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I am an associate research scientist and adjunct professor of Physics at Columbia University.
I work in condensed matter theory.
Here you can find information about my research and other academic activities.
Research interests
Disorder and correlations in low-dimensional systems
Spintronics and magnetism
Graphene and other 2D materials, including moirés
Check out my articles in arXiv.
Selected publications
Degradation of phonons in disordered moiré superlattices, Phys. Rev. Lett. 128, 065901 (2022)
Spintronics in graphene and other two-dimensional materials, Rev. Mod. Phys. 92, 021003 (2020)
Spin hydrodynamics in amorphous magnets, Phys. Rev. B 98, 054424 (2018)
Emergent gauge fields from curvature in single layers of transition-metal dichalcogenides, Phys. Rev. Lett. 118, 026801 (2017)
News
Excitonic and magnetic phases in doped WTe2 monolayers: a Hartree-Fock approach, posted in arXiv. This is a collaboration with Guillermo Parra-Martínez (Imdea), Daniel Muñoz-Segovia (Columbia), and Jose Angle Silva-Guillén (Imdea), where we discuss the T=0 phase diagram of this material as a function of Coulomb interaction strength and electron density.
Magnetic injection photocurrents in valley polarized states of twisted bilayer graphene, posted in arXiv. In this collaboration led by Fernando Peñaranda and Fernando de Juan (DIPC), we explore how photocurrents may help to discriminate between different time-reversal symmetry broken states in magic-angle twisted bilayer graphene as a function of flat-band filling. This is a follow-up of our previous work Intrinsic and extrinsic photogalvanic effects in twisted bilayer graphene, recently published in Physical Review Letters.
Flat and tunable moiré phonons in twisted transition-metal dichalcogenides, published in Physical Review Letters as an Editors' suggestion. In this collaboration with Alejandro Ramos-Alonso (Columbia), Daniel Bennet (Harvard), Benjamin Remez (Yale) and Rafael M. Fernandes (now in Urbana), we found that a vertical electric field can be used to modify the phonon spectrum of moiré patterns formed by noncentrosymmetric materials. The origin of this coupling is the formation of a polarization texture strongly tied to the stacking configuration (sliding ferrolectricity). Phonon flat bands form for realistic values of the electric field.
For undergrad students: There are research opportunities for you. If you are a student at Columbia and you find some of the stuff in this webpage interesting, shoot me an email to ho2273 at columbia.edu.
Research
I am interested in phenomena at the intersection between hard and soft condensed matter physics, particularly in situations where the floppiness in the structure of the material affects the quantum mechanical behavior of electrons. Examples include electronic membranes such as graphene and other 2D materials, and more recently, the quasi-periodic structures that they form when stacked on top of each other. I am also interested in spin dynamics in solid state, from fundamental phenomena to applications in spintronics.
In the sidebars you can find more information about past and current research projects.
Teaching
I am teaching Statistical Mechanics (GR6036) in the fall. Lectures are on Tuesday and Thursday from 10:10am to 11:25am. Office hours are on Friday from 3:00pm to 5:00pm. My office is 919 CEPSR.
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