TY  - JOUR
A1  - Gottscholl, Andreas
A1  - Diez, Matthias
A1  - Soltamov, Victor
A1  - Kasper, Christian
A1  - Krauße, Dominik
A1  - Sperlich, Andreas
A1  - Kianinia, Mehran
A1  - Bradac, Carlo
A1  - Aharonovich, Igor
A1  - Dyakonov, Vladimir
T1  - Spin defects in hBN as promising temperature, pressure and magnetic field quantum sensors
JF  - Nature Communications
N2  - Spin defects in solid-state materials are strong candidate systems for quantum information technology and sensing applications. Here we explore in details the recently discovered negatively charged boron vacancies (V\(_B\)\(^−\)) in hexagonal boron nitride (hBN) and demonstrate their use as atomic scale sensors for temperature, magnetic fields and externally applied pressure. These applications are possible due to the high-spin triplet ground state and bright spin-dependent photoluminescence of the V\(_B\)\(^−\). Specifically, we find that the frequency shift in optically detected magnetic resonance measurements is not only sensitive to static magnetic fields, but also to temperature and pressure changes which we relate to crystal lattice parameters. We show that spin-rich hBN films are potentially applicable as intrinsic sensors in heterostructures made of functionalized 2D materials.
KW  - electronic properties and materials
KW  - qubits
Y1  - 2021
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-261581
VL  - 12
IS  - 1
ER  - 
TY  - JOUR
A1  - Ünzelmann, M.
A1  - Bentmann, H.
A1  - Figgemeier, T.
A1  - Eck, P.
A1  - Neu, J. N.
A1  - Geldiyev, B.
A1  - Diekmann, F.
A1  - Rohlf, S.
A1  - Buck, J.
A1  - Hoesch, M.
A1  - Kalläne, M.
A1  - Rossnagel, K.
A1  - Thomale, R.
A1  - Siegrist, T.
A1  - Sangiovanni, G.
A1  - Di Sante, D.
A1  - Reinert, F.
T1  - Momentum-space signatures of Berry flux monopoles in the Weyl semimetal TaAs
JF  - Nature Communications
N2  - Since the early days of Dirac flux quantization, magnetic monopoles have been sought after as a potential corollary of quantized electric charge. As opposed to magnetic monopoles embedded into the theory of electromagnetism, Weyl semimetals (WSM) exhibit Berry flux monopoles in reciprocal parameter space. As a function of crystal momentum, such monopoles locate at the crossing point of spin-polarized bands forming the Weyl cone. Here, we report momentum-resolved spectroscopic signatures of Berry flux monopoles in TaAs as a paradigmatic WSM. We carried out angle-resolved photoelectron spectroscopy at bulk-sensitive soft X-ray energies (SX-ARPES) combined with photoelectron spin detection and circular dichroism. The experiments reveal large spin- and orbital-angular-momentum (SAM and OAM) polarizations of the Weyl-fermion states, resulting from the broken crystalline inversion symmetry in TaAs. Supported by first-principles calculations, our measurements image signatures of a topologically non-trivial winding of the OAM at the Weyl nodes and unveil a chirality-dependent SAM of the Weyl bands. Our results provide directly bulk-sensitive spectroscopic support for the non-trivial band topology in the WSM TaAs, promising to have profound implications for the study of quantum-geometric effects in solids. Weyl semimetals exhibit Berry flux monopoles in momentum-space, but direct experimental evidence has remained elusive. Here, the authors reveal topologically non-trivial winding of the orbital-angular-momentum at the Weyl nodes and a chirality-dependent spin-angular-momentum of the Weyl bands, as a direct signature of the Berry flux monopoles in TaAs.
KW  - electronic properties and materials
KW  - topological insulators
Y1  - 2021
U6  - http://nbn-resolving.de/urn/resolver.pl?urn:nbn:de:bvb:20-opus-260719
VL  - 12
IS  - 1
ER  -