15 research outputs found
Frustrated Magnetic Cycloidal Structure and Emergent Potts Nematicity in CaMnP
We report neutron-diffraction results on single-crystal CaMnP
containing corrugated Mn honeycomb layers and determine its ground-state
magnetic structure. The diffraction patterns consist of prominent (1/6, 1/6,
) reciprocal lattice unit (r.l.u.; = integer) magnetic Bragg
reflections, whose temperature-dependent intensities are consistent with a
first-order antiferromagnetic phase transition at the N\'eel temperature
K. Our analysis of the diffraction patterns reveals an
in-plane magnetic unit cell with ordered spins that in the
principal-axis directions rotate by 60-degree steps between nearest neighbors
on each sublattice that forms the honeycomb structure, consistent with the
magnetic space group. We find that a few other magnetic subgroup
symmetries (, , ) of the
paramagnetic crystal symmetry are consistent with the
observed diffraction pattern. We relate our findings to frustrated
-- Heisenberg honeycomb antiferromagnets with single-ion
anisotropy and the emergence of Potts nematicit
Recommended from our members
Discovery of a weak topological insulating state and van Hove singularity in triclinic RhBi 2
Abstract: Time reversal symmetric (TRS) invariant topological insulators (TIs) fullfil a paradigmatic role in the field of topological materials, standing at the origin of its development. Apart from TRS protected strong TIs, it was realized early on that more confounding weak topological insulators (WTI) exist. WTIs depend on translational symmetry and exhibit topological surface states only in certain directions making it significantly more difficult to match the experimental success of strong TIs. We here report on the discovery of a WTI state in RhBi2 that belongs to the optimal space group P1¯, which is the only space group where symmetry indicated eigenvalues enumerate all possible invariants due to absence of additional constraining crystalline symmetries. Our ARPES, DFT calculations, and effective model reveal topological surface states with saddle points that are located in the vicinity of a Dirac point resulting in a van Hove singularity (VHS) along the (100) direction close to the Fermi energy (EF). Due to the combination of exotic features, this material offers great potential as a material platform for novel quantum effects
Quantum metric nonlinear Hall effect in a topological antiferromagnetic heterostructure
Quantum geometry - the geometry of electron Bloch wavefunctions - is central
to modern condensed matter physics. Due to the quantum nature, quantum geometry
has two parts, the real part quantum metric and the imaginary part Berry
curvature. The studies of Berry curvature have led to countless breakthroughs,
ranging from the quantum Hall effect in 2DEGs to the anomalous Hall effect
(AHE) in ferromagnets. However, in contrast to Berry curvature, the quantum
metric has rarely been explored. Here, we report a new nonlinear Hall effect
induced by quantum metric by interfacing even-layered MnBi2Te4 (a PT-symmetric
antiferromagnet (AFM)) with black phosphorus. This novel nonlinear Hall effect
switches direction upon reversing the AFM spins and exhibits distinct scaling
that suggests a non-dissipative nature. Like the AHE brought Berry curvature
under the spotlight, our results open the door to discovering quantum metric
responses. Moreover, we demonstrate that the AFM can harvest wireless
electromagnetic energy via the new nonlinear Hall effect, therefore enabling
intriguing applications that bridges nonlinear electronics with AFM
spintronics.Comment: 19 pages, 4 figures and a Supplementary Materials with 66 pages, 4
figures and 3 tables. Originally submitted to Science on Oct. 5, 202
Quantum dynamics simulations beyond the coherence time on NISQ hardware by variational Trotter compression
We demonstrate a post-quench dynamics simulation of a Heisenberg model on
present-day IBM quantum hardware that extends beyond the coherence time of the
device. This is achieved using a hybrid quantum-classical algorithm that
propagates a state using Trotter evolution and then performs a classical
optimization that effectively compresses the time-evolved state into a
variational form. When iterated, this procedure enables simulations to
arbitrary times with an error controlled by the compression fidelity and a
fixed Trotter step size. We show how to measure the required cost function, the
overlap between the time-evolved and variational states, on present-day
hardware, making use of several error mitigation methods. In addition to
carrying out simulations on real hardware, we investigate the performance and
scaling behavior of the algorithm with noiseless and noisy classical
simulations. We find the main bottleneck in going to larger system sizes to be
the difficulty of carrying out the optimization of the noisy cost function.Comment: 11 pages, 9 figure