Publications

Louk Rademaker, Gustavo Alvarez-Suchini, Ken Nakatsukasa, Yan Wang and Steven Johnston

Physical review. B 103 14, 144504 (2021)

We study the effect of combining spin fluctuations and forward scattering electron-phonon (e-ph) coupling on the superconductivity in the FeSe/SrTiO3 system modeled by a phenomenological two-band Hubbard model with long-range {e-ph} interactions. We treat the electron and phonon degrees of freedom…

Louk Rademaker

Physical review. B 104 21, 214204 (2021)

We develop a scaling theory of interaction-induced delocalization of few-particle states in disordered quantum systems. In the absence of interactions, all single-particle states are localized in d

Thomas H.A. van der Reep, Louk Rademaker, Xavier G.A. Le Large, Ruben H. Guis and Tjerk H. Oosterkamp

Physica status solidi. B, Basic research 258 4, 2000567 (2021)

The read-out of a microwave qubit state occurs using an amplification chain that enlarges the quantum state to a signal detectable with a classical measurement apparatus. However, at what point in this process is the quantum state really ‘measured’? In order to investigate whether the `measurement’ …

Louk Rademaker and Marco Gibertini

Physical review materials 5 4, 044201 (2021)

We study free, capped and encapsulated bilayer jacutingaite Pt2HgSe3 from first principles. While the free standing bilayer is a large gap trivial insulator, we find that the encapsulated structure has a small trivial gap due to the competition between sublattice symmetry breaking and…

Yu Saito, Jingyuan Ge, Louk Rademaker, Kenji Watanabe, Takashi Taniguchi, Dmitry Abanin and Andrea F. Young

Nature physics 17 4, 478-481 (2021)

When the twist angle between two layers of graphene is approximately 1.1°, interlayer tunnelling and rotational misalignment conspire to create a pair of flat bands that are known to host various insulating, superconducting and magnetic states when they are partially filled. Most work has focused…

Thomas H.A. van der Reep, Louk Rademaker, Xavier G.A. Le Large, Ruben H. Guis and Tjerk H. Oosterkamp

Physica status solidi. B, Basic research 258 4, 2000567 (2021)

The read-out of a microwave qubit state occurs using an amplification chain that enlarges the quantum state to a signal detectable with a classical measurement apparatus. However, at what point in this process is the quantum state really ‘measured’? In order to investigate whether the `measurement’ …

Simone Lisi, Xiaobo Lu, Tjerk Benschop, Tobias A. de Jong, Petr Stepanov, Jose R. Duran, Florian Margot, Irène Cucchi, Edoardo Cappelli, Andrew Scott Hunter, Anna Tamai, Viktor Kandyba, Alessio Giampietri, Alexei Barinov, Johannes Jobst, Vincent Stalman, Maarten Leeuwenhoek, Kenji Watanabe, Takashi Taniguchi, Louk Rademaker, Sense Jan van der Molen, Milan P. Allan, Dmitri K. Efetov and Felix Baumberger

Nature physics 17 2, 189-193 (2020)

We combine different imaging techniques and angle-resolved photoemission with simultaneous real- and momentum-space resolution (nano-ARPES) to directly map the band dispersion in twisted bilayer graphene devices near charge neutrality. Our experiments reveal large areas with a homogeneous twist…

Louk Rademaker

Preprint (2020)

These lecture notes contain a brief practical introduction to doing density functional theory calculations for crystals using the open source Quantum Espresso software. The level is aimed at graduate students who are studying condensed matter or solid state physics, either theoretical or…

Louk Rademaker, Ivan Protopopov and Dmitry Abanin

Physical review research 2 3, 033150 (2020)

Monolayer graphene placed with a twist on top of AB-stacked bilayer graphene hosts topological flat bands in a wide range of twist angles. The dispersion of these bands and gaps between them can be efficiently controlled by a perpendicular electric field, which induces topological transitions…

Louk Rademaker, Aron Beekman and Jasper van Wezel

Physical review research 2 1, 013304 (2020)

Antiferromagnets and ferromagnets are archetypes of the two distinct (type-A and type-B) ways of spontaneously breaking a continuous symmetry. Although type-B Nambu-Goldstone modes arise in various systems, the ferromagnet was considered pathological due to the stability and symmetry-breaking…

Louk Rademaker and Dmitry Abanin

Physical review letters 125 26, 260405 (2020)

Spin glasses and many-body localization (MBL) are prime examples of ergodicity breaking, yet their physical origin is quite different: the former phase arises due to rugged classical energy landscape, while the latter is a quantum-interference effect. Here, we study quantum dynamics of an isolated…

