Abstract
The non-ambiguous experimental identification of topological states of matter is one of the main interesting problems regarding this new quantum state of matter. In particular, the half-Heusler family RMT (R = rare-earth, T = Pd, Pt or Au and T = Bi, Sb, Pb or Sn) could be a useful platform to explore these states due to their cubic symmetry and the topological properties tunable via their unit cell volume and/or the nuclear charges of the M and T atoms. In this work, we report electron spin resonance (ESR) and complementary macroscopic measurements in the Nd3 + -doped putative topologically trivial semimetal YPdBi. Following the Nd3 + ESR lineshape as a function of microwave power, size of the particle and temperature, we have been able to observe an evolution from a Dysonian lineshape to a diffusive-like lineshape. Furthermore, the Nd3 + ESR intensity saturation is concentration dependent, which could be due to a phonon-bottleneck process. Comparing these results with the Nd3 + -doped YPtBi, we discuss a possible scenario in which the Nd3 + ions could locally tune the topological properties of the system.
Highlights
A new quantum state of matter,[1] the three dimensional topological insulators (3D TIs) has become a hot topic intensively explored by the community in order to understand their properties and the application of the topology in condensed matter physics.[2,3] The nontrivial insulators with gapless surface states, protected from backscattering and with highly spin polarized channels, have been the trigger to study a new field of topological systems
The Nd3 + g-value observed for those electron spin resonance (ESR) were g = 2.641(1), which is consistent with a Γ6 cubic crystalline electrical field (CEF) ground state.[17]
In order to look for diffusive effects, we have focused in the Nd3 + ESR in single crystals, which is shown in Fig. 3 for a) x = 0.01, b) x = 0.03 and c) x = 0.1
Summary
A new quantum state of matter,[1] the three dimensional topological insulators (3D TIs) has become a hot topic intensively explored by the community in order to understand their properties and the application of the topology in condensed matter physics.[2,3] The nontrivial insulators with gapless surface states, protected from backscattering and with highly spin polarized channels, have been the trigger to study a new field of topological systems. In Dyson model, the LMESR is described in the diffusion-less regime, in other words, the diffusive time across the skin depth of the local moment TD is negligible compared with the spin-spin transverse relaxation time T 2 In this limit, the lineshape is asymmetric with a ratio A/B 2.6 (defined in Fig. 2 a)) and is called Dysonian. In order to verify this hypothesis in a counterpart compound in the same family, we report a systematic ESR study in Y1 xNdxPdBi. The YPdBi is on the frontier of topological triviality and non-triviality[12,13,14] and could be a useful platform to contrast with the previous results reported for YPtBi. Recent crystalline electrical field (CEF) studies[19,20] show a systematic change in the sign of the crystal field parameters (CFP) comparing the YPdBi and the YPtBi compounds. Due to the fact that the YPdBi is on the frontier of trivial and nontrivial materials, those effects should be more pronounced in the YPdBi case, making a compelling case to be compared with YPtBi
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