Session G44: Physical Review Invited Session: Forefront Research Across Disciplines

Physically Optimal Solar Resource Efficiency in Giant Clams

Living photosynthetic systems can be near-perfectly efficient at solar energy conversion at small length- and time-scales. However, they are very inefficient (~3%) at the scale of crops or ecosystems. Is it physically possible to realize the near-perfect efficiencies of photosynthesis at a small scale over large land areas? Answering this question is crucial for reducing economic reliance on fossil fuels. We created a simple model of a "solar transformer" that was inspired by the geometry of symbiotic giant clams that host single-celled algae in their tissues. We found a straightforward, general mechanism to achieve a photosynthetic light-use efficiency of 67% of the solar radiance in an average tropical day. Remarkably, living clams may exceed this efficiency, and we describe the mechanical mechanisms that may allow this.   

Quantum Biology: How nature harnesses quantum processes to function optimally, and how might we control such quantum processes to therapeutic and tech advantage

Imagine driving cell activities to treat injuries and disease simply by using tailored magnetic fields. Many relevant physiological processes, such as: the regulation of oxidative stress, proliferation, and respiration rates in cells; wound healing; ion channel functioning; and DNA repair were all demonstrated to be controlled by weak magnetic fields (with a strength on the order of that produced by your cell phone). Such macroscopic physiological responses to magnetic fields are consistent with being driven by chemical reactions that depend on the electron quantum property of spin. In the long-term, the electromagnetic fine-tuning of endogenous "quantum knobs" existing in nature could enable the development of drugs and therapeutic devices that could heal the human body — in a way that is non-invasive, remotely actuated, and easily accessible by anyone with a mobile phone. However, whereas spin-dependent chemical reactions have been unambiguously established for test-tube chemistry (bearing uncanny similarities with what physicists call "spin quantum sensing"), current research has not been able to deterministically link spin states to physiological outcomes in vivo and in real time. With novel quantum instrumentation, we are learning to control spin states within cells and tissues, having as a goal to write the "codebook" on how to deterministically alter physiology with weak magnetic fields to therapeutic and technological advantage.   

Quantum Error Correction Codes as Exotic Quantum Matter

To achieve more robust computation and communication processes with quantum information, quantum error correction codes were invented to protect the information from noise and decoherence. The codes consist of specifically designed, contrived quantum states, yet some of them have become hot topics in condensed matter physics, an area traditionally grounded in measurable phenomena in real world solid state materials. This talk will explain how these error correction codes reveal possible novel physics phenomena and inspire the exploration of new phases in condensed matter system. At the same time, connecting them to real experimental system provides a path forward to realizing robust information processing protocols.   

Kekule Spirals in Twisted Graphene Multilayers

One of the major challenges in the study of magic angle twisted bilayer graphene  (MATBG) has been the understanding the insulating states that arise as a result of inter-electron interaction.   A combination of recent theoretical [1,2,3,4] and experimental [5,6] work has now established the presence of a new type of order which we call "Incommensurate Kekule Spiral" (IKS) order.   This order spontaneously breaks both the valley-charge conservation and moiré translation symmetries, but preserves a modified translation symmetry which simultaneously shifts the spatial coordinates and rotates the U(1) angle which characterizes the spontaneous inter-valley coherence.  This type of order appears ubiquitous in the presence of miniscule amounts of strain at temperatures above the superconducting transitions.    In this talk I will give an introduction to the physics of MATBG emphasizing the strong coupling approximations.  I will then turn to the Hartree-Fock calculations we used to predict the IKS order and I will explain the physics that drives the system towards this ground state.   I will also briefly discuss the experiments that have observed this phase, the competing phases that are observed in ultra-small strain samples, as well as the closely related physics of magic angle trilayer graphene.

[1]  Yves H. Kwan, Glenn Wagner, Tomohiro Soejima, Michael P. Zaletel, Steven H. Simon, Siddharth A. Parameswaran, Nick Bultinck,  Phys. Rev. X 11, 041063 (2021)

[2]  Glenn Wagner, Yves H. Kwan, Nick Bultinck, Steven H. Simon, S. A. Parameswaran, Phys. Rev. Lett. 128, 156401 (2022)

[3]  Yves H. Kwan, Glenn Wagner, Nick Bultinck, Steven H. Simon, Erez Berg, S. A. Parameswaran,  arXiv:2303.13602 

[4] Tianle Wang, Daniel E. Parker, Tomohiro Soejima, Johannes Hauschild, Sajant Anand, Nick Bultinck, and Michael P. Zaletel, PRB accepted (2023)

[5]  Kevin P. Nuckolls et al,  Nature 620, 525-532 (2023)

[6]  Hyunjin Kim, et al, arXiv:2304.10586   

Anyons in the fractional quantum Hall effect

A basic tenet of quantum theory is that all elementary particles are either bosons or fermions. Ensembles of bosons or fermions behave differently due to differences in their underlying quantum statistics. Starting in the early 1980’s it was theoretically conjectured that excitations that are neither bosons nor fermions may exist under special conditions in two-dimensional interacting electron systems. These unusual excitations were dubbed “anyons”. Anyons possess fractional charge and fractional statistics, however directly probing these properties presents experimental challenges. This lecture will focus on the development of electronic Fabry-Perot interferometers that resulted in the first direct observation of anyonic braiding statistics in the fractional quantum Hall state at ν=1/3. These experiments have now been extended to the more fragile multi-edge-mode hierarchy state at ν=2/5. Application of interferometry to the putative non-abelian state at ν=5/2 will be discussed.