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Department of Physics

The Cavendish Laboratory
 

This series of colloquia in the Cavendish Laboratory aims to cover all aspects of modern quantum many-body physics. It is broadly aligned with our research themes on Theoretical Condensed Matter PhysicsFundamental Physics of Quantum MatterApplied Quantum Physics and DevicesSynthetic Quantum SystemsQuantum Information and Control, and Energy Materials

As such, it features talks on both fundamental many-body physics as well as their exploitation in devices, covering all aspects of quantum phenomena in condensed matter and synthetic many-body systems, and their theoretical description.

The aim for these colloquia is to be accessible to a wider audience compared to a typical group seminar, and everyone is most welcome to attend them!

Click below to see details of the upcoming and previous talks. Please check this page regularly to keep informed as speakers are confirmed and details of their talks are added to the list.


Upcoming talks:

13 January 2025 at 15:00: Prof. Martin Zwierlein (MIT)

Venue: Small Lecture Theatre

Title: Fermion pairs and loners under the microscope
 

22 January 2025 at 16:15: Prof. Rachel Oliver (Materials)

Venue: Small Lecture Theatre

Title: Porous nitride semiconductors for novel light sources

Abstract: Porous semiconducting nitrides are effectively a new class of semiconducting material, with properties distinct from the monolithic nitride layers from which devices from light emitting diodes (LEDs) to high electron mobility transistors are increasingly made. The introduction of porosity provides new opportunities to engineer a range of properties including refractive index, thermal and electrical conductivity, stiffness and piezoelectricity. Quantum structures may be created within porous architectures and novel composites may be created via the infiltration of other materials into porous nitride frameworks. A key example of the application of porous nitrides in photonics is the fabrication of high reflectivity distributed Bragg reflectors (DBRs) from alternating layers of porous and non-porous GaN.  These reflectors are fabricated from epitaxial structures consisting of alternating doped and undoped layers, in which only the conductive, doped layers are electrochemically etched. Conventionally, trenches are formed using a dry-etching process, penetrating through the multilayer, and the electrochemical etch then proceeds laterally from the trench sidewalls.  The need for these trenches then limits the device designs and manufacturing processes within which the resulting reflectors can be used. We have developed a novel alternative etching process, which removes the requirement for the dry-etched trenches, with etching proceeding vertically from the top surface through channels formed at naturally-occurring defects in the crystal structure of GaN (see Figure). This etch process leaves an undoped top surface layer almost unaltered and suitable for further epitaxy. This new defect-based etching process provides great flexibility for the creation of a variety of sub-surface porous architectures on top of which a range of devices may be grown.  Whilst DBR structures enable improved light extraction from LEDs and the formation of resonant cavities for lasers and single photon sources, recent development also suggests that thick, sub-surface porous layers may enable strain relaxation to help improve the efficiency of red microLEDs for augmented reality displays.  Meanwhile, the option of filling pores in nitride layers with other materials provides new opportunities for the integration of nitrides with emerging photonic materials, such as the hybrid-perovskite semiconductors, with perovskites encapsulated in porous nitride layers demonstrating greatly improved robustness against environmental degradation.

 

5 February at 16:15: Prof. Frank Pollmann (TU Munich)

Venue: Small Lecture Theatre

Title: Exploring Quantum Phases of Matter on Quantum Processors

Abstract: Quantum fluctuations and interactions give rise to exotic phases of matter with remarkable properties, pushing the boundaries of our understanding of many-body quantum systems. Solving these problems is notoriously difficult on classical computers due to the exponential complexity of quantum many-body physics. Quantum processors, however, open new avenues for exploring these systems, offering a direct and potentially transformative approach. In this talk, I will first outline recent progress in realizing and studying topologically ordered and symmetry-protected phases using quantum hardware. I will then discuss their intriguing dynamical properties and how these can reveal quantum phase transitions. Finally, I will introduce a class of novel, highly entangled quantum phases that exist only in non-equilibrium settings and demonstrate how to probe their stability using a quantum processor.

19 February at 16:15: Prof. Michael Tarbutt (Imperial College)

Venue: Small Lecture Theatre

Title: TBC

5 March at 16:15: Prof. Natalia Berloff (DAMPT)

Venue: Small Lecture Theatre

Title: TBC

Previous talks