2022 New's Items

Density of states prediction for materials discovery via contrastive learning from probabilistic embeddings

Kong S
Ricci F
Guevarra D
Neaton JB
Gomes CP
Gregoire JM
2022

Machine learning for materials discovery has largely focused on predicting an individual scalar rather than multiple related properties, where spectral properties are an important example. Fundamental spectral properties include the phonon density of states (phDOS) and the electronic density of states (eDOS), which individually or collectively are the origins of a breadth of materials observables and functions. Building upon the success of graph attention networks for encoding crystalline materials, we introduce a probabilistic embedding generator specifically tailored to the prediction of...

Current-enabled optical conductivity of superconductors

Papaj M
Moore JE
2022

In most superconductors, optical excitations require impurity scattering or the presence of multiple bands. This is because in clean single-band superconductors, the combination of particle-hole and inversion symmetries prevents momentum-conserving transitions. In this Letter we show how the flow of supercurrent can lead to new contributions to optical conductivity. As the supercurrent breaks inversion symmetry, transitions across the superconducting gap become allowed even in clean superconductors and dominate over impurity-induced contributions for energies comparable to the gap...

Quantum criticality using a superconducting quantum processor

Dupont M
Moore JE
2022

Quantum criticality emerges from the collective behavior of many interacting quantum particles, often at the transition between different phases of matter. It is one of the cornerstones of condensed matter physics, which we access on noisy intermediate-scale (NISQ) quantum devices by leveraging a dynamically driven phenomenon. We probe the critical properties of the one-dimensional quantum Ising model on a programmable superconducting quantum chip via a Kibble-Zurek process, obtain scaling laws, and estimate critical exponents despite inherent sources of errors on the hardware. In...

SWAP Gate between a Majorana Qubit and a Parity-Protected Superconducting Qubit

Chirolli L
Yao NY
Moore JE
2022

High fidelity quantum information processing requires a combination of fast gates and long-lived quantum memories. In this Letter, we propose a hybrid architecture, where a parity-protected superconducting qubit is directly coupled to a Majorana qubit, which plays the role of a quantum memory. The superconducting qubit is based upon a π-periodic Josephson junction realized with gate-tunable semiconducting wires, where the tunneling of individual Cooper pairs is suppressed. One of the wires additionally...

Identifying Majorana vortex modes via nonlocal transport

Sbierski B
Geier M
Li AP
Brahlek M
Moore RG
Moore JE
2022

The combination of two-dimensional Dirac surface states with s-wave superconductivity is expected to generate localized topological Majorana zero modes in vortex cores. Putative experimental signatures of these modes have been reported for heterostructures of proximitized topological insulators, iron-based superconductors or certain transition metal dichalcogenides. Despite these efforts, the Majorana nature of the observed excitation is still under debate. We propose to identify the presence of Majorana...

Entanglement perspective on the quantum approximate optimization algorithm

Dupont M
Didier N
Hodson MJ
Moore JE
Reagor MJ
2022

Many quantum algorithms seek to output a specific bitstring solving the problem of interest—or a few if the solution is degenerate. It is the case for the quantum approximate optimization algorithm (QAOA) in the limit of large circuit depth, which aims to solve quadratic unconstrained binary optimization problems. Hence, the expected final state for these algorithms is either a product state or a low-entangled superposition involving a few bitstrings. What happens in between the initial N-qubit product...

Observation of a phase transition within the domain walls of ferromagnetic Co3Sn2S2

Lee C
Vir P
Manna K
Shekhar C
Moore JE
Kastner MA
Felser C
Orenstein J
2022

The ferromagnetic phase of Co3Sn2S2 is widely considered to be a topological Weyl semimetal, with evidence for momentum-space monopoles of Berry curvature from transport and spectroscopic probes. As the bandstructure is highly sensitive to the magnetic order, attention has focused on anomalies in magnetization, susceptibility and transport measurements that are seen well below the Curie temperature, leading to speculation that a “hidden” phase coexists with ferromagnetism. Here we report spatially-resolved...

Imaging gate-tunable Tomonaga–Luttinger liquids in 1H-MoSe2 mirror twin boundaries

Zhu T
Ruan W
Wang YQ
Zhang G
Wang F
Moore JE
Crommie MF
2022

One-dimensional electron systems exhibit fundamentally different properties than higher-dimensional systems. For example, electron–electron interactions in one-dimensional electron systems have been predicted to induce Tomonaga–Luttinger liquid behaviour. Naturally occurring grain boundaries in single-layer transition metal dichalcogenides exhibit one-dimensional conducting channels that have been proposed to host Tomonaga–Luttinger liquids, but charge density wave physics has also been suggested to explain their behaviour. Clear identification of the electronic ground state of this...

Thermal Probes of Phonon-Coupled Kitaev Spin Liquids: From Accurate Extraction of Quantized Edge Transport to Anyon Interferometry

Klocke K
Moore JE
Alicea J
Halász GB
2022

Recent theoretical studies inspired by experiments on the Kitaev magnet α−RuCl3 highlight the nontrivial impact of phonons on the thermal Hall conductivity of chiral topological phases. Here, we introduce mixed mesoscopic-macroscopic devices that allow refined thermal-transport probes of non-Abelian spin liquids with Ising topological order...

Direct geometric probe of singularities in band structure

Brown CD
Chang SW
Schwarz MN
Leung TH
Kozii V
Avdoshkin A
Moore JE
Stamper-Kurn D
2022

A quantum system’s energy landscape may have points where multiple energy surfaces are degenerate and that exhibit singular geometry of the wave function manifold, with major consequences for the system’s properties. Ultracold atoms in optical lattices have been used to indirectly characterize such points in the band structure. We measured the non-Abelian transformation produced by transport directly through the singularities. We accelerated atoms along a quasi-momentum trajectory that enters, turns, and then exits the singularities at linear and quadratic band-touching points of a...