Periodic Reporting for period 2 - SimUcQuam (Simulating ultracold correlated quantum matter: New microscopic paradigms)
Periodo di rendicontazione: 2023-05-01 al 2024-10-31
The goal of the SimUcQuam project is to reveal the microscopic structure of emergent charge carriers of doped quantum magnets: These systems play an important role in the context of strongly correlated electrons, constituting the basis for some of the most fascinating and promising material properties observed in nature. In particular, this includes high-temperature superconductors — materials that conduct electric current free of any loss of energy, up to technologically easily accessible temperature scales. Despite decades of research aiming to reveal the physical mechanisms underlying the peculiar electronic properties of these materials, no generally accepted theoretical picture exists to date. This hinders the development of new materials, that may feature even higher critical superconducting temperatures, and would be of significant technological relevance. Indeed such materials may help battle climate change by enabling lossless transport of green energies of potentially long distances.
In the SimUcQuam project, we investigate these strongly correlated electronic systems from a new perspective, with the help of quantum simulators. We study the conceptually simplest — yet poorly understood — theoretical models describing strongly correlated electrons. Our main research objective is to reveal the microscopic structure of charge carriers in these systems. To this end we propose new types of table-top experiments that can uncover hidden structures and reveal the collective excitations of these strongly correlated electronic systems. Based on the obtained insights, our main goal is to describe how the rich internal structure of the charge carriers can give rise to strong — potentially attractive — interactions that ultimately underly high-temperature superconductivity and the nearby correlated phases.
In the SimUcQuam project, we investigate these strongly correlated electronic systems from a new perspective, with the help of quantum simulators. We study the conceptually simplest — yet poorly understood — theoretical models describing strongly correlated electrons. Our main research objective is to reveal the microscopic structure of charge carriers in these systems. To this end we propose new types of table-top experiments that can uncover hidden structures and reveal the collective excitations of these strongly correlated electronic systems. Based on the obtained insights, our main goal is to describe how the rich internal structure of the charge carriers can give rise to strong — potentially attractive — interactions that ultimately underly high-temperature superconductivity and the nearby correlated phases.
Since the start of the SimUcQuam project, we have characterized and theoretically modeled the internal structure of charge carriers in different types of doped quantum antiferromagnets. Moreover, we have made significant progress in understanding and characterizing new pairing mechanisms that may arise in these systems, as a direct result of the rich internal structure of the charge carriers. A particular highlight of our research includes the prediction of strong pairing, mediated by strings, in mixed-dimensional antiferromagnets. In a collaboration with the experimental group of Prof. Immanuel Bloch, this has led to the first-ever direct observation of paired dopants in a cold atom quantum simulator. We have further proposed in a series of publications that the pairing mechanism we put forward may underly high-temperature superconductivity recently observed in bilayer niceklates under pressure.
We have then applied our results and insights to the long-standing problem of high-temperature superconductivity in the cuprate compounds, which led us to the formulation of the so-called Feshbach hypothesis of high-Tc. Namely, we propose that the unusually high superconducting temperatures in the cuprates may be a result of near-resonant interactions between fermionic charge carriers with an internal structure, mediated by tightly string-bound pairs of dopants. We have shown that this hypothesis is able to explain some of the key properties of the cuprate superconductors.
Maybe even more importantly, we then discovered that the same hypothesis may apply to the newly discovered bilayer nickelate superconductors: Thereby our theoretical mechanism is able to provide a unifying explanation how superconductivity arises at high temperatures in these seemingly distinct material classes.
In parallel, we have made significant advances in understanding how various collective many-body phases of matter arise in strongly correlated fermions with antiferromagnetic interactions. In another collaboration with the experimental group of Prof. Immanuel Bloch we have discovered the formation of individual stripes, involving correlated structures of multiple dopants, in an extended mixed-dimensional Hubbard model, at relatively high temperatures. To formulate effective theories of such collective phenomena, we have developed lattice gauge theory descriptions and quantum simulation protocols for the latter.
We have then applied our results and insights to the long-standing problem of high-temperature superconductivity in the cuprate compounds, which led us to the formulation of the so-called Feshbach hypothesis of high-Tc. Namely, we propose that the unusually high superconducting temperatures in the cuprates may be a result of near-resonant interactions between fermionic charge carriers with an internal structure, mediated by tightly string-bound pairs of dopants. We have shown that this hypothesis is able to explain some of the key properties of the cuprate superconductors.
Maybe even more importantly, we then discovered that the same hypothesis may apply to the newly discovered bilayer nickelate superconductors: Thereby our theoretical mechanism is able to provide a unifying explanation how superconductivity arises at high temperatures in these seemingly distinct material classes.
In parallel, we have made significant advances in understanding how various collective many-body phases of matter arise in strongly correlated fermions with antiferromagnetic interactions. In another collaboration with the experimental group of Prof. Immanuel Bloch we have discovered the formation of individual stripes, involving correlated structures of multiple dopants, in an extended mixed-dimensional Hubbard model, at relatively high temperatures. To formulate effective theories of such collective phenomena, we have developed lattice gauge theory descriptions and quantum simulation protocols for the latter.
In the second part of the SimUcQuam project, we will focus our attention on the collective phases of matter arising from the interplay of individual dopants in an antiferromagnetic background. On one hand, we expect to be able to clarify whether near-unitary interactions between doped holes — mediated by a Feshbach resonance — play a role for understanding the superconducting dome observed in cuprate compounds. On the other hand, we will study hidden antiferromagnetic order arising in the context of fluctuations stripes: This regime is becoming increasingly more accessible both numerically and for ultracold atom experiments. The theoretical formalism we will employ is based on effective Z2 lattice gauge theories with and without matter, in which we will continue to study experimentally friendly confinement order parameters. To investigate the universal phase diagrams of these models, we will also continue to analyze the possibility of performing quantum simulation experiments of the latter.
Other expected result concern spectroscopic probes of the internal structure of charge carriers, in particular in pair spectroscopy, accessible to ultracold atom and solid state experiments in state-of-the-art experiments.
Other expected result concern spectroscopic probes of the internal structure of charge carriers, in particular in pair spectroscopy, accessible to ultracold atom and solid state experiments in state-of-the-art experiments.