2018/06/29 by Su‐Yang Xu, Su-Yang Xu, Qiong Ma +22
Chemistry · Materials Science · Mathematics · Physics and Astronomy · #Berry connection and curvature #Combinatorics #Condensed matter physics #Curvature #Dipole #Fullerene Chemistry and Applications #Geometric phase #Geometry #Graphene research and applications #Insulator (electricity) #Materials science #Mathematics #Monolayer #Nanotechnology #Optoelectronics #Physics #Quantum mechanics #Topological Materials and Phenomena #Topological insulator #Topology (electrical circuits) #cond-mat.mes-hall
paper · pdf · doi:10.1038/s41567-018-0189-6
published as Nature Physics (2018), Advance Online · Originally submitted version, main text combined with part of the SI
openalex publication_date 2018/06/29 · arxiv created 2018/07/03 · arxiv updated 2018/07/04 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/06
Recent experimental evidence for the quantum spin Hall (QSH) state in monolayer WTe2 has bridged two of the most active fields of condensed matter physics, 2D materials and topological physics. This 2D topological crystal also displays unconventional spin-torque and gate-tunable superconductivity. While the realization of QSH has demonstrated the nontrivial topology of the electron wavefunctions of monolayer WTe2, the geometrical properties of the wavefunction, such as the Berry curvature, remain unstudied. On the other hand, it has been increasingly recognized that the Berry curvature plays an important role in multiple areas of condensed matter physics including nonreciprocal electron transport, enantioselective optical responses, chiral polaritons and even unconventional superconductivity. Here we utilize mid-infrared optoelectronic microscopy to investigate the Berry curvature in monolayer WTe2. By optically exciting electrons across the inverted QSH gap, we observe an in-plane circular photogalvanic current even under normal incidence. The application of an out-of-plane displacement field further systematically controls the direction and magnitude of the photocurrent. Our observed photocurrent reveals a novel Berry curvature dipole that arises from the nontrivial wavefunctions near the inverted gap edge. These previously unrealized Berry curvature dipole and strong electric field effect are uniquely enabled by the inverted band structure and tilted crystal lattice of monolayer WTe2. Such an electrically switchable Berry curvature dipole opens the door to the observation of a wide range of quantum geometrical phenomena, such as quantum nonlinear Hall, orbital-Edelstein and chiral polaritonic effects.