2026 Simons Collaboration on New Frontiers in Superconductivity Annual Meeting

Thursday, November 12

Friday, November 13

Daniel Agterberg
University of Wisconsin–Milwaukee

Superconductivity and Local Inversion Symmetry Breaking: Applications to Monolayer FeSe and UTe2

Monolayer FeSe and UTe 2 are two superconductors that have generated tremendous interest: monolayer FeSe for its high transition temperature and UTe 2 for its remarkable high-field superconductivity. Here, Daniel Agterberg presents the results of two experiment-theory collaborations that reveal important insights into both materials. In superconducting monolayer FeSe, local density of states (DOS) measurements reveal a particle-hole asymmetry that changes sign at the two Fe sites in the unit cell. In this talk, Agterberg finds the origin of this asymmetry and shows how this identifies the likely pairing symmetry. In UTe 2, ultrasound measurements reveal a pressure-induced strongly fluctuating superconducting state, with a fluctuation regime larger than any known 3D superconductor. Agterberg proposes an unusual odd-parity superconductivity for UTe 2 and shows how this state also naturally accounts for high-field reentrant superconductivity. For both these materials, a key feature that underlies the theory is that the relevant atomic positions locally break inversion symmetry.

Erez Berg
University of California Santa Barbara

Stability and Relaxation of Strongly Coupled Electron-Phonon Systems

In this talk, Erez Berg studies the kinetic properties of Migdal–Eliashberg theory (MET) for electron-phonon interactions at strong-coupling. Previously, the system was found to be dynamically unstable at large couplings within a Markovian Boltzmann approximation. Using the quasiclassical Kadanoff–Baym equation, Berg shows that this instability is absent when non-Markovian effects are taken into account. Having established the validity of the strong-coupling limit, analyzing the long-time relaxation dynamics shows a clear imprint of the non-Markovian nature of the dynamics: in an intermediate temperature range between the Debye frequency and the coupling strength, the relaxation rate becomes linear in temperature with Planckian slope, while the leading relaxation mode acquires a large imaginary component, producing strongly oscillatory decay. These results imply that any instability which preempts superconductivity must arise from effects beyond MET, such as phonon softening or finite electronic bandwidth polaronic effects. This leaves open the possibility of parametrically unbounded superconducting $T_c$ in multi-flavor electron-phonon models.

Laura Classen
Max Planck Institute for Solid State Research

Superconductivity from Repulsive Interactions in tWSe2

Motivated by the observation of superconductivity in twisted bilayer WSe2 for an extended range of displacement field between a correlated insulator and zero, in this talk, Laura Classen performs an instability analysis of tWSe2 at hole filling -1 and twist angle 3.65° using the functional renormalisation group. Classen compares the instabilities obtained from a continuum model with Coulomb interaction and a three-orbital Wannier model with Hubbard interaction, which is derived from first principles. In both cases, Classen finds a superconducting instability with a mixed d-wave singlet and p-wave triplet symmetry arising adjacent to inter-valley coherent spin density wave order in the phase diagram for varying displacement field and interaction strength. While the pairing mechanism is shown to be consistent with IVC spin fluctuations as pairing glue, the size and critical temperatures of the pairing regime changes depending on the model input, and Classen argues that the main difference comes from the range and quantum geometry entering the projected interaction.

Dmitri Efetov
LMU Munich

Establishing a Sample-Independent Phase Diagram of Magic-Angle Twisted Bilayer Graphene

