Subscribe to the gold package and get unlimited access to Shamra Academy
Register a new userNon-saturating magnetoresistance of inhomogeneous conductors: comparison of experiment and simulation
123
0
0.0
(
0
)
Ask ChatGPT about the research
No Arabic abstract
The silver chalcogenides provide a striking example of the benefits of imperfection. Nanothreads of excess silver cause distortions in the current flow that yield a linear and non-saturating transverse magnetoresistance (MR). Associated with the large and positive MR is a negative longitudinal MR. The longitudinal MR only occurs in the three-dimensional limit and thereby permits the determination of a characteristic length scale set by the spatial inhomogeneity. We find that this fundamental inhomogeneity length can be as large as ten microns. Systematic measurements of the diagonal and off-diagonal components of the resistivity tensor in various sample geometries show clear evidence of the distorted current paths posited in theoretical simulations. We use a random resistor network model to fit the linear MR, and expand it from two to three dimensions to depict current distortions in the third (thickness) dimension. When compared directly to experiments on Ag$_{2pmdelta}$Se and Ag$_{2pmdelta}$Te, in magnetic fields up to 55 T, the model identifies conductivity fluctuations due to macroscopic inhomogeneities as the underlying physical mechanism. It also accounts reasonably quantitatively for the various components of the resistivity tensor observed in the experiments.
rate research
Read More
The observation of non-saturating classical linear magnetoresistivity has been an enigmatic phenomenon in solid state physics. We present a study of a two-dimensional ohmic conductor, including local Hall effect and a self-consistent consideration of the environment. An equivalent-circuit scheme delivers a simple and convincing argument why the magnetoresistivity is linear in strong magnetic field, provided that current and biasing electric field are misaligned by a nonlocal mechanism. A finite-element model of a two-dimensional conductor is suited to display the situations that create such deviating currents. Besides edge effects next to electrodes, charge carrier density fluctuations are efficiently generating this effect. However, mobility fluctuations that have frequently been related to linear magnetoresistivity are barely relevant. Despite its rare observation, linear magnetoresitivity is rather the rule than the exception in a regime of low charge carrier densities, misaligned current pathways and strong magnetic field.
We present a detailed study of magnetoresistance r{ho}xx(H), Hall effect r{ho}xy(H), and electrolyte gating effect in thin (<100 nm) exfoliated crystals of WTe2. We observe quantum oscillations in H of both r{ho}xx(H) and r{ho}xy(H), and identify four oscillation frequencies consistent with previous reports in thick crystals. r{ho}xy(H) is linear in H at low H consistent with near-perfect electron-hole compensation, however becomes nonlinear and changes sign with increasing H, implying a breakdown of compensation. A field-dependent ratio of carrier concentrations p/n can consistently explain r{ho}xx(H) and r{ho}xy(H) within a two-fluid model. We also employ an electrolytic gate to highly electron-dope WTe2 with Li. The non-saturating r{ho}xx(H) persists to H = 14 T with magnetoresistance ratio exceeding 2 x 104 %, even with significant deviation from perfect electron-hole compensation (p/n = 0.84), where the two-fluid model predicts a saturating r{ho}xx(H). Our results suggest electron-hole compensation is not the mechanism for extremely large magnetoresistance in WTe2, other alternative explanations need to be considered.
The dielectric response in a magnetic field is routinely used to probe the existence of coupled magnetic and elastic order in the multiferroics. However, here we demonstrate that magnetism is not necessary to produce a magnetocapacitance when the material is inhomogeneous. By considering a two-dimensional, two-component composite medium, we find a characteristic dielectric resonance that depends on magnetic field. We propose this as a possible signature of inhomogeneities and we argue that this behavior has already been observed in nanoporous silicon and some manganites.
We report the detailed electronic structure of WTe$_2$ by high resolution angle-resolved photoemission spectroscopy. Unlike the simple one electron plus one hole pocket type of Fermi surface topology reported before, we resolved a rather complicated Fermi surface of WTe$_2$. Specifically, there are totally nine Fermi pockets, including one hole pocket at the Brillouin zone center $Gamma$, and two hole pockets and two electron pockets on each side of $Gamma$ along the $Gamma$-$X$ direction. Remarkably, we have observed circular dichroism in our photoemission spectra, which suggests that the orbital angular momentum exhibits a rich texture at various sections of the Fermi surface. As reported previously for topological insulators and Rashiba systems, such a circular dichroism is a signature for spin-orbital coupling (SOC). This is further confirmed by our density functional theory calculations, where the spin texture is qualitatively reproduced as the conjugate consequence of SOC. Since the backscattering processes are directly involved with the resistivity, our data suggest that the SOC and the related spin and orbital angular momentum textures may be considered in the understanding of the anomalous magnetoresistance of WTe$_2$.
We report experimental observations of a novel magnetoresistance (MR) behavior of two-dimensional electron systems in perpendicular magnetic field in the ballistic regime, for k_BTtau/hbar>1. The MR grows with field and exhibits a maximum at fields B>1/mu, where mu is the electron mobility. As temperature increases the magnitude of the maximum grows and its position moves to higher fields. This effect is universal: it is observed in various Si- and GaAs- based two-dimensional electron systems. We compared our data with recent theory based on the Kohn anomaly modification in magnetic field, and found qualitative similarities and discrepancies.
Log in to be able to interact and post comments
comments
Fetching comments
Sign in to be able to follow your search criteria