Aron J. Beekman, Louk Rademaker and Jasper van Wezel

SciPost physics lecture notes, 11 (2019)

Perhaps the most important aspect of symmetry in physics is the idea that a state does not need to have the same symmetries as the theory that describes it. This phenomenon is known as spontaneous symmetry breaking. In these lecture notes, starting from a careful definition of symmetry in physics,…

Louk Rademaker

SciPost physics 7 5, 071 (2019)

I studied the non-equilibrium response of an initial Néel state under time evolution with the Kitaev honeycomb model. With isotropic interactions (Jx=Jy=Jz) the system quickly loses its antiferromagnetic order and crosses over into a steady state valence bond solid, which can be inferred from the…

Miguel Ortuño, Andres M. Somoza and Louk Rademaker

Physical review. B 100 8, 085115 (2019)

Many-body eigenstates beyond the Gaussian approximation can be constructed in terms of local integrals of motion (IOMs), although their actual computation has been, until now, a daunting task. We present a practical computation of IOMs based on displacement transformations and apply it to the…

Louk Rademaker, Dmitry Abanin and Paula Mellado

Physical review. B 100 20, 205114 (2019)

Doping twisted bilayer graphene away from charge neutrality leads to an enormous buildup of charge inhomogeneities within each moiré unit cell. Here, we show, using unbiased real-space self-consistent Hartree calculations on a relaxed lattice, that Coulomb interactions smoothen this charge…

Louk Rademaker

Physical review research 1 3, 032018(R) (2019)

We show that the exact ground state of the Lieb-Mattis Hamiltonian is an equal-weight superposition of all possible classical Néel states, and provide an exact formulation of this superposition in the z-spin basis for both S=1/2 and general S using Schwinger bosons. In general, a superposition of…

Louk Rademaker and Paula Mellado

Physical review. B 98 23, 235158 (2018)

We studied the real-space structure of states in twisted bilayer graphene at the magic angle θ=1.08∘. The flat bands close to charge neutrality are composed of a mix of “ring” and “center” orbitals around the AA stacking region. An effective model with localized orbitals is constructed…

Louk Rademaker, Zohar Nussinov, Leon Balents and Vladimir Dobrosavljević

New journal of physics 20 4, 043026 (2018)

We investigate the structure of metastable states in self-generated Coulomb glasses. In dramatic contrast to disordered electron glasses, we find that these states lack marginal stability. Such absence of marginal stability is reflected by the suppression of the single-particle density of states…

Louk Rademaker and Jan Zaanen

Scientific reports 7 1, 6118 (2017)

The ultimate consequence of quantum many-body physics is that even the air we breathe is governed by strictly unitary time evolution. The reason that we perceive it nonetheless as a completely classical high temperature gas is due to the incapacity of our measurement machines to keep track of the…

Yan Wang, Louk Rademaker, Elbio Dagotto and Steven Johnston

Physical review. B 96 5, 054515 (2017)

The discovery of an enhanced superconducting transition temperature Tc in monolayers of FeSe grown on several oxide substrates has opened a different route to high-Tc superconductivity through interface engineering. One proposal for the origin of the observed enhancement is an electron-phonon…

Louk Rademaker, Valerii M. Vinokur and Alexey Galda

Scientific reports 7 1, 44044 (2017)

We study numerically the voltage-induced breakdown of a Mott insulating phase in a system of charged classical particles with long-range interactions. At half-filling on a square lattice this system exhibits Mott localization in the form of a checkerboard pattern. We find universal scaling behavior …

Louk Rademaker, Miguel Ortuño and Andres M. Somoza

Annalen der Physik 529 7, 1600322 (2017)

We study many-body localization (MBL) and delocalization from the perspective of integrals of motion (IOMs). MBL can be understood phenomenologically through the existence of macroscopically many localized IOMs. However, IOMs exist for all many-body systems, and non-localized IOMs determine…

Y Wang, K Nakatsukasa, Louk Rademaker, T Berlijn and S Johnston

Superconductor science and technology 29 5, 054009 (2016)

Mono- and multilayer FeSe thin films grown on SrTiO3 and BiTiO3 substrates exhibit a greatly enhanced superconductivity over that found in bulk FeSe. A number of proposals have been advanced for the mechanism of this enhancement. One possibility is the introduction of a cross-interface…

Louk Rademaker and Miguel Ortuño

Physical review letters 116 1, 010404 (2016)

Recently, it has been suggested that the Many-Body Localized phase can be characterized by local integrals of motion. Here we introduce a Hilbert space preserving renormalization scheme that iteratively finds such integrals of motion exactly. Our method is based on the consecutive action of a…

