Journal of Physics. Condensed Matter : An Institute of Physics Journal

In the last decade, graphene has become an exciting platform for electron optical experiments, in some aspects superior to conventional two-dimensional electron gases (2DEGs). A major advantage, besides the ultra-large mobilities, is the fine control over the electrostatics,
which gives the possibility of realising gap-less and compact p-n interfaces with high precision. The latter host non-trivial states, \eg, snake states in moderate magnetic fields, and serve as building blocks of complex electron interferometers...

In this paper，a water-like pentamode metamaterial (PM) with a single metallic material is designed and the topological edge-state transmission properties of elastic waves in the PM are thoroughly investigated. Numerical results indicate that by introducing structural perturbation into PM, the Dirac point degeneracy at K-point can be opened and topological band inversion can be generated. Topological edge states are also obtained by organizing PM structural units, which are robust to defects such as bending and cavities...

Hole-doped cuprates exhibit partially coexisting pseudogap, charge ordering and superconductivity; we show that there exists a class of systems in which they have a single nature as it has recently been supposed. Since the charge-ordered phase exhibits large frozen deformation of the lattice, we develop a method for calculating the phase diagram of a system with strong long-range (Frӧhlich) electron-phonon interaction. Using a variational approach, we calculate the free energy of a two-liquid system of carriers with cuprate-like dispersion comprising a liquid of autolocalized carriers (large polarons and bipolarons) and Fermi liquid of delocalized carriers...

We investigate phonon thermal transport of fullerene-based single-molecule junctions by employing classical molecular dynamics simulations. 
The thermal conductances of fullerene monomers, dimers, and trimers are computed through three distinct molecular dynamics methods, by following the equilibration dynamics in one method, and using two other nonequilibrium simulation methods. We discuss technical aspects of the simulation techniques, and show that their predictions for the thermal conductance agree...

The thermal transport properties of mantle minerals are of paramount importance to understand the thermal evolution processes of the Earth. Here, we perform extensively structural searches of two-dimensional (2D) MgSiO3 monolayer by CALYPSO method and first-principles calculations. A stable MgSiO3 monolayer with Pmm 2 symmetry is uncovered, which possesses a wide indirect band gap of 4.39 eV. The calculations indicate the lattice thermal conductivities of MgSiO3 monolayer are 49.86 W/mK and 9.09 W/mK in x and y directions at room temperature...

Janus two dimensional (2D) materials are new and novel materials. As they break out-of-plane symmetry, they possess several fascinating properties which can be applied in catalytic reactions and opto-electronics. Recent synthesis of MoSH and the prediction of phonon-mediated superconductivity have opened a new way to investigate the properties of hydrogenated Janus materials [1-3]. In this work, we performed the density functional theory (DFT) calculations to demonstrate that titanium sulfur hydride (TiSH) is dynamically stable and becomes phonon-mediated superconductor with the superconducting critical temperature, Tc = 9...

The computation of thermal conductivity for finite nanoparticulate systems, particularly those of irregular shapes, poses significant challenges. Much of the previous work on the thermal conductivity of nanoparticles has been carried out by applying traditional nonequilibrium molecular dynamics (NEMD) methods. One of our recent works [Physical Review B 103, 035417 (2021)] proposed that equilibrium molecular dynamics (EMD) methods can be used for the simulation of thermal conductivity of finite-scale systems and demonstrated their equivalence to NEMD methods...

CoNb2 O6 is a model system for a spin-1/2 one-dimensional (1D) transverse-field Ising magnet (TFIM) with a rather low 3D Neel ordering temperature at T N = 2.95 K. We studied CoNb2 O6 using ultrasound measurements down to 0.3 K in transverse magnetic fields applied along the b direction. Upon entering the 3D ordered state, we observe pronounced anomalies in the transverse acoustic mode c 66 . In particular, from 1.3 to 1.5 K and around 4.7 T, this mode reveals an almost diverging softening, which is considerably reduced at lower and higher magnetic fields...

Phonon modes and their association with the electronic states have been
investigated for the metallic EuCu2 As2 system. In this work, we present the Raman
spectra of this pnictide system which clearly shows the presence of seven well defined
peaks above 100 cm-1 
that is consistent with the locally non-centrosymmetric P4/nmm
crystal structure, contrary to that what is expected from the accepted symmorphic
I4/mmm structure. Lattice dynamics calculations using the P4/nmm symmetry attest
that there is a commendable agreement between the calculated phonon spectra at
the Γ point and the observed Raman mode frequencies, with the most intense peak
at ∼ 232 cm-1 being ascribed to the A1g mode...

Alternating or sequence defined polymers attract the attention of an increasing number of researchers recently. Due to their different blocks, they are very customizable and material properties can be tuned. In this publication, we present dynamical studies with focus on polymer dynamics, investigated by rheology and fast field cycling NMR. The molecular weight dependencies of the relaxation time and zero-shear viscosity could hint to entanglement effects; however, the spectral shape of the viscoelastic data resembles the polymer dynamics of unentangled melts...

