arXiv subjects

Minho Luke Kim

Publications and source records attributed to Minho Luke Kim.

4 recordsLinked to original sources

arXiv2026

Symmetry-Enforced Fermi Surfaces

We identify a symmetry that enforces every symmetric model to have a Fermi surface. These symmetry-enforced Fermi surfaces are realizations of a powerful form of symmetry-enforced gaplessness. The symmetry we construct exists in quantum lattice fermion models on a $d$-dimensional Bravais lattice, and is generated by the on-site U(1) fermion number symmetry and non-on-site Majorana translation symmetry. The resulting symmetry group is a noncompact Lie group closely related to the Onsager algebra. For a symmetry-enforced Fermi surface $\cal{F}$, we show that this UV symmetry group always includes the subgroup of the ersatz Fermi liquid L$_{\cal{F}}$U(1) symmetry group formed by even functions ${f(\mathbf{k})\in\mathrm{U}(1)}$ with ${\mathbf{k}\in \cal{F}}$. Furthermore, we comment on the topology of these symmetry-enforced Fermi surfaces, proving they generically exhibit at least two noncontractible components (i.e., open orbits).

cond-mat.str-el↗

arXiv2026

Shape of Wigner Crystals and Hole Self-Doping in a Mexican-Hat Dispersion

We study Wigner crystals (WCs) induced by a strong Coulomb interaction from the ring-like Fermi surface of a Mexican-hat dispersion $ε_k= c_2k^2+c_4k^4$. We design orbital shape in order to minimize the energy of the WC, and find that a low ground-state energy requires an orbital shape with a depletion of electrons near $k=0$. To capture the Coulomb-induced correlations, we include a Jastrow factor as well as a factor describing the correlation between electrons and doped vacancies. Using variational Monte Carlo calculations, we calibrate the effective band parameters $c_2$ and $c_4$ to reproduce the two transitions observed experimentally as the electron density is lowered: from a spin-valley-polarized Fermi liquid with a disk-like Fermi surface, to one with a ring-like Fermi surface, and finally to a WC. We find that, even with an optimized orbital shape that depletes electrons near $k=0$, a WC with hole self-doping near $k=0$ can still be energetically favorable near the WC transition, provided that the electron-vacancy correlation is included. We also estimate the dispersion of the doped hole.

cond-mat.str-el↗

arXiv2026

Variational Monte Carlo Optimization of Topological Chiral Superconductors

We perform the variational Monte Carlo calculation for recently proposed chiral superconducting states driven by strong Coulomb interactions. We compare the resulting energetics of these electronic phases for the electron dispersion relation $E_k = c_2 k^2+c_4 k^4$. Motivated by the recent discovery of chiral superconductivity in rhombohedral graphene systems, we apply our analysis to relevant parameter regimes. We demonstrate that topological chiral superconducting phases (including a spin-unpolarized state) can be energetically favored over the spin-valley polarized Fermi liquid above the density of Wigner crystal phase. Our results show that the preference for chiral superconductivity is strongest when $c_2$ lies between zero and a negative value corresponding to a Fermi sea on the verge of forming a hole pocket around $k=0$. This finding suggests that superconductivity can arise from pure repulsive Coulomb interactions in systems with an almost flat band bottom, without relying on the pairing instability of a Fermi surface. This mechanism opens a new pathway to superconductivity beyond the conventional BCS mechanism.

cond-mat.str-el↗

arXiv2025

Parity anomaly from LSM: exact valley symmetries on the lattice

We show that the honeycomb tight-binding model hosts an exact microscopic avatar of its low-energy SU(2) valley symmetry and parity anomaly. Specifically, the SU(2) valley symmetry arises from a collection of conserved, integer quantized charge operators that obey the Onsager algebra. Along with lattice reflection and time-reversal symmetries, this Onsager symmetry has a Lieb-Schultz-Mattis (LSM) anomaly that matches the parity anomaly in the IR. Indeed, we show that any local Hamiltonian commuting with these symmetries cannot have a trivial unique gapped ground state. We study the phase diagram of the simplest symmetric model and survey various deformations, including Haldane's mass term, which preserves only the Onsager symmetry. Our results place the parity anomaly in ${2+1}$D alongside Schwinger's anomaly in ${1+1}$D and Witten's SU(2) anomaly in ${3+1}$D as 't Hooft anomalies that can arise from the Onsager symmetry on the lattice.

cond-mat.str-el↗