A5035088271- Physics of Superconductivity and Magnetism
- Quantum and electron transport phenomena
- Quantum, superfluid, helium dynamics
- Rare-earth and actinide compounds
- Advanced Condensed Matter Physics
- Magnetic and transport properties of perovskites and related materials
- Advanced Chemical Physics Studies
- Surface and Thin Film Phenomena
- Iron-based superconductors research
- Theoretical and Computational Physics
- Organic and Molecular Conductors Research
- Semiconductor Quantum Structures and Devices
- Black Holes and Theoretical Physics
- 2D Materials and Applications
- Quantum Chromodynamics and Particle Interactions
- Electron and X-Ray Spectroscopy Techniques
- Diamond and Carbon-based Materials Research
- Quantum many-body systems
- Topological Materials and Phenomena
- High-pressure geophysics and materials
- Electronic and Structural Properties of Oxides
- Cold Atom Physics and Bose-Einstein Condensates
- Thermal Radiation and Cooling Technologies
- Particle physics theoretical and experimental studies
- Superconductivity in MgB2 and Alloys
University of Wisconsin–Madison
2022-2025
Harvard University
2020-2024
Stanford University
2016-2023
University of Geneva
2020
SLAC National Accelerator Laboratory
2016
Perimeter Institute
2014
Strange metals-ubiquitous in correlated quantum materials-transport electrical charge at low temperatures but not by the individual electronic quasiparticle excitations, which carry ordinary metals. In this work, we consider two-dimensional metals of fermions coupled to critical scalars, latter representing order parameters or fractionalized particles. We show that (T), such generically exhibit strange metal behavior with a T-linear resistivity arising from spatially random fluctuations...
Characterizing the interplay between non-Fermi-liquid physics and superconductivity is an important open problem in condensed matter physics. From a theoretical standpoint, challenge stems from difficulty identifying controlled models where these phenomena can be simultaneously treated on equal footing. Here, authors propose new model of strongly interacting electrons phonons, close analogy with well-known Sachdev-Ye-Kitaev model, and, via exact solution, explore how emerge quantum critical...
The superconducting (SC) and charge-density-wave (CDW) susceptibilities of the two dimensional Holstein model are computed using determinant quantum Monte Carlo (DQMC), compared with results Migdal-Eliashberg (ME) approach. We access temperatures as low 25 times less than Fermi energy, $E_F$, which still above SC transition. find that susceptibility at $T$ agrees quantitatively ME theory up to a dimensionless electron-phonon coupling $\lambda_0 \approx 0.4$ but deviates dramatically for...
We describe the large $N$ saddle point, and structure of fluctuations about a theory containing sharp, critical Fermi surface in two spatial dimensions. The describes onset Ising order liquid, closely related theories apply to other cases with surfaces. employ random couplings flavor space between fermions bosonic parameter, but there is no randomness: consequently, $G$-$\Sigma$ path integral expressed terms fields bilocal spacetime. exponents saddle-point are same as well-studied non-random...
A Fermi surface coupled to a scalar field can be described in $1/N$ expansion by choosing the fermion-scalar Yukawa coupling random $N$-dimensional flavor space, but invariant under translations. We compute conductivity of such theory two spatial dimensions for critical scalar. find Drude contribution, and verify that proposed $1/\omega^{2/3}$ contribution optical at frequency $\omega$ has vanishing co-efficient convex surface. also describe influence impurity scattering fermions, while self...
Scattering experiments have revolutionized our understanding of nature. Examples include the discovery nucleus, crystallography, and double helix structure DNA. techniques differ by type particles used, interaction these with target materials range wavelengths used. Here, we demonstrate a new 2-dimensional table-top scattering platform for exploring magnetic properties on mesoscopic length scales. Long lived, coherent magnonic excitations are generated in thin film YIG scattered off...
We use the numerical conformal bootstrap in two dimensions to search for finite, closed sub-algebras of operator product expansion (OPE), without assuming unitarity. find minimal models as special cases, well additional lines solutions that can be understood Coulomb gas formalism. All we contain vacuum algebra are cases where external operators equation degenerate operators, and argue this follows analytically from expressions arXiv:1202.4698 crossing matrices Virasoro blocks. Our analysis...
Abstract It is notoriously difficult to make quantitative theoretical predictions of the superconducting transition temperature, T c , either from first-principles or even a knowledge normal state properties. Ultimately, this reflects fact that energy scales involved in are extremely small natural units, and depends exponentially on subtle interplay between different interactions so uncertainties microscopic processes can lead order one effects . However, some circumstances, it may be...
