Subscribe to the gold package and get unlimited access to Shamra Academy
Register a new userMetal-insulator transition in quasi-one-dimensional HfTe3 in the few-chain limit
265
0
0.0
(
0
)
Ask ChatGPT about the research
No Arabic abstract
The quasi-one-dimensional linear chain compound HfTe3 is experimentally and theoretically explored in the few- to single-chain limit. Confining the material within the hollow core of carbon nanotubes allows isolation of the chains and prevents the rapid oxidation which plagues even bulk HfTe3. High-resolution transmission electron microscopy combined with density functional theory calculations reveals that, once the triple-chain limit is reached, the normally parallel chains spiral about each other, and simultaneously a short-wavelength trigonal anti-prismatic rocking distortion occurs that opens a significant energy gap. This results in a size-driven metal-insulator transition.
rate research
Read More
The nature of the metal insulator transition in thin films and superlattices of LaNiO3 with only few unit cells in thickness remains elusive despite tremendous effort. Quantum confinement and epitaxial strain have been evoked as the mechanisms, although other factors such as growth-induced disorder, cation non-stoichiometry, oxygen vacancies, and substrate-film interface quality may also affect the observable properties in the ultrathin films. Here we report results obtained for near-ideal LaNiO3 films with different thicknesses and terminations grown by atomic layer-by-layer laser molecular beam epitaxy on LaAlO3 substrates. We find that the room-temperature metallic behavior persists until the film thickness is reduced to an unprecedentedly small 1.5 unit cells (NiO2 termination). Electronic structure measurements using x-ray absorption spectroscopy and first-principles calculation suggest that oxygen vacancies existing in the films also contribute to the metal insulator transition.
The formation of interfacial moire patterns from angular and/or lattice mismatch has become a powerful approach to engineer a range of quantum phenomena in van der Waals heterostructures. For long-lived and valley-polarized interlayer excitons in transition-metal dichalcogenide (TMDC) heterobilayers, signatures of quantum confinement by the moire landscape have been reported in recent experimental studies. Such moire confinement has offered the exciting possibility to tailor new excitonic systems, such as ordered arrays of zero-dimensional (0D) quantum emitters and their coupling into topological superlattices. A remarkable nature of the moire potential is its dramatic response to strain, where a small uniaxial strain can tune the array of quantum-dot-like 0D traps into parallel stripes of one-dimensional (1D) quantum wires. Here, we present direct evidence for the 1D moire potentials from real space imaging and the corresponding 1D moire excitons from photoluminescence (PL) emission in MoSe2/WSe2 heterobilayers. Whereas the 0D moire excitons display quantum emitter-like sharp PL peaks with circular polarization, the PL emission from 1D moire excitons has linear polarization and two orders of magnitude higher intensity. The results presented here establish strain engineering as a powerful new method to tailor moire potentials as well as their optical and electronic responses on demand.
Symmetry, dimensionality, and interaction are crucial ingredients for phase transitions and quantum states of matter. As a prominent example, the integer quantum Hall effect (QHE) represents a topological phase generally regarded as characteristic for two-dimensional (2D) electronic systems, and its many aspects can be understood without invoking electron-electron interaction. The intriguing possibility of generalizing QHE to three-dimensional (3D) systems was proposed decades ago, yet it remains elusive experimentally. Here, we report clear experimental evidence for the 3D QHE observed in bulk ZrTe5 crystals. Owing to the extremely high sample quality, the extreme quantum limit with only the lowest Landau level occupied can be achieved by an applied magnetic field as low as 1.5 T. Remarkably, in this regime, we observe a dissipationless longitudinal resistivity rho_xx=0 accompanied with a well-developed Hall resistivity plateau rho_xy=(1pm0.1) h/e^2 (lambda_(F,z)/2), where lambda_(F,z) is the Fermi wavelength along the field direction (z axis). This striking result strongly suggests a Fermi surface instability driven by the enhanced interaction effects in the extreme quantum limit. In addition, with further increasing magnetic field, both rho_xx and rho_xy increase dramatically and display an interesting metal-insulator transition, representing another magnetic field driven quantum phase transition. Our findings not only unambiguously reveal a novel quantum state of matter resulting from an intricate interplay among dimensionality, interaction, and symmetry breaking, but also provide a promising platform for further exploration of more exotic quantum phases and transitions in 3D systems.
Assembling transition metal dichalcogenides (TMDCs) at the two-dimensional (2D) limit is a promising approach for tailoring emerging states of matter such as superconductivity or charge density waves (CDWs). Single-layer (SL) VSe$_2$ stands out in this regard because it exhibits a strongly enhanced CDW transition with a higher transition temperature compared to the bulk in addition to an insulating phase with an anisotropic gap at the Fermi level, causing a suppression of anticipated 2D ferromagnetism in the material. Here, we investigate the interplay of electronic and lattice degrees of freedom that underpin these electronic phases in SL VSe$_2$ using ultrafast pump-probe photoemission spectroscopy. In the insulating state, we observe a light-induced closure of the energy gap on a timescale of 480 fs, which we disentangle from the ensuing hot carrier dynamics. Our work thereby reveals that the phase transition in SL VSe$_2$ is driven by electron-lattice coupling and demonstrates the potential for controlling electronic phases in 2D materials with light.
We study spectral statistics of one-dimensional quasi-periodic systems at the metal-insulator transition. Several types of spectral statistics are observed at the critical points, lines, and region. On the critical lines, we find the bandwidth distribution $P_B(w)$ around the origin (in the tail) to have the form of $P_B(w) sim w^{alpha}$ ($P_B(w) sim e^{-beta w^{gamma}}$) ($alpha, beta, gamma > 0 $), while in the critical region $P_B(w) sim w^{-alpha}$ ($alpha > 0$). We also find the level spacing distribution to follow an inverse power law $P_G(s) sim s^{- delta}$ ($delta > 0$)
Log in to be able to interact and post comments
comments
Fetching comments
Sign in to be able to follow your search criteria