Magic-angle twisted bilayer graphene (MATBG) hosts a rich phase diagram arising from the interplay of flat bands, electronic correlations, and topology. However, microscopic device details, such as substrate, twist-angle inhomogeneity, and strain can strongly influence these phases, leading to device-to-device variability in the reported phase diagrams and limiting a unified understanding of MATBG. To address this challenge, Dmitri Efetov in this talk constructs a transport phase diagram of MATBG from an ensemble of 18 devices fabricated using the same protocol. By measuring multiple devices and performing a systematic statistical analysis, Efetov identifies robust transport features in the filling–temperature and filling–magnetic-field phase diagrams that are reproducible across the device ensemble, establishing that: (i) above ∼ 10 K, all integer fillings display nearly symmetric semimetallic features; (ii) below ∼ 10 K, this symmetry is broken and activated transport occurs most robustly at ν = ±2, with higher activation temperature on the electron side; (iii) no insulating gaps occur at ν = ±1; (iv) superconductivity is mostly observed at ν = ±2 ± δ; (v) a metallic regime appears above these superconducting domes below 10 K; (vi) the resistivity evolves from approximately T 2 scaling near charge neutrality to linear-in-T scaling away from it, and extends to low temperature; and (vii) in out-of-plane magnetic field, Landau fans emerge from charge neutrality and ν = ±2, but not from ν = ±1. This work establishes the first statistically-validated transport phase diagram of MATBG, isolating robust phenomenology from device-specific features and providing a benchmark for future theoretical and experimental studies.

B. Andrei Bernevig
Princeton University

Superconductivity 2026

In this talk, B. Andrei Bernevig reviews the progress made on superconductivity in his group over the past year, both in twisted systems, but more importantly, in a new strong AI push for finding stable, novel, structures. Bernevig also presents personal views on what is needed from the collaboration in order to make progress on the central Tc question.

Kristjan Haule
Rutgers University

Toward a Predictive First-Principles Theory of Unconventional Superconductivity

Developing a truly predictive, materials-specific theory of unconventional superconductivity remains one of the central challenges in condensed matter physics. In this talk, Kristjan Haule presents recent progress toward this goal based on a fully charge-self-consistent DFT+cluster DMFT framework that treats strong electronic correlations directly from first principles. Building on recent work on multilayer cuprates, Haule demonstrates that the essential materials trends — including the evolution of the charge-transfer gap, superexchange, electronic structure, and superconducting order — can be quantitatively understood without relying on empirically parameterized low-energy models. Calculations reveal how quantum-confined conduction states control the evolution of superconductivity across multilayer cuprate families and establish a practical route toward materials-specific predictions.

Haule also discusses recent progress on identifying microscopic structural descriptors that control superconductivity, showing in partiuclar how the apical oxygen environment provides an efficient tuning parameter for the electronic structure and pairing interactions, which offers new insights into materials optimization. Finally, Haule presents ongoing work that extends the theory beyond the pairing amplitude by computing the superfluid stiffness from first principles. Combining the calculated pairing scale with the Berezinskii–Kosterlitz–Thouless criterion provides a direct route to predicting the superconducting transition temperature in quasi-two-dimensional cuprates. Together, these developments represent important steps toward a quantitative, parameter-free theory capable of predicting superconductivity in real correlated materials.

Joerg Schmalian
Karlsruhe Institute of Technology (KIT)

Stability and Relaxation of Strongly Coupled Electron-Phonon Systems

In this talk, Joerg Schmalian demonstrates that superconductivity driven by strong quantum-critical fluctuations can emerge near relativistic Mott transitions in twisted two-dimensional materials. In twisted double-bilayer WSe2, all timereversal-even, gap-opening collective modes promote pairing, whereas time-reversal-odd modes do not. In twisted bilayer graphene, all transitions into intervalley-coherent insulators give rise to superconductivity. Hence, the two separate superconducting domes of insulating or semimetallic undoped systems are expected to merge near the Gross–Neveu transition angle. A crucial ingredient of the theory is that critical fluctuations render the electronic states strongly incoherent, allowing attractive pairing channels to overcome the bare Dirac semimetal behavior. The richer the Dirac structure, the more readily pairs can form. Finally, Schmalian demonstrates a direct relation between boson-mediated pairing and the formation of charge-carrying skyrmions in the proximate insulating state.

