. It was recently found that selection rules in these are influenced the band topology near valleys. We propose gate-controlled ordering a single atomic monolayer, through changes valley winding number and transitions, can be probed helicity-resolved photoluminescence. This predicted tunable confirmed combining an effective Hamiltonian Bethe-Salpeter equation for accurate description of excitons,...

Abstract The scientific interest in two-dimensional topological insulators (2D TIs) is currently shifting from a more fundamental perspective to the exploration and design of novel functionalities. Key concepts for use 2D TIs spintronics are based on protection spin-momentum locking their helical edge states. In this study we present experimental evidence that can be (partially) lifted by pairwise coupling TI edges close proximity. Using direct wave function mapping via scanning tunneling...

The superconducting diode effect (SDE) is a magnetoelectric phenomenon where an external magnetic field imparts nonzero center-of-mass momentum to Cooper pairs, either facilitating or hindering the flow of supercurrent depending on its direction. We propose that quantum spin Hall insulator (QSHI)-based Josephson junctions can serve as versatile platforms for nondissipative electronics exhibiting SDE when triggered by phase bias and out-of-plane field. By computing contributions from Andreev...

The interplay between spin transport and thermoelectricity offers several novel ways of generating, manipulating, detecting nonequilibrium in a wide range materials. Here we formulate phenomenological model the spirit standard electrical injection to describe electronic mechanism coupling charge, spin, heat employ analyze different geometries containing ferromagnetic (F) nonmagnetic (N) regions: F, F/N, F/N/F junctions which are subject thermal gradients. We present analytical formulas for...

In two-dimensional topological insulators, such as inverted HgTe/CdTe quantum wells, helical spin Hall (QSH) states persist even at finite magnetic fields below a critical field ${B}_{\mathrm{c}}$, above which only (QH) can be found. Using linear-response theory, we theoretically investigate the magneto-optical properties of both for infinite and finite-strip geometries possible signatures transition between QSH QH regimes. absorption spectrum, several peaks arise due to nonequidistant...

The promise of fault-tolerant quantum computing has made topological superconductors the focus intense research during past decade. In this context, Josephson junctions based on nanowires or insulators provide an alternative route for probing superconductivity. As a hallmark their nature, such exhibit ground-state fermion parity that is $4\pi$-periodic in superconducting phase difference $\phi$. Finding unambiguous experimental evidence $4\pi$-periodicity still proves difficult task,...

Layered materials enable the assembly of a new class heterostructures where lattice-matching is no longer requirement. Interfaces in these therefore become fertile ground for unexplored physics as dissimilar phenomena can be coupled via proximity effects. In this article, we identify an unexpected photoluminescence (PL) peak when MoSe2 interacts with TiSe2. A series temperature-dependent and spatially resolved PL measurements reveal that unique to TiSe2–MoSe2 interface, higher energy...

Engineering chiral $p$-wave superconductivity in semiconductor structures offers fascinating ways to obtain and study Majorana modes a condensed-matter context. Here, we theoretically investigate quantum dots rings. Using both analytical as well numerical methods, calculate the quasiparticle excitation spectra these corresponding amplitudes charge densities. In topological regime, can observe edge localized at boundaries possessing finite energy By applying magnetic field which is expelled...