Lesson 3: Topological Spin Transport & Entanglement in Quantum Materials

Courses

Speaker
Stephan Roche
Institut Català de Nanociència i Nanotecnologia (ICN2), Barcelona, Spain
When
2024/07/16
11:30
Place
DIPC seminar room
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Lesson 3: Topological Spin Transport & Entanglement in Quantum Materials

I will present theoretical spin transport features in MoTe2 and WTe2-based materials which are particularly interesting Quantum Materials. By focusing on the monolayer limit, using DFT-derived tight-binding models, and using both efficient bulk and multi-terminal formalisms and techniques [1-4], I will show the emergence of new forms of intrinsic spin Hall effect (SHE) that produce large and robust in-plane spin polarizations. Quantum transport calculations on realistic device geometries with disorder demonstrate large charge-to-spin interconversion efficiency with gate tunable spin Hall angle as large as θxy≈80%, and SHE figure of merit λs.θxy∼8-10 nm, largely superior to any known SHE material [1]. I will also show our theoretical prediction of an unconventional canted quantum spin Hall phase in the monolayer Td-WTe2, which exhibits hitherto unknown features in other topological materials [2]. The low symmetry of the structure induces a canted spin texture in the yz plane, dictating the spin polarization of topologically protected boundary states. Additionally, the spin Hall conductivity gets quantized (2e2/h) with a spin quantization axis parallel to the canting direction. We have predicted the control of the canted QSHE by electric field [3]. I will also present some recent results on very large spin-orbit torque phenomena in Janus transition metal dichalcogenide materials and other topological features [4].

I will finally discuss the role of entanglement between intraparticle degrees of freedom in spin transport and dynamical patterns of entanglement, as enabling novel platform for generating and manipulating quantum entanglement between internal and interparticle degrees of freedom [5].

 References

  1. Vila, C.H. Hsu, J.H. Garcia, L.A. Benítez, X. Waintal, S. Valenzuela, V. Pereira, S. Roche, “Charge-to-Spin Interconversion in Low-Symmetry Topological Materials”, Physical Review Research 3, 043230 (2021)
  2. H. Garcia, M. Vila, C.H. Hsu, X. Waintal, V.M. Pereira, S. Roche, “Canted Persistent Spin Texture and Quantum Spin Hall Effect in WTe2, Physical Review Letters 125 (25), 256603 (2020)
  3. JH Garcia, J You, et al. S. Roche, “ Electrical control of spin-polarized topological currents in monolayer Physical Review B 106 (16), L161410 (2022)
  4. Vojacek et al. submitted to Physical Review Letters; J. Medina Dueñas et al, unpublished.
  5. BG de Moraes, AW Cummings, S Roche, “Emergence of intraparticle entanglement and time-varying violation of Bell's inequality in Dirac matter”, Physical Review B 102 (4), 041403 (2020); J. Martinez, A.W. Cummings and S. Roche arXiv preprint arXiv:2310.17950