Zhida Song
Peking University

Two Pairing Scenarios in Magic-Angle Twisted Bilayer Graphene

In this talk, Zhida Song discusses two pairing scenarios in magic-angle twisted bilayer graphene, distinguished by the role of the correlated f-electrons. Optical phonons generate an intervalley anti-Hund interaction among the f-electrons. At relatively large doping, the f-electrons hybridize with the itinerant c-electrons and participate in a large Fermi surface, forming a heavy Fermi liquid. The anti-Hund interaction is then inherited by the heavy quasiparticles and drives their pairing. At small doping, our variational Gutzwiller calculations reveal a distinct small-Fermi-liquid normal state. In this regime, the f-electrons do not participate in the Fermi surface and exhibit strongly suppressed charge fluctuations. Nevertheless, their internal multiplet excitations remain active: virtual multiplet excitons can mediate an effective attractive interaction between the itinerant c-electrons. Song establishes a Migdal theorem for these multiplet excitons and develops an Eliashberg theory of the resulting superconductivity. Together, heavy-Fermi-liquid pairing at large doping and multiplet-exciton-mediated pairing at small doping provide a natural explanation for the superconducting dome observed experimentally.

Participation in the meeting falls into the following four categories. An individual’s participation category is communicated via their letter of invitation.

The Simons Foundation will never ask for credit card information or require payment for registration to our events.

Group A – PIs, Speakers & Organizers

Individuals in Group A receive travel and hotel coordination within the following parameters:

Travel
Economy Class: For flights that are three hours or less to your destination, the maximum allowable class of service is Economy class.
Premium Economy Class: For flights where the total air travel time (excluding connection time) is more than three hours and less than seven hours per segment to your destination, the maximum allowable class of service is premium economy.
Business Class: When traveling internationally (or to Hawaii/Alaska) travelers are permitted to travel in Business Class on those segments that are seven hours or more. If the routing is over budget, a premium economy or mixed-class ticket will be booked.

Hotel
Up to 3 nights at the conference hotel, arriving on Wednesday, November 11 and departing on Saturday, November 14.

Group B – Funded Participants

Individuals in Group B receive travel and hotel coordination within the following parameters:

Travel
Economy class travel will be booked regardless of flight length.

Hotel
Up to 3 nights at the conference hotel, arriving on Wednesday, November 11 and departing on Saturday, November 14.

Group C – Unfunded Participants

Individuals in Group C will not receive financial support but are encouraged to enjoy all conference-hosted meals.

Group D – Remote Participants

Individuals in Group D will participate in the meeting remotely.

Air and Rail

For funded individuals, the foundation will arrange and pay for round-trip travel from their home city to the conference city. All travel and hotel arrangements must be booked through the Simons Foundation’s preferred travel agency.

Travel Deviations

The following travel specifications are considered deviations and will only be accommodated if the cost is less than or equal to the amount the Simons Foundation would pay for a standard round-trip ticket from your home city to the conference city:

• Preferred airline
• Preferred travel class
• Specific flights/flight times
• Travel dates outside those associated with the conference
• Arriving or departing from an airport other than your home city or conference city airports, i.e. multi-segment or triangle trips.

All deviations must be reviewed and approved by the Simons Foundation and, if the cost is more than what would normally be paid, a reimbursement quote must be obtained through the foundation’s travel agency before proceeding to booking and paying for travel out of pocket. All reimbursements for travel booked directly will be paid after the conclusion of the meeting.

Changes After Ticketing

All costs related to changes made to ticketed travel are to be paid for by the participant and are not reimbursable. Please contact the foundation’s travel agency for further assistance.

Personal & Rental Cars

Personal car and rental trips over 250 miles each way require prior approval from the Simons Foundation via email.

Rental cars must be pre-approved by the Simons Foundation.

The Hotel Seville NoMad offers valet parking. Please note there are no in-and-out privileges when using the hotel’s garage, therefore it is encouraged that participants walk or take public transportation to the Simons Foundation.