Louk Rademaker, Yan Wang, Tom Berlijn and Steve Johnston

New journal of physics 18 2, 022001 (2016)

Louk Rademaker, Arnaud Ralko, Simone Fratini and Vladimir Dobrosavljević

Journal of superconductivity and novel magnetism 29 3, 601-604 (2015)

Louk Rademaker

Physical review. B, Condensed matter and materials physics 92 14, 144419 (2015)

We extend the analytical arguments of Metlitski and Grover (arXiv:1112.5166) to compute the entanglement spectrum and entanglement entropy of coplanar antiferromagnets with SO(3) order parameter symmetry. The low-energy states in the entanglement spectrum exhibit the tower of states structure, as…

Robert-Jan Slager, Louk Rademaker, Jan Zaanen and Leon Balents

Physical review. B, Condensed matter and materials physics 92 8, 085126 (2015)

Samiyeh Mahmoudian, Louk Rademaker, Arnaud Ralko, Simone Fratini and Vladimir Dobrosavljević

Physical review letters 115 2, 025701 (2015)

We show that introducing long-range Coulomb interactions immediately lifts the massive ground state degeneracy induced by geometric frustration for electrons on quarter-filled triangular lattices in the classical limit. Important consequences include the stabilization of a stripe-ordered…

Kai Wu, Louk Rademaker and Jan Zaanen

Physical review applied 2 5 (2014)

Currently, one of the major nanotechnological challenges is to design thermoelectric devices that have a high figure of merit. To that end, we propose to use bilayer excitons. Bilayer exciton systems are shown to have an improved thermopower and an enhanced electric counterflow and thermal…

Louk Rademaker, Jeroen van den Brink, Jan Zaanen and Hans Hilgenkamp

Physical review. B, Condensed matter and materials physics 88 23, 235127 (2013)

We studied the possibility of exciton condensation in Mott insulating bilayers. In these strongly correlated systems an exciton is the bound state of a double occupied and empty site. In the strong coupling limit the exciton acts as a hard-core boson. Its physics are captured by the exciton t-J…

Louk Rademaker, Yohanes Pramudya, Jan Zaanen and Vladimir Dobrosavljević

Physical review. E, Statistical, nonlinear, and soft matter physics 88 3, 032121 (2013)

Usually complex charge ordering phenomena arise due to competing interactions. We have studied how such ordered patterns emerge from the frustration of a long-ranged interaction on a lattice. Using the lattice gas model on a square lattice with fixed particle density, we have identified several…

Louk Rademaker, Steve Johnston, Jan Zaanen and Jeroen van den Brink

Physical review. B, Condensed matter and materials physics 88 23, 235115 (2013)

We studied the possibility of exciton condensation in a strongly correlated bilayer extended Hubbard model using Determinant Quantum Monte Carlo. To model both the onsite repulsion U and the interlayer interaction V we introduced a novel update scheme extending the standard Sherman-Morrison update. …

Louk Rademaker, Jeroen van den Brink, Hans Hilgenkamp and Jan Zaanen

Physical review. B, Condensed matter and materials physics 88 12, 121101 (2013)

We show that an interlayer exciton condensate doped into a strongly correlated Mott insulator exhibits a remarkable enhancement of the bandwidth of the magnetic excitations (triplons). This triplon is visible in the dynamical magnetic susceptibility and can be measured using resonant inelastic…

Louk Rademaker, K. Wu, H. Hilgenkamp and J. Zaanen

Europhysics letters 97 2, 27004 (2012)

Using the self-consistent Born approximation we study the delocalization of interlayer excitons in the bilayer Heisenberg quantum antiferromagnet. Under realistic conditions we find that the coupling between the exciton motion and the spin system is strongly enhanced as compared to the case of a…

Louk Rademaker, Kai Wu and Jan Zaanen

New journal of physics 14 8, 083040 (2012)

We formulated an effective theory for a single interlayer exciton in a bilayer quantum antiferromagnet, in the limit that the holon and doublon are strongly bound onto one interlayer rung by the Coulomb force. Upon using a rung linear spin wave approximation of the bilayer Heisenberg model, we…

Louk Rademaker, Jan Zaanen and Hans Hilgenkamp

Physical review. B, Condensed matter and materials physics 83 1, 012504 (2011)

Currently a way is lacking to detect unambiguously the possible phase coherence of an exciton condensate in an electron-hole double layer. Here we show that despite the fact that excitons are charge-neutral, the double layer exciton superfluid exhibits a diamagnetic response. In devices with…