arXiv subjects

M. Straub

Publications and source records attributed to M. Straub.

5 recordsLinked to original sources

arXiv2026

Electron-phonon coupling across the TMD/hBN van der Waals interface

Many-body interactions can couple electronic states in one layer with collective excitations in the adjacent layer, providing a route to tailor properties of heterostructures. However, detecting and quantifying interlayer many-body interactions proved a major challenge. Here, we demonstrate that quasiparticles in monolayer transition metal dichalcogenides (TMDs) are dressed by a remote cloud of phonons in the adjacent hexagonal boron nitride slab. Using angle resolved photoemission, we identify replica bands in the TMDs which are a clear fingerprint of long-range electron-phonon interaction. We develop a modified Fr\"ohlich model that shows semi-quantitative agreement with the experimental spectral functions. Our analysis shows that remote electron-phonon coupling is a generic property of interfaces with hBN. This has implications for electron mobilities in 2D materials, for superconductivity and possibly for moir\'e correlated phases.

cond-mat.mtrl-sci↗

arXiv2025

Non-Fermi liquid quasiparticles in strain-tuned Sr2RuO4

Interacting electrons can form metallic states beyond the Fermi liquid paradigm, a conceptual frontier of many-body physics mainly explored via bulk thermodynamics and transport. In contrast, the microscopics of anomalous single-particle excitations underlying non-Fermi liquid properties have largely remained in the dark. Here we spectroscopically map such quantum-critical excitations in Sr$_2$RuO$_4$ under uniaxial pressure, an experimental challenge overcome by technical advances combining focused ion beam micro-milling with laser angle resolved photoemission. We show that quasiparticle excitations acquire a non-Fermi liquid scattering rate near the critical point but remain remarkably robust throughout the transition. These experiments serve as a benchmark for the theory of anomalous metals and settle the long-standing question if quantum-critical systems host quasiparticle excitations.

cond-mat.str-el↗

arXiv2024

Fermi surface and pseudogap in highly doped Sr$_{2}$IrO$_{4}$

The fate of the Fermi surface in bulk electron-doped Sr$_{2}$IrO$_{4}$ remains elusive, as does the origin and extension of its pseudogap phase. Here, we use high-resolution angle-resolved photoelectron spectroscopy (ARPES) to investigate the electronic structure of Sr$_{2-x}$La$_{x}$IrO$_{4}$ up to $x=0.2$, a factor of two higher than in previous work. We find that the antinodal pseudogap persists up to the highest doping level, and thus beyond the sharp increase in Hall carrier density to $\simeq 1+x$ recently observed above $x^{*}\simeq 0.16$ [Y.-T. Hsu et al., Nature Physics 20, 1593 (2024)]. This suggests that doped iridates host a unique phase of matter in which a large Hall density coexists with an anisotropic pseudogap, breaking up the Fermi surface into disconnected arcs. The temperature boundary of the pseudogap is $T^{*}\simeq 200$ K for $x=0.2$, comparable to cuprates and to the energy scale of short range antiferromagnetic correlations in cuprates and iridates.

cond-mat.str-el↗

arXiv2024

Nature of metallic and insulating domains in the CDW system 1T-TaSe2

We study the electronic structure of bulk 1T-TaSe$_2$ in the charge density wave phase at low temperature. Our spatially and angle resolved photoemission (ARPES) data show insulating areas coexisting with metallic regions characterized by a chiral Fermi surface and moderately correlated quasiparticle bands. Additionally, high-resolution laser ARPES reveals variations in the metallic regions, with series of low-energy states, whose energy, number and dispersion can be explained by the formation of quantum well states of different thicknesses. Dynamical mean field theory calculations show that the observed rich behaviour can be rationalized by assuming occasional stacking faults of the charge density wave. Our results indicate that the diverse electronic phenomena reported previously in 1T-TaSe$_2$ are dictated by the stacking arrangement and the resulting quantum size effects while correlation effects play a secondary role.

cond-mat.str-el↗

arXiv2023

The fate of quasiparticles at high-temperature

We study the temperature evolution of quasiparticles in the correlated metal Sr$_2$RuO$_4$. Our angle resolved photoemission data show that quasiparticles persist up to temperatures above 200~K, far beyond the Fermi liquid regime. Extracting the quasiparticle self-energy we demonstrate that the quasiparticle residue $Z$ increases with increasing temperature. Quasiparticles eventually disappear on approaching the bad metal state of Sr$_2$RuO$_4$ not by losing weight but via excessive broadening from super-Planckian scattering. We further show that the Fermi surface of Sr$_2$RuO$_4$ - defined as the loci where the spectral function peaks - deflates with increasing temperature. These findings are in semi-quantitative agreement with dynamical mean field theory calculations.

cond-mat.str-el↗