Dr. rer. nat., Max-Planck-Institut für Chemische Physik fester Stoffe, Dresden (2019)
Master of Science, Indian Institute of Technology (IIT), Kharagpur, Physics (2013)
Bachelor of Science, St. Xavier's College, Kolkata, Physics (2011)
Kathryn Moler, Postdoctoral Faculty Sponsor
- Unconventional magneto-transport in ultrapure PdCoO2 and PtCoO2 NPJ QUANTUM MATERIALS 2018; 3
Uniaxial pressure control of competing orders in a high-temperature superconductor
2018; 362 (6418): 1040-+
Cuprates exhibit antiferromagnetic, charge density wave (CDW), and high-temperature superconducting ground states that can be tuned by means of doping and external magnetic fields. However, disorder generated by these tuning methods complicates the interpretation of such experiments. Here, we report a high-resolution inelastic x-ray scattering study of the high-temperature superconductor YBa2Cu3O6.67 under uniaxial stress, and we show that a three-dimensional long-range-ordered CDW state can be induced through pressure along the a axis, in the absence of magnetic fields. A pronounced softening of an optical phonon mode is associated with the CDW transition. The amplitude of the CDW is suppressed below the superconducting transition temperature, indicating competition with superconductivity. The results provide insights into the normal-state properties of cuprates and illustrate the potential of uniaxial-pressure control of competing orders in quantum materials.
View details for DOI 10.1126/science.aat4708
View details for Web of Science ID 000451609000042
View details for PubMedID 30498124
Hydrodynamic Electron Flow and Hall Viscosity
PHYSICAL REVIEW LETTERS
2017; 118 (22): 226601
In metallic samples of small enough size and sufficiently strong momentum-conserving scattering, the viscosity of the electron gas can become the dominant process governing transport. In this regime, momentum is a long-lived quantity whose evolution is described by an emergent hydrodynamical theory. Furthermore, breaking time-reversal symmetry leads to the appearance of an odd component to the viscosity called the Hall viscosity, which has attracted considerable attention recently due to its quantized nature in gapped systems but still eludes experimental confirmation. Based on microscopic calculations, we discuss how to measure the effects of both the even and odd components of the viscosity using hydrodynamic electronic transport in mesoscopic samples under applied magnetic fields.
View details for DOI 10.1103/PhysRevLett.118.226601
View details for Web of Science ID 000402681500005
View details for PubMedID 28621998
Evidence for hydrodynamic electron flow in PdCoO2
2016; 351 (6277): 1061–64
Electron transport is conventionally determined by the momentum-relaxing scattering of electrons by the host solid and its excitations. Hydrodynamic fluid flow through channels, in contrast, is determined partly by the viscosity of the fluid, which is governed by momentum-conserving internal collisions. A long-standing question in the physics of solids has been whether the viscosity of the electron fluid plays an observable role in determining the resistance. We report experimental evidence that the resistance of restricted channels of the ultrapure two-dimensional metal palladium cobaltate (PdCoO2) has a large viscous contribution. Comparison with theory allows an estimate of the electronic viscosity in the range between 6 × 10(-3) kg m(-1) s(-1) and 3 × 10(-4) kg m(-1) s(-1), versus 1 × 10(-3) kg m(-1) s(-1) for water at room temperature.
View details for DOI 10.1126/science.aac8385
View details for Web of Science ID 000371597500038
View details for PubMedID 26912359
Nearly free electrons in a 5d delafossite oxide metal
2015; 1 (9): e1500692
Understanding the role of electron correlations in strong spin-orbit transition-metal oxides is key to the realization of numerous exotic phases including spin-orbit-assisted Mott insulators, correlated topological solids, and prospective new high-temperature superconductors. To date, most attention has been focused on the 5d iridium-based oxides. We instead consider the Pt-based delafossite oxide PtCoO2. Our transport measurements, performed on single-crystal samples etched to well-defined geometries using focused ion beam techniques, yield a room temperature resistivity of only 2.1 microhm·cm (μΩ-cm), establishing PtCoO2 as the most conductive oxide known. From angle-resolved photoemission and density functional theory, we show that the underlying Fermi surface is a single cylinder of nearly hexagonal cross-section, with very weak dispersion along k z . Despite being predominantly composed of d-orbital character, the conduction band is remarkably steep, with an average effective mass of only 1.14m e. Moreover, the sharp spectral features observed in photoemission remain well defined with little additional broadening for more than 500 meV below E F, pointing to suppressed electron-electron scattering. Together, our findings establish PtCoO2 as a model nearly-free-electron system in a 5d delafossite transition-metal oxide.
View details for DOI 10.1126/sciadv.1500692
View details for Web of Science ID 000216598200034
View details for PubMedID 26601308
View details for PubMedCentralID PMC4646822