Hotel

Funded individuals who require hotel accommodations are hosted by the foundation for a maximum of 3 nights at the conference hotel, arriving on Wednesday, November 11 and departing on Saturday, November 14.

Any additional nights are at the attendee’s own expense. To arrange accommodations, please register at the link included in your invitation.

Hotel Seville NoMad
22 E 29th St
New York, NY 10016
(between 28th and 29th Streets)
https://www.hyatt.com/unbound-collection/en-US/nycud-hotel-seville-nomad

For driving directions to the Hotel Seville NoMad, please click here.

Overview

In-person participants will be reimbursed for meals and local expenses including ground transportation. Expenses should be submitted through the foundation’s online expense reimbursement platform after the meeting’s conclusion.

Expenses accrued because of meetings not directly related to the Simons Foundation-hosted meeting (a satellite meeting or meeting held at another institution, for example) will not be reimbursed by the Simons Foundation and should be paid by other sources.

Below are key reimbursement takeaways; a full policy will be provided with the final logistics email circulated approximately 2 weeks prior to the meeting’s start.

Meals

The daily meal limit is $125; itemized receipts are required for expenses over $24 USD. The foundation DOES NOT provide a meal per diem and only reimburses actual meal expenses up the following amounts.

• Breakfast $20
• Lunch $30
• Dinner $75

Allowable Meal Expenses

• Meals taken on travel days (when you traveled by air or train).
• Meals not provided on a meeting day, dinner on Friday for example.
• Group dinners consisting of fellow meeting participants paid by a single person will be reimbursed up to $75 per person and the amount will count towards the $125 daily meal limit.

Unallowable Meal Expenses

• Meals taken outside those provided by the foundation (breakfast, lunch, breaks and/or dinner).
• Meals taken on days not associated with Simons Foundation-coordinated events.
• Minibar expenses.
• Meal expenses for a non-foundation guest.

• Ubers, Lyfts, taxis, etc., taken to and from restaurants in Manhattan.

  • Accommodations will be made for those with mobility restrictions.

Ground Transportation

Expenses for ground transportation will be reimbursed for travel days (i.e. traveling to/from the airport or train station) as well as subway and bus fares while in Manhattan are reimbursable.

Transportation to/from satellite meetings are not reimbursable.

Attendance

In-person participants and speakers are expected to attend all meeting days. Participants receiving hotel and travel support wishing to arrive on meeting days which conclude at 2:00 PM will be asked to attend remotely.

Entry & Building Access

Upon arrival, guests will be required to show their photo ID to enter the Simons Foundation and Flatiron Institute buildings. After checking-in at the meeting reception desk, guests will be able to show their meeting name badge to re-enter the building. If you forget your name badge, you will need to provide your photo ID.

The Simons Foundation and Flatiron Institute buildings are not considered “open campuses” and meeting participants will only have access to the spaces in which the meeting will take place. All other areas are off limits without prior approval.

If you require a private space to conduct a phone call or remote meeting, please contact your meeting manager at least 48-hours ahead of time so that they may book a space for you within the foundation’s room reservation system.

Guests & Children

Meeting participants are required to give 24-hour advance notice of any guests meeting them at the Simons Foundation either before or after the meeting. Outside guests are discouraged from joining meeting activities, including meals.

With the exception of Simons Foundation and Flatiron Institute staff, ad hoc meeting participants who did not receive a meeting invitation directly from the Simons Foundation are not permitted.

Children under the age of 18 are not permitted to attend meetings at the Simons Foundation. Furthermore, the Simons Foundation does not provide childcare facilities or support of any kind. Special accommodations will be made for nursing parents.

Meeting & Policy Questions

Meghan Fazzi
Senior Manager, Events & Administration
[email protected]

Travel & Hotel Support

FCM Travel Meetings & Events
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