Adonai Cruz

I am a theoretical and computational physicist with interest in spin-dependent phenomena in solid-state systems. Currently I am working in the group of Prof. Michael Flatté at the University of Iowa.

I have experience in modeling electronic structure and spin-dependent transport in semiconductors and device structures. Skilled in C++ and Python programming for scientific calculations and visualization including for density-matrix evolutions and electric-field-induced dynamics. Also acquired extensive experience during my PhD studies in ab initio calculations with commercial and open-source codes and developed C++/MPI research codes. These days I primarily work in C++ and Python, but I have coded in Julia, Fortran, Mathematica and Javascript in the past as well.

I worked at QuantCAD as Principal Investigar (PI) in two NASA SBIR projects and one DARPA award where I performed computational simulations of spin-dependent phenomena in semiconductors for quantum sensing applications and managed projects involving multiple teams from both industry and academia. I helped to write technical proposals for DOE, NSF, DARPA and NASA. I developed Lindblad density-matrix solvers on top of QuTiP for simulating the dynamics of open quantum system and incorporated Monte Carlo device simulation and calculations of spin dephasing and decoherence of NV-center sensors varying environmental conditions

selected publications

Dissipationless Circulating Currents and Fringe Magnetic Fields Near a Single Spin Embedded in a Two-Dimensional Electron Gas

A.R. Da Cruz , and M.E. Flatté

Physical Review Letters, Aug 2023

Abs Bib HTML

Theoretical calculations predict the anisotropic dissipationless circulating current induced by a spin defect in a two-dimensional electron gas. The shape and spatial extent of these dissipationless circulating currents depend dramatically on the relative strengths of spin-orbit fields with differing spatial symmetry, offering the potential to use an electric gate to manipulate nanoscale magnetic fields and couple magnetic defects. The spatial structure of the magnetic field produced by this current is calculated and provides a direct way to measure the spin-orbit fields of the host, as well as the defect spin orientation, eg, through scanning nanoscale magnetometry.
@article{dacruzDissipationlessCirculatingCurrents2023, title = {Dissipationless {{Circulating Currents}} and {{Fringe Magnetic Fields Near}} a {{Single Spin Embedded}} in a {{Two-Dimensional Electron Gas}}}, author = {Da Cruz, A.R. and Flatt{\'e}, M.E.}, year = {2023}, month = aug, journal = {Physical Review Letters}, volume = {131}, number = {8}, pages = {086301}, issn = {0031-9007, 1079-7114}, doi = {10.1103/PhysRevLett.131.086301}, urldate = {2024-01-18}, langid = {english}, }
Probing the Local Electronic Structure of Isovalent Bi Atoms in InP

C.M. Krammel , A.R. Da Cruz , M.E Flatté , and 7 more authors

Physical Review B, Aug 2020

Abs Bib

Cross-sectional scanning tunneling microscopy (X-STM) is used to experimentally study the influence of isovalent Bi atoms on the electronic structure of InP. We map the spatial pattern of the Bi impurity state, which originates from Bi atoms down to the sixth layer below the surface, in topographic, filled-state X-STM images on the natural {110} cleavage planes. The Bi impurity state has a highly anisotropic bowtielike structure and extends over several lattice sites. These Bi-induced charge redistributions extend along the 110 directions, which define the bowtielike structures we observe. Local tight-binding calculations reproduce the experimentally observed spatial structure of the Bi impurity state. In addition, the influence of the Bi atoms on the electronic structure is investigated in scanning tunneling spectroscopy measurements. These measurements show that Bi induces a resonant state in the valence band, which \ldots
@article{krammel2020probing, title = {Probing the Local Electronic Structure of Isovalent {{Bi}} Atoms in {{InP}}}, author = {Krammel, C.M. and Da Cruz, A.R. and Flatt{\'e}, M.E and Roy, M. and Maksym, P.A. and Zhang, L.Y. and Wang, K. and Li, Y.Y and Wang, S.M. and Koenraad, P.M}, year = {2020}, journal = {Physical Review B}, volume = {101}, number = {2}, pages = {024113}, publisher = {{American Physical Society}}, }
High-Frequency Sheet Conductance of Nanolayered WS2 Crystals for Two-Dimensional Nanodevices

S.E. Ter Huurne , A.R. Da Cruz , N. Van Hoof , and 5 more authors

ACS Applied Nano Materials, Aug 2022

Abs Bib

Time-resolved terahertz (THz) spectroscopy is a powerful technique for the determination of charge transport properties in photoexcited semiconductors. However, the relatively long wavelengths of THz radiation and the diffraction limit imposed by optical imaging systems reduce the applicability of THz spectroscopy to large samples with dimensions in the millimeter to centimeter range. Exploiting THz near-field spectroscopy, we present the first time-resolved THz measurements on a single exfoliated 2D nanolayered crystal of a transition metal dichalcogenide (WS2). The high spatial resolution of THz near-field spectroscopy enables mapping of the sheet conductance for an increasing number of atomic layers. The single-crystalline structure of the nanolayered crystal allows for the direct observation of low-energy phonon modes, which are present in all thicknesses, coupling with free carriers. Density functional theory \ldots
@article{ter2022high, title = {High-Frequency Sheet Conductance of Nanolayered {{WS2}} Crystals for Two-Dimensional Nanodevices}, author = {Ter Huurne, S.E. and Da Cruz, A.R. and Van Hoof, N. and Godiksen, R. H. and Elrafei, S.A. and Curto, A. G. and Flatt{\'e}, M. E. and Rivas, J. G.}, year = {2022}, journal = {ACS Applied Nano Materials}, volume = {5}, number = {10}, pages = {15557--15562}, publisher = {{American Chemical Society}}, }