CdAs is a Dirac semimetal that is a 3D analog of graphene. We investigated the local structure and nuclear-spin dynamics in CdAs via Cd NMR. The wideline spectrum of the static sample at 295 K is asymmetric and its features are well described by a two-site model with the shielding parameters extracted via Herzfeld-Berger analysis of the magic-angle spinning spectrum. Surprisingly, the Cd spin-lattice relaxation time (T) is extremely long (T = 95 s at 295 K), in stark contrast to conductors and the effects of native defects upon semiconductors; but it is similar to that of C in graphene (T = 110 s). The temperature dependence of 1/T revealed a complex bipartite mechanism that included a T power-law behavior below 330 K and a thermally activated process above 330 K. In the high-temperature regime, the Arrhenius behavior is consistent with a field-dependent Cd atomic hopping relaxation process. At low temperatures, a T behavior consistent with a spin-1/2 Raman-like process provides evidence of a time-dependent spin-rotation magnetic field caused by angular oscillations of internuclear vectors due to lattice vibrations. The observed mechanism does not conform to the conventional two-band model of semimetals, but is instead closer to a mechanism observed in high-Z element ionic solids with large magnetorotation constant [A. J. Vega et al., Phys. Rev. B 74, 214420 (2006)].
Download full-text PDF |
Source |
|---|---|
| http://dx.doi.org/10.1063/1.4999467 | DOI Listing |
Publication Analysis
Top Keywords
Similar Publications
Phase transitions, Dirac and Weyl semimetal states in MnGeBiTe.
Sci Rep
January 2025
Saint Petersburg State University, St. Petersburg, 198504, Russia.
Using angle-resolved photoemission spectroscopy (ARPES) and density functional theory (DFT), an experimental and theoretical study of changes in the electronic structure (dispersion dependencies) and corresponding modification of the energy band gap at the Dirac point (DP) for topological insulator (TI) [Formula: see text] have been carried out with gradual replacement of magnetic Mn atoms by non-magnetic Ge atoms when concentration of the latter was varied from 10% to 75%. It was shown that when Ge concentration increases, the bulk band gap decreases and reaches zero plateau in the concentration range of 45-60% while trivial surface states (TrSS) are present and exhibit an energy splitting of 100 and 70 meV in different types of measurements. It was also shown that TSS disappear from the measured band dispersions at a Ge concentration of about 40%.
View Article and Find Full Text PDFDirect Observation of Anisotropic Coulomb Interaction in a Topological Nodal Line Semimetal.
Adv Sci (Weinh)
January 2025
Department of Physics, Chung-Ang University, Seoul, 06974, Republic of Korea.
The fundamental characteristics of collective interactions in topological band structures can be revealed by the exploration of charge screening in topological materials. In particular, distinct anisotropic screening behaviors are predicted to occur in Dirac nodal line semimetals (DNLSMs) due to their peculiar anisotropic low-energy dispersion. Despite the recent extensive theoretical research, experimental observations of exotic charge screening in DNLSMs remain elusive, which is partly attributed to the coexisting trivial bands near the Fermi energy.
View Article and Find Full Text PDFCorrelated Dirac Fermions in Twisted Bilayers of MoS.
Nano Lett
January 2025
Beijing Computational Science Research Center, Beijing 100193, China.
Artificial honeycomb lattices are essential for understanding exotic quantum phenomena arising from the interplay between Dirac physics and electron correlation. This work shows that the top two moiré valence bands in rhombohedral-stacked twisted MoS bilayers (tb-MoS) form a honeycomb lattice with massless Dirac fermions. The hopping and Coulomb interaction parameters are explicitly determined based on large-scale ab initio calculations.
View Article and Find Full Text PDFAtomic Manipulation on 2D Sumanene for Precise Fermi Level Positioning in Ultrafast High-Capacity Alkali Metal Batteries.
Nano Lett
January 2025
State Key Laboratory of Structural Analysis for Industrial Equipment & School of Physics, Dalian University of Technology, Dalian 116024 People's Republic of China.
Article Synopsis
- A sumanene monolayer with a unique Kagome-like lattice features two flat bands and two Dirac cones, which can be designed using carbon clusters.
- First-principles simulations show that surface charge doping can effectively adjust the Fermi level between these bands, allowing for the transformation of the semiconducting monolayer into a semimetal using Li/Na/K atoms.
- This doped sumanene exhibits high theoretical storage capacity, rapid charge capability, and exceptional structural stability, making it an attractive anode material for alkali-metal batteries.
Multipocket synergy towards high thermoelectric performance in topological semimetal TaAs.
Nat Commun
January 2025
Max Planck Institute for Chemical Physics of Solids, Nöthnitzer Str. 40, Dresden, Germany.
Charge-carrier compensation in topological semimetals amplifies the Nernst signal and simultaneously degrades the Seebeck coefficient. In this study, we report the simultaneous achievement of both a large Nernst signal and an unsaturating magneto-Seebeck coefficient in a topological nodal-line semimetal TaAs single crystal. The unique dual-high transverse and longitudinal thermopowers are attributed to multipocket synergy effects: the combination of a strong phonon-drag effect and the two overlapping highly dispersive conduction and valence bands with electron-hole compensation and high mobility, promising a large Nernst effect; the third Dirac band causes a large magneto-Seebeck effect.
View Article and Find Full Text PDFWant AI Summaries of new PubMed Abstracts delivered to your In-box?
Enter search terms and have AI summaries delivered each week - change queries or unsubscribe any time!