Recent studies have reported that lead-halide perovskites are the most efficient energy-harvesting materials. Regardless of their high-output energy and structural stability, lead-based products have risk factors due to their toxicity. Therefore, lead-free perovskites that offer green energy are the expected alternatives. We have taken CsGeX3 (X= Cl, Br, and I) as lead-free halide perovskites
despite knowing the low power conversion rate. Herein, we have tried to study the mechanisms of enhancement of energy-harvesting capabilities involving an interplay between structure and electronic properties...

Monomer, dimer and trimer semiconductor superlattices are an alternative for bandgap engineering due to the possibility of duplicate, triplicate and in general multiply the number of minibands and minigaps in a specific energy region. Here, we show that monomer, dimer and trimer magnetic silicene superlattices (MSSLs) can be the basis for tunable magnetoresistive devices due to the multiplication of the peaks of the tunneling magnetoresistance (TMR). In addition, these structures can serve as spin-valleytronic devices due to the formation of two well-defined spin-valley polarization states by adjusting appropriately the superlattice structural parameters...

Density functional simulations have been performed for Ptn Ni55-n clusters (n = 0,12,20,28,42,55) to investigate their catalytic properties for the hydrogen evolution reaction (HER). Starting from the icosahedral Pt12 Ni43 , hydrogen adsorption energetics and electronic d-band descriptors indicate HER activity comparable to that of pure Pt55 (distorted reduced core structure). The PtNi clusters accommodate a large number of adsorbed hydrogen before reaching a saturated coverage, corresponding to 3-4 H atoms per icosahedron facet (in total ∼70-80)...

This study performs extended X-ray absorption fine structure (EXAFS) measurements for the S-K edge in the temperature range of 10 and 300 K in the transmission mode using a photodiode to detect the transmitted X-rays. It provides the first report of temperature variations in the structural parameters of α-S. As the temperature increases from 10 to 300 K in the Fourier transform of kχ(k), the first peak corresponding to the covalent bond of the eight-membered ring becomes slightly low anomalously despite thermal disturbances...

Topological phases in kagome systems have garnered considerable interest since the introduction of the colloidal kagome lattice. Our study employs first-principle calculations and symmetry analysis to predict the existence of ideal type-I, III nodal rings, type-I, III quadratic nodal points, and Dirac valley phonons in a collection of two-dimensional kagome lattices M2C3 (M = As, Bi, Cd, Hg, P, Sb, Zn). Specifically, the Dirac valley points can be observed at two inequivalent valleys with Berry phases of +π and -π, connected by edge arcs along the zigzag and armchair directions...

We investigate the effect of a magnetic field on the band structure of bilayer graphene with a magic twist angle of 1.08°. The coupling of a tight-binding model and the Peierls phase allows the calculation of the energy bands of periodic two-dimensional systems. For an orthogonal magnetic field, the Landau levels are dispersive, particularly for magnetic lengths comparable to or larger than the twisted bilayer cell size. A high in-plane magnetic field modifies the low-energy bands and gap, which we demonstrate to be a direct consequence of the minimal coupling...

We investigated the band renormalization caused by the compressive-strain-induced lattice mismatch in parallel AA stacked bilayer graphene using two complementary methods: the tight-binding approach and the low-energy continuum theory. While a large mismatch does not alter the low-energy bands, a small one reduces the bandwidth of the low-energy bands along with a decrease in the Fermi velocity. In the tiny-mismatch regime, the low-energy continuum theory reveals that the long-period moir'e pattern extensively renormalizes the low-energy bands, resulting in a significant reduction of bandwidth...

Topological insulator (TI) surface states exert strong spin-orbit torques. When the magnetization is in the plane its interaction with the TI conduction electrons is non-trivial, and is influenced by extrinsic spin-orbit scattering. This is expected to be strong in TIs but is difficult to calculate and to measure unambiguously. Here we show that extrinsic spin-orbit scattering sizably renormalizes the surface state spin-orbit torque resulting in a strong density dependence. The magnitude of the renormalization of the spin torque and the effect of spin-orbit scattering on the relative sizes of the in-plane and out-of-plane field-like torques have strong implications for experiment: We propose two separate experimental signatures for the measurement of its presence...

The effect of negative chemical pressure with the substitution of transition metal V in an itinerant helimagnetically ordered MnSi, Mn1- x V x Si with x = 0-0.1, is explored using dc and ac-susceptibilities. With increasing x , the manifestations are unaffected crystal structure with increasing unit cell volume, suppression of long-range magnetic order, weakening of itinerant character and reduced spin-cooperative phenomenon. The emergence of spin-glass behaviour for x ≥ 0.1 intervenes in the occurrence of quantum phase transition...

A comprehensive study of structural and magnetotransport properties of pristine Bi2-xSbxTe3-ySey (BSTS) single crystals and doped with Zn (BSTS:Zn) and Ga (BSTS:Ga) are presented here. Magnetic field dependent Hall resistivities of the single crystals indicate that the holes are the majority carriers. The field dependent resistivity curves at different temperatures of the crystals display cusp-like characteristics at low magnetic fields, attributed to two-dimensional (2D) weak antilocalization (WAL) effect...