Strongly correlated metals often display anomalous transport, including T-linear resistivity above the Mott-Ioffe-Regel limit. We introduce a tractable microscopic model for bad metals, by restoring in well-known Hubbard model-with hopping t and on-site repulsion U-a "screened Coulomb" interaction between charge densities that decays exponentially with spatial separation. This lifts extensive degeneracy spectrum of t=0 model, allowing us to fully characterize small electric, thermal,...
Thermodynamic properties of the square-lattice Holstein model electron-phonon problem with phonon frequencies small compared to bare Fermi energy are obtained using Monte Carlo methods, a strong-coupling (bipolaronic) expansion, and weak-coupling Migdal-Eliashberg approach. Already at elevated temperatures where charge-density wave (CDW) superconducting (SC) correlations very short range, crossover occurs as function increasing coupling, ${\ensuremath{\lambda}}_{0}$, from normal metallic...
A single-spin qubit placed near the surface of a conductor acquires an additional contribution to its 1/T1 relaxation rate due magnetic noise created by electric current fluctuations in material. We analyze this technique as wireless probe superconductivity atomically thin two-dimensional materials. At temperatures T≲Tc, dominant is transverse arising from quasiparticle excitations. demonstrate that method enables detection metal-to-superconductor transitions, well investigation symmetry...
We propose nanoscale magnetometry via isolated single-spin qubits as a probe of superconductivity in two-dimensional materials. characterize the magnetic field noise at qubit location, arising from current and spin fluctuations sample leading to measurable polarization decay qubit. show that due transverse studied function temperature sample-probe distance can be used extract useful information about transition superconducting phase pairing symmetry superconductor. Surprisingly, low...
Perturbative considerations account for the properties of conventional metals, including range temperatures where transport scattering rate is $1/\tau_\text{tr} = 2\pi \lambda T$, $\lambda$ a dimensionless strength electron-phonon coupling. The fact that measured values satisfy $\lambda \lesssim 1$ has been noted in context possible "Planckian" bound on transport. However, since quasi-elastic this regime, no such Planckian can be relevant. We present and analyze Monte Carlo results Holstein...
The electron-phonon $(e\text{\ensuremath{-}}\mathrm{ph})$ interaction remains of great interest in condensed matter physics and plays a vital role realizing superconductors, charge density waves (CDW), polarons. We study the two-dimensional Holstein model for $e\text{\ensuremath{-}}\mathrm{ph}$ coupling using determinant quantum Monte Carlo across wide range its phase diagram as function temperature, electron density, dimensionless strength, adiabatic ratio phonon frequency to Fermi energy....
Resonant x-ray scattering measurements reveal the existence of charge ordering in high-temperature cuprate superconductor, La${}_{2\ensuremath{-}x}$Sr${}_{x}$CuO${}_{4}$, well beyond expected levels doping concentrations.
We study the quantum dynamics of interstitials and vacancies in a two-dimensional Wigner crystal (WC) using semiclassical instanton method that is asymptotically exact at low density, i.e., ${r}_{s}\ensuremath{\rightarrow}\ensuremath{\infty}$ limit. The these point defects mediates magnetism with much higher-energy scales than exchange energies pure WC. Via diagonalization derived effective Hamiltonians single-defect sectors, we find dynamical corrections to defect energies. resulting...
We propose local electromagnetic noise spectroscopy as a versatile and noninvasive tool to study Wigner crystal phases of strongly interacting two-dimensional electronic systems. In-plane imaging the is predicted enable single-site resolution electron when sample-probe distance less than interelectron separation. At larger distances, encodes information about low-energy phonons, including dispersion transverse shear mode, pinning resonance due disorder, optical modes emerging, for instance,...
The two-dimensional Yukawa-Sachdev-Ye-Kitaev (2D-YSYK) model provides a universal theory of quantum phase transitions in metals the presence quenched random spatial fluctuations local position critical point. It has Fermi surface coupled to scalar field by spatially Yukawa interactions. We present full numerical solutions self-consistent disorder averaged analysis 2D-YSYK both normal and superconducting states, obtaining electronic spectral functions, frequency-dependent conductivity,...
We report on the properties of two-dimensional electron gas in a dual-gate geometry, using quantum Monte Carlo methods to obtain aspects phase diagram as function density and gate distance. identify critical distance below which Wigner crystal disappears. For larger distances, system undergoes re-entrant transition from liquid at sufficiently low density. also present preliminary evidence for fully polarized ferromagnetic state intermediate distances. The results are compared with simpler...