arXiv subjects

M. A. Huber

Publications and source records attributed to M. A. Huber.

3 recordsLinked to original sources

arXiv2026

Sign-resolved nanoscale readout and control of hidden antiferromagnetic spin order

Antiferromagnetic memories promise ultrafast, stray-field-free information storage. Yet perfect magnetic compensation conceals the information carrier itself: the sign of the N\'eel vector distinguishing two time-reversed states. Moreover, in future dense memories, the local polarity of N\'eel domains would need to be read out on the nanoscale. We make this hidden polarity visible in a fully-compensated, high-N\'eel-temperature, PT-symmetric antiferromagnet by driving interband electric-dipole transitions by mid-infrared near-fields confined at a scanning probe. The excitation generates a N\'eel-order-dependent quantum-metric photocurrent, a Hall-like signal reversing with N\'eel order, which we term the optical nonlinear anomalous Hall effect. This optically induced electrical readout maps opposite N\'eel polarities with sub-100-nm resolution at room temperature and, combined with spin-orbit-torque writing, reveals N\'eel-texture polarization and reversible domain-wall motion, establishing electrical-write/optoelectronic-read antiferromagnetic functionality.

cond-mat.mtrl-sci↗

arXiv2016

Ultrafast mid-infrared nanoscopy of strained vanadium dioxide nanobeams

Long regarded as a model system for studying insulator-to-metal phase transitions, the correlated electron material vanadium dioxide (VO$_2$) is now finding novel uses in device applications. Two of its most appealing aspects are its accessible transition temperature ($\sim$341 K) and its rich phase diagram. Strain can be used to selectively stabilize different VO$_2$ insulating phases by tuning the competition between electron and lattice degrees of freedom. It can even break the mesoscopic spatial symmetry of the transition, leading to a quasi-periodic ordering of insulating and metallic nanodomains. Nanostructuring of strained VO$_2$ could potentially yield unique components for future devices. However, the most spectacular property of VO$_2$ - its ultrafast transition - has not yet been studied on the length scale of its phase heterogeneity. Here, we use ultrafast near-field microscopy in the mid-infrared to study individual, strained VO$_2$ nanobeams on the 10 nm scale. We reveal a previously unseen correlation between the local steady-state switching susceptibility and the local ultrafast response to below-threshold photoexcitation. These results suggest that it may be possible to tailor the local photo-response of VO$_2$ using strain and thereby realize new types of ultrafast nano-optical devices.

cond-mat.mes-hall↗

arXiv2016

Ultrafast single-nanowire multi-terahertz spectroscopy with sub-cycle temporal resolution

Phase-locked ultrashort pulses in the rich terahertz (THz) spectral range have provided key insights into phenomena as diverse as quantum confinement, first-order phase transitions, high-temperature superconductivity, and carrier transport in nanomaterials. Ultrabroadband electro-optic sampling of few-cycle field transients can even reveal novel dynamics that occur faster than a single oscillation cycle of light. However, conventional THz spectroscopy is intrinsically restricted to ensemble measurements by the diffraction limit. As a result, it measures dielectric functions averaged over the size, structure, orientation and density of nanoparticles, nanocrystals or nanodomains. Here, we extend ultrabroadband time-resolved THz spectroscopy (20 - 50 THz) to the sub-nanoparticle scale (10 nm) by combining sub-cycle, field-resolved detection (10 fs) with scattering-type near-field scanning optical microscopy (s-NSOM). We trace the time-dependent dielectric function at the surface of a single photoexcited InAs nanowire in all three spatial dimensions and reveal the ultrafast ($<$50 fs) formation of a local carrier depletion layer.

cond-mat.mes-hall↗