Bulletin of the American Physical Society
APS March Meeting 2024
Monday–Friday, March 4–8, 2024; Minneapolis & Virtual
Session T41: Emergence and Design of Fractals in Quantum MaterialsInvited
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Sponsoring Units: DCMP Chair: Marlou Slot, National Institute of Standards and Technology Room: Ballroom A |
Thursday, March 7, 2024 11:30AM - 12:06PM |
T41.00001: Quantum Fractals: from meta- to real-materials Invited Speaker: Cristiane Morais Smith We know how electrons behave in 1,2,3 dimensions, but what about d=1.58? In this talk, I will first describe fractals, structures that may have a non-integer dimension. Then I will present experiments on electronic [1] and photonic [2] quantum simulators and explain how electrons and photons behave at fractal dimension. Finally, I will discuss the fractal-lattice Hubbard model [3] and the topological properties of electrons in self-formed bismuth fractals on InSb [4]. |
Thursday, March 7, 2024 12:06PM - 12:42PM |
T41.00002: Dynamic Fractals in Spin Ice Invited Speaker: Claudio Castelnovo Fractals -- objects with non-integer dimensions -- occur in manifold settings and length scales in nature, ranging from snowflakes and lightning strikes to natural coastlines. Much effort has been expended to generate and study fractals in many-body physics, oftentimes underpinned by the presence of disorder. Here, we identify an emergent dynamical fractal in a disorder-free, stoichiometric three-dimensional magnetic crystal in thermodynamic equilibrium. The phenomenon is borne out of constraints on the dynamics of the microscopic degrees of freedom imposed by the topological nature of the system and by its characteristic point-like excitations, which at low temperatures become restricted to move on the fractal. This observation explains the anomalous exponent found in magnetic noise experiments on Dy$_2$Ti$_2$O$_7$, and it resolves a long standing puzzle about its rapidly diverging relaxation time. This is a case in point of the capacity of even simple topological many-body systems to exhibit striking phenomena in their cooperative dynamics, and of the promise they hold for further surprising discoveries. |
Thursday, March 7, 2024 12:42PM - 1:18PM |
T41.00003: Universal Features of Emergent Electronic Fractals in Quantum Materials Invited Speaker: Erica W Carlson Electrons inside of many quantum materials spontaneously form clumpy patterns on multiple length scales. By importing techniques from disordered statistical mechanics into the field of quantum materials, we have defined new conceptual frameworks for understanding and controlling this electronic inhomogeneity. This allows us to use the rich information available from spatially resolved probes to diagnose criticality from the spatial structure alone, without the need of a sweep of temperature or external field. These new methods have enabled the discovery of universal, fractal electronic textures across a variety of quantum materials. For instance, scanning tunneling microscopy on BSCO reveals that the orientations of electronic stripes in that material form fractal, self similar patterns displaying power law behavior throughout the superconducting doping range [1], leading to a connected scaffolding on which superconductivity can arise. Surprisingly similar structures are also found in antiferromagnetic domains in NdNiO3 and the Mott metal-insulator transition in VO2. In NdNiO3, scanning resonant magnetic X-ray scattering reveals a highly textured magnetic fabric, establishing a self-similar network of antiferromagnetic domains [2]. In VO2, both scanning near-field optical microscopy and far-field optical microscopy have revealed that as opposed to transitioning from insulator to metal all at once, VO2 forms an intricate, fractal network of metallic puddles that extend like filigree over a wide range of temperatures [3]. This identification opens the door to using hysteresis effects to sculpt the filigree, in order to improve the function of VO2 in novel electronic applications such as neuromorphic devices and quantum sensing. The universal features of these fractal electronic textures across a disparate collection of quantum materials hints at a common origin. We show that this emergent electronic complexity is the result of proximity to a critical point arising from the combined effects of quenched disorder and interactions. |
Thursday, March 7, 2024 1:18PM - 1:54PM |
T41.00004: Topological phases on fractal Lattices: Constructions and bulk-boundary correspondence Invited Speaker: Bitan Roy Topological crystals, described by universal massive Dirac-Bloch Hamiltonian, feature robust gapless modes at their interfaces (edge, surface, hinges and corners), encoding nontrivial geometry of bulk electronic wavefunctions. However, nature also fosters non-crystalline (a) amorphous materials with no symmetry at all, (b) quasicrystals with only rotational symmetry, and (c) fractals displaying unique self-similarity symmetry. It is, therefore, of fundamental importance to investigate the possibility of realizing topological phases on such material platforms, where the Bloch’s theorem does not apply, due their recent realizations on designer quantum materials and classical metamaterials, such as the topolectric circuits and mechanical lattices. |
Thursday, March 7, 2024 1:54PM - 2:30PM |
T41.00005: Fractal Magnetic Textures in Rare Earth Nickelates Invited Speaker: Jiarui Li Correlated electron systems often manifest emergent quantum phenomena at the macroscale. Many emergent quantum electronic phases are inherently inhomogeneous due to the presence of competing degrees of freedom near phase boundaries. The macroscopic properties of quantum materials are largely dependent on the microscopic organizing principle of the electronic textures. One example is near a critical point, where electrons tend to organize into self-similar patterns that look the same at all length scales. The resulting fractal geometry is a hallmark of criticality